ARBORIST STUDY GUIDE 2026-2027

Regular scouting, traps, and sampling show pest activity, and plant bloom stages or degree-day models predict when the pest is at its most vulnerable stage, so treatments can be timed well.

They tunnel under or into the bark, often attacking stressed trees. Signs include pitch tubes, fine boring dust (frass), and small round holes; ambrosia beetles introduce fungi that kill tissue.

They grow as hyphae and mycelium and spread by spores, entering through wounds, stomata, or direct penetration. Fungi cause leaf spots, cankers, wilts, rots, and decay.

Biotic problems usually affect one species and spread gradually. Abiotic problems often affect many species at once, follow site features such as a road or drainage line, and show sharp, uniform boundaries.

Viruses live inside host cells and spread through insect vectors, grafting, and propagation. Symptoms include mosaic or ringspot patterns, and there is no chemical cure, so infected plants are removed or tolerated.

Healthy deciduous trees usually refoliate after one defoliation, but repeated defoliation drains reserves and invites secondary pests. Conifers often die after severe defoliation because they refoliate poorly.

Cupped, twisted, or strapped leaves, often on many plant species near treated areas. Drift or root uptake of lawn herbicides (such as dicamba and 2,4-D) is a common source.

Take fresh tissue at the margin between healthy and affected parts, keep it cool and dry in a bag, and send it quickly with site details and history. Do not send dead or dried-out material.

Fungal leaf diseases favored by cool, wet spring weather. They are usually cosmetic on mature trees, and managed by good air circulation, sanitation (raking leaves), and resistant species.

Predators and parasitoids such as lady beetles, lacewings, syrphid fly larvae, and parasitic wasps that feed on pests. Avoiding broad-spectrum pesticides helps conserve them.

Practices such as choosing resistant species, right plant right place, proper planting, watering, mulching, pruning, and sanitation. They are the first line of defense and prevent many problems.

Frost cracks are vertical splits in the trunk caused by rapid temperature changes. Winter injury also includes late frost damage to new growth and winter desiccation of evergreens.

Abnormal growths stimulated by insects, mites, or microbes. Most are cosmetic and do not threaten the health of the tree, so treatment is rarely needed.

Honeydew is the sugary excretion of aphids, scales, and whiteflies. Sooty mold is a black fungus that grows on honeydew, so controlling the insect removes the source of both.

Steps to prove a pathogen causes a disease: it is found in every case, isolated in pure culture, causes the same disease when inoculated into a healthy host, and can be re-isolated from that host.

Handpicking, pruning out infested branches, removing egg masses, barriers and bands, traps, and water sprays. They are low risk, but labor-intensive on large trees.

Phytophthora is a water mold that rots roots in wet, poorly drained soils. Armillaria produces honey-colored mushrooms, white fungal mats under bark, and black rhizomorphs, and attacks stressed trees.

Rusts produce orange or rusty spores and need two different host plants to complete their life cycle. Cedar-apple rust, for example, requires juniper and apple or crabapple.

Eight-legged arachnids, not insects, that feed on leaf cell contents and cause stippling and bronzing, often with fine webbing. They are favored by hot, dry weather and controlled by water sprays or miticides.

Identify the tree species, look at the whole site and tree history, look for patterns, check for signs and symptoms, consider biotic and abiotic causes, test if needed, and confirm the diagnosis before treating.

Wear the PPE required by the label, avoid drift and runoff, protect water and pollinators, mix and store products safely, dispose of waste by the label, and keep application records.

Inventory and assess the trees and site, set objectives, plan monitoring, choose cultural and other treatments, apply them, evaluate results, keep records, and communicate with the client.

Chewing insects (defoliators, leafminers), piercing-sucking insects (aphids, scales, lace bugs), borers that feed in the cambium and wood, and gall makers.

Marginal leaf scorch and dieback, usually on the side of the tree facing the road or on trees downslope from treated pavement. High soil salinity also damages roots.

Wilting, marginal leaf scorch, early fall color and leaf drop, small leaves, branch dieback, and increased susceptibility to borers and other secondary pests.

Pathogens such as Dutch elm disease, Verticillium wilt, and oak wilt that invade the xylem and block water movement. They cause sudden flagging of branches and may kill trees quickly.

The pinewood nematode, a microscopic roundworm carried by Monochamus sawyer beetles. Susceptible pines, such as Scots pine, wilt and turn brown rapidly and are usually removed.

A spiral or vertical strip of bark and wood blown off the trunk, which may be followed by decline, decay, or death. Lightning protection systems can be installed on valuable trees.

A localized area of dead bark and cambium, often sunken, that can girdle a stem. Many cankers develop on stressed trees via wounds, so reducing stress and pruning out cankers are standard treatments.

The pest population or damage level at which control becomes justified, based on tree value, tree health, and client tolerance for damage.

Biological control uses natural enemies or microbial products to reduce pests. Bacillus thuringiensis (Bt) is a bacterium that kills caterpillars that eat treated foliage and is safe for most other organisms.

An invasive beetle (Agrilus planipennis) that kills ash trees. Signs include D-shaped exit holes, S-shaped galleries under the bark, canopy thinning, bark splitting, and woodpecker damage.

A bacterial disease caused by Erwinia amylovora that infects members of the rose family such as apple, pear, and crabapple. Shoots wilt and blacken and bend into a shepherd's crook shape.

A decision-making approach that uses monitoring, thresholds, and a combination of cultural, physical, biological, and chemical tactics to manage pests with minimal risk to people and the environment.

A proactive, holistic approach to maintaining tree health that combines preventive practices, monitoring, accurate diagnosis, and appropriate treatment. It includes integrated pest management as one component.

A fungal disease producing a white powdery coating on leaves, favored by humid nights and dry days. It seldom threatens tree health, and resistant cultivars and good air flow reduce it.

A model in which predisposing factors (long-term stresses such as a poor site), inciting factors (short-term stresses such as drought or defoliation), and contributing factors (secondary organisms such as borers or Armillaria) combine to kill a tree.

A sign is the visible presence of the causal agent itself, such as a mushroom, conk, insect, or frass. A symptom is the tree's response to the problem, such as wilting, chlorosis, or cankers.

Biotic disorders are caused by living agents such as fungi, bacteria, insects, mites, nematodes, and parasitic plants. Abiotic disorders are caused by nonliving factors such as drought, frost, compaction, salt, herbicides, and mechanical injury.

Complete metamorphosis has egg, larva, pupa, and adult stages, with larvae that look different from adults (beetles, moths). Incomplete has egg, nymph, and adult stages, with nymphs resembling small adults (aphids, true bugs).

Systemics are absorbed and move within the tree, so they reach hidden or sucking pests. Contact products kill only what they touch. Application methods include foliar spray, soil drench or injection, and trunk injection.

White rot fungi break down lignin and cellulose, leaving bleached, stringy wood. Brown rot fungi break down cellulose, leaving brown, crumbly, cube-shaped residue.

A model showing that disease needs three things at the same time: a susceptible host, a pathogen, and a favorable environment. Removing or changing any one of them reduces disease.

Insecticides, miticides, fungicides, bactericides, herbicides, and nematicides. The label legally controls rates, targets, sites, and safety, and applicators must follow it exactly.

The crawler stage is the most vulnerable because it has no hard cover. Horticultural oils or insecticides applied when crawlers are active work much better than treatments on adult armored scales.

Not routinely. Research shows limited or inconsistent benefit, and some products can interfere with gas exchange. Proper watering and handling are far more important.

Usually not. Most soils already contain mycorrhizal fungi, and benefits from added inoculants have been inconsistent unless the soil has been severely disturbed or sterilized.

With the root flare at or slightly above the surrounding grade (1 to 2 inches higher in heavy soils). The tree should be set on firm, undisturbed soil so it does not settle deeper.

Container trees are removed from the pot, circling roots are loosened, straightened, or cut, and the outer root layer is scored or teased apart, so roots grow outward rather than around the trunk.

Probe the root ball and the surrounding soil by hand or with a probe or moisture meter. Overwatering is as harmful as underwatering, so water only when the root ball is drying.

ANSI Z60.1 sets minimum root ball diameter and depth by trunk caliper. For example, a 2-inch caliper tree needs about a 24-inch diameter root ball.

At 6 inches above the ground for trunks up to 4 inches in caliper, and at 12 inches above the ground for larger trunks, according to the American Standard for Nursery Stock.

Water thoroughly at planting, then frequently during the first weeks and less often as roots grow. Soak the root ball and surrounding soil; a rule of thumb is about one year of care per inch of trunk caliper.

Remove only dead, broken, or crossing branches and correct major structural problems. Keep the lower temporary branches that feed the trunk, and avoid heavy pruning or topping at planting.

Lift it by the root ball or container, never by the trunk. Protect the roots from drying, and avoid dropping or rolling the ball, which can break roots and damage the bark.

Spread 2 to 4 inches deep over the planting area, kept a few inches away from the trunk and root flare. It conserves moisture and reduces competition from turf and weeds.

Select species tolerant of wet soils, improve drainage if possible, and plant with the root ball set higher with soil banked to the edge. Avoid planting species intolerant of wet roots.

Large enough for the mature trunk and root flare, with removable or expandable grates so the trunk is not girdled. Larger pits and planting strips give the roots more space.

Generally no, unless a soil test shows a deficiency. Fertilizer can burn new roots and stimulate shoot growth before the roots are able to support it.

Generally no. Backfilling with the native soil encourages roots to grow out of the hole, while a rich amended pit can cause roots to stay inside or the hole to hold water. Amend the whole planting area only when soil is very poor.

Slow, deep applications such as drip, soaker hoses, or slow-release watering bags that wet the root ball and surrounding soil. Frequent shallow sprinkling encourages shallow roots.

Modular frames or cells that bear the weight of pavement above, leaving a large volume of uncompacted soil below for root growth. They provide more soil volume than structural soil.

They can be planted in almost any season and retain most of their roots. They may develop circling or pot-bound roots, which must be corrected at planting.

A tree spade moves large trees quickly with a root ball cut to size. The limits are that the root ball may be small for the tree, and the smooth blade can glaze the sides of the hole in clay soil.

They are lighter, less costly, and easy to inspect and shape the roots. They must be planted while dormant, kept moist, and installed quickly.

Stake and tie condition, watering and mulch, root flare exposure, pest and disease signs, dieback, and the need for corrective pruning. Inspections continue through the establishment period.

The standard practices for transplanting trees, including selection, handling, planting, and early care. It is a performance standard, and ISA Best Management Practices describe how to meet it.

The period in which the tree regrows enough roots to support the crown and begins normal growth. It ends when roots have extended well beyond the original root ball and shoot growth is consistent.

A field-grown tree dug with a ball of soil wrapped in burlap, often in a wire basket. Digging removes a large part of the root system, so these trees need careful handling and good watering.

A root that circles or crosses the trunk or other roots, compressing tissue and restricting water and sugar transport. It causes decline, a missing root flare, and a greater risk of stem failure.

The American Standard for Nursery Stock. It sets quality and size standards for nursery plants, including caliper, height, branching, and root ball dimensions, so buyers and growers use the same specifications.

An engineered mix of angular stone and soil (with a binder) that carries pavement loads while leaving pore space for roots. It is used under sidewalks and parking areas to expand rooting volume.

Bark injury caused when winter sun warms the trunk and the tissue then freezes at night. It occurs mainly on the south and southwest side of young, thin-barked trees.

Two to three times the width of the root ball, but no deeper than the root ball. Wide, shallow holes encourage roots to grow out into the surrounding soil.

Stress from loss of roots during digging and moving. Symptoms include wilting, leaf scorch, early fall color, slow growth, and dieback; proper handling, planting, and watering reduce it.

The root flare is buried, causing poor oxygen supply, bark decay at the trunk base, stem girdling roots, and slow decline. It is one of the most common causes of poor performance in new trees.

A visible root flare at the right level, no circling or girdling roots, a strong central leader with good taper, sound branch structure, no wounds or included bark, healthy foliage, and a root ball of adequate size.

Twine, rope, and synthetic materials should be removed, and the top one-third or more of the wire basket and burlap should be cut away or removed so they do not girdle roots or the trunk.

Call the utility locate service before digging (811 in the United States), check overhead clearance, grade, and drainage, test the soil, and relieve compaction in the planting area.

Only when the tree cannot stand alone, such as in windy or high-traffic sites. Use wide flexible ties that allow trunk movement, and remove stakes within about one year.

For large transplanted trees whose root balls cannot yet anchor the crown against wind. Anchors are installed with flexible, wide ties and removed after roots have established, usually within one to two years.

In the dormant season, either fall or early spring, when the weather is cool and moist and roots can grow without heavy demand from leaves. In hot climates the cool season is best.

Occasionally on thin-barked species for the first one or two winters to prevent sunscald and frost cracks. It should be removed in spring and is not needed in most situations.

Root pruning one to two seasons before digging encourages a compact, fibrous root system inside the root ball, which improves survival after transplanting.

They produce energy for the roots and trunk, add taper, and shade the trunk from sunscald. They are removed gradually over several years as the upper structure develops.

It defines tree quality, planting methods, aftercare, and the conditions for replacement, commonly for one year. It also documents the condition of the tree at installation.

Wounds at the trunk base can girdle the cambium and phloem and open the way to decay. Even partial girdling reduces growth and shortens the life of the tree.

Nursery trees often have extra soil or mulch over the flare. Remove it to find the true root flare, and set the flare, not the top of the ball, at grade.

They do not expand as branches and the trunk grow, so they can girdle and cut into the bark. Remove them at planting and check for any left on the tree during inspections.

Turf competes strongly with young roots for water and nutrients, and mowing and trimming can injure the trunk. A mulched bed several feet wide gives the roots room to establish.

No. They are designed for shearing hedges and leave stubs and ragged wounds on trees. Trees should be pruned with thinning and reduction cuts, not shearing.

No. They do not prevent decay or speed closure and may trap moisture. The exception is a wound paint applied to oaks cut during the oak wilt risk period to keep beetles away.

Pruning saws have teeth designed for cutting green wood, and many cut on the pull stroke. A curved blade gives better access to cuts at the branch collar.

Removing leaves reduces energy production, and removing buds or the terminal shoot redirects growth to the remaining buds, often causing vigorous sprouts. Heavy pruning triggers stronger regrowth.

A reduction cut shortens one stem to a lateral so the other becomes the dominant leader. In severe cases one stem is removed completely, ideally while the tree is young.

Select the strongest upright lateral near the top as the new leader and temporarily stake or tie it if needed. Subordinate or remove competing stems so only one dominant leader remains.

It follows the line from just outside the branch bark ridge to just outside the outer edge of the collar, so the cut is not parallel to the trunk. A flush cut parallel to the trunk removes the collar and protection zone.

No more than 25 percent of the foliage on a mature tree, with less on old or stressed trees. Larger amounts of removal weaken the tree by reducing energy production.

Structural pruning is usually done at planting and again every one to three years for the first several years, when the tree is small and the corrections are easy and small.

Just outside the collar of woundwood that has formed around the base of the dead branch, without cutting into the live callus tissue.

Reduce its weight first by removing parts, rig and lower it with ropes where needed, and use the three-cut method to prevent bark tearing and damage to the trunk or the target below.

About a quarter inch above the bud, sloping away from it so water runs off. Choose a bud facing the direction new growth is desired, usually outward.

Slightly wider at the base than at the top, so light reaches the lower foliage and keeps it full and healthy.

Cut at least 8 to 12 inches below visible symptoms, ideally in the dormant season. Disinfect tools between cuts to avoid spreading the bacteria.

Remove only dead, dying, or hazardous fronds. Palms have a single growing point and do not replace lost green fronds, so over-pruning (the hurricane cut) weakens them.

Spread vertically and spiraling around the trunk, with space between them, so they do not compete or form a cluster at one height. Branches should be smaller than the leader.

Check for hazards first, then remove broken and hanging limbs, make clean cuts at the collar or a lateral, and avoid topping. Rebuild the structure over several years, and keep away from electrical lines.

Remove them when small, cutting suckers at their point of origin and sprouts at the branch or trunk. Heavy pruning and stress stimulate new sprouts, so address the cause as well.

No. Species such as maple, birch, walnut, and elm may drip sap when pruned in late winter or spring. It is unsightly but does not harm the tree, and dormant pruning does not need to be avoided.

Only the loose, torn edges should be removed so the wound has clean margins. Do not enlarge the wound or cut into healthy cambium, and do not shape it into a teardrop.

Central leader (a single dominant trunk), modified central leader, and open center or vase (several main scaffolds with an open middle). The open center admits more light to fruit-bearing branches.

Selective reduction cuts to appropriate laterals over several years, crown cleaning, thinning, or removing the tree and replacing it with a species that fits the site.

Chain saws can make rough cuts, so the final cut must be placed precisely at the collar. Operators need training and PPE, awareness of kickback, and care when cutting above shoulder height.

Large wounds that decay, loss of foliage that starves the tree, many fast-growing weakly attached sprouts, sunscald on newly exposed bark, pest attraction, higher risk, and higher long-term costs.

To reduce risk, improve health and structure, provide clearance, enhance appearance or views, manage size, and encourage flowering or fruiting.

Wide angles of about 45 to 90 degrees from the trunk, with a visible branch bark ridge. Narrow V-shaped angles tend to form included bark and fail.

A cut made flush with the trunk that removes the branch collar and protection zone. It makes a larger wound that closes slowly and allows decay to enter the trunk.

Cutting a branch back to a bud, a stub, or a lateral too small to take over as leader. It stimulates dense, weakly attached sprouts and is generally not recommended for mature trees.

Removal of a branch at its point of attachment or back to a lateral large enough to assume the terminal role. Thinning cuts keep the natural form of the tree and limit stimulation of sprouts.

The industry performance standard for tree pruning. It defines pruning types, cut types, and limits, while ISA Best Management Practices describe how to carry out the work.

Cutting or pinching the new spring shoots (candles) by about half before the needles elongate, to control size and make the crown denser. Cuts into old wood without needles will not regrow.

Cutting stems back to near ground level on a regular cycle to stimulate new shoots from the base. It suits species that sprout vigorously, such as willow and hazel.

Selective removal of dead, dying, diseased, weakly attached, and low-vigor branches from the crown to reduce risk and improve health.

Removal of lower branches to provide clearance for people, vehicles, signs, or buildings. Enough live crown must remain for the tree's health and trunk taper.

Reducing the height or spread of a crown by cutting back to a live lateral at least one-third the diameter of the stem removed. It is used for clearance or to reduce risk when other options are not available, and is not the same as topping.

Pruning to improve the structure and appearance of trees that have been topped, severely pruned, or damaged. It is done over several years by selecting new leaders from sprouts.

Selective removal of branches to increase light penetration and air movement and reduce weight. It should keep a uniform distribution of foliage and the natural form of the tree.

Removing branches at the parent stem or lateral so remaining growth is directed away from the conductors. It follows natural pruning principles and avoids topping the tree.

Another name for a reduction cut: shortening a stem back to a lateral large enough to take over the terminal role, usually at least one-third the diameter of the removed stem.

Shortening a long, heavy branch by cutting back to a lateral to reduce the leverage load on its attachment. It lowers the chance of failure in branches with defects or weak unions.

Training a tree or shrub to grow flat against a wall, fence, or trellis in a formal pattern, by regular pruning and tying of branches.

Stripping the inner and lower lateral branches and leaving foliage tufts at the branch ends. It concentrates weight at the ends, increases breakage, sunscald, and sprouting, and is a harmful practice.

The ratio of the height of the foliage-bearing crown to the total height of the tree. Pruning should maintain enough live crown, generally at least half to two-thirds of the total height, for energy production and trunk taper.

A system of repeated heading back to the same knuckles, begun on young trees and maintained regularly to keep them small. It is not the same as topping a mature tree, which cannot be converted to a pollard.

Pruning of young trees to develop a single dominant leader and well-spaced scaffold branches, correcting defects such as codominant stems and included bark before they become large problems.

The ratio of the branch diameter to the diameter of the trunk or parent stem at the attachment. A small ratio (branch much smaller than the trunk) is well attached, while a ratio near 1 is a weak codominant union.

A reduction cut shortens a stem back to a live lateral at least one-third its diameter, which can take over as leader. A heading cut ends at a bud, stub, or lateral too small to do so.

Bypass pruners cut like scissors, making a clean cut that suits live tissue. Anvil pruners press a blade against a flat surface and tend to crush tissue, which suits dead wood.

Cut back to a live lateral branch or bud. Most pines, spruces, and firs will not regrow from bare wood, so cuts into branches without foliage do not produce new growth.

For branches too heavy to hold: an undercut a foot or so out from the trunk, a top cut a few inches farther out to drop the limb, then a final cut just outside the branch collar to remove the remaining stub.

Indiscriminate cutting of large branches or the trunk back to stubs or small lateral branches, usually to reduce height. It is a harmful practice and not accepted by industry standards.

Selective thinning or removal of branches to open a view through or past a tree, while keeping its natural shape.

Woundwood is the tissue that forms around a wound edge from the cambium. Trees seal wounds by compartmentalizing damaged tissue and growing woundwood over it, and closure rate depends on species, vigor, and wound size.

Keep it clear of all power lines, because even fiberglass poles can conduct electricity when wet or dirty. Only qualified line-clearance workers may work within the minimum approach distance of energized conductors.

The objective, the pruning type (such as clean, thin, raise, or reduce), the size range of branches to be removed, the amount of foliage to be removed, and the clearance required.

For branches up to about 1.5 inches (4 cm) in diameter that are too large for hand pruners, with bypass loppers preferred for live wood so the cut is clean.

Most trees can be pruned at any time. Dormant-season pruning makes the structure easy to see and limits pest activity, while removal of dead, hazardous, or broken branches should be done at any time.

Spring-flowering trees that bloom on old wood should be pruned right after flowering. Summer-flowering trees that bloom on new wood can be pruned in the dormant season.

Just outside the branch bark ridge and the branch collar, without leaving a stub and without cutting into the collar. The collar and protection zone stay on the trunk.

Fresh pruning cuts attract elm bark beetles, which carry Dutch elm disease. Dormant-season pruning avoids the beetle flight period.

Small cuts close faster and expose less wood to decay. Pruning young trees regularly keeps cuts small and avoids large wounds later.

A stub cannot form woundwood to seal the wound, so it dies back and decays, and the decay can spread into the trunk. Cuts should be made at the collar.

Fresh wounds attract sap-feeding beetles that carry the oak wilt fungus. Prune oaks in the dormant season, and treat any unavoidable wounds immediately.

To avoid spreading pathogens such as fire blight, canker diseases, or Dutch elm disease from infected to healthy trees. Common options are 70 percent alcohol or commercial disinfectants, as bleach corrodes tools.

It stops the falling limb from tearing a strip of bark and wood down the trunk, which would create a large wound that is slow to close.

The objectives determine which branches are removed and how much. Without a clear objective, pruning can cause unnecessary wounds, excess foliage loss, and poor structure.

Sharp tools make clean cuts that close faster, while dull tools crush bark and leave ragged wounds. Regular cleaning, lubrication, and sharpening also extend tool life and improve safety.

It sets the limit for branch diameter to be removed, such as all dead branches over 1 inch, so the amount of work and wounds are defined and compliance can be checked.

They damage each other's bark, creating wounds that invite decay, and may create weak structure. Usually the smaller or less well-placed branch is removed.

Mature trees have less capacity to recover from large wounds and foliage loss. Pruning is limited to cleaning and minor corrections, and avoiding large branch removal reduces decay and decline.

No. Dirt, moisture, and carbon content can make them conductive. Only tools and equipment rated and maintained for the voltage should be used, and only by qualified workers.

No. Their insulation is not protective and they can be energized and deadly. Treat them as energized and keep the required distances unless a qualified person determines otherwise.

No. Voltage cannot be judged reliably from appearance, pole size, or insulators. Contact the utility, and if the voltage is unknown assume the highest possible.

They contain layers of ballistic nylon fibers that pull out and clog the sprocket and stop the chain when a moving chain cuts through. They must meet ASTM F1897 and be maintained and replaced after contact.

Wet branches, ropes, and tools conduct electricity much better. Tree parts in contact with lines can energize the whole tree, so wet conditions increase the risk.

Force on the anchor equals twice the rope tension when the rope legs are parallel and decreases as the angle between them widens, reaching the rope tension at 120 degrees.

Apply firm direct pressure and a pressure dressing, use a tourniquet if bleeding cannot be controlled, and call emergency services at once.

By wearing a harness with a lanyard attached to the boom or basket anchorage point, which restricts the worker from being ejected. The lanyard must never be attached to an adjacent pole or tree.

On the ground or otherwise firmly supported, with the chain brake engaged. Drop-starting a chain saw is prohibited.

As energized and dangerous until the utility verifies they are de-energized and grounded. Never assume a line is dead or safe because it is insulated or looks old.

Clear a path at about 45 degrees behind the line of fall, free of obstacles, planned before the cut starts. Move away promptly when the tree starts to move.

Use locking carabiners, keep the gate closed and locked, and load them along the spine. Avoid gate loading, side loading, and cross loading, which can reduce strength greatly.

Feed butt end first from the side of the feed table, never standing in line with the feed path. Avoid loose clothing, never reach into the throat, and use a stick if needed.

To control ascent and descent on a rope and to hold position, using knots such as the Blake's hitch, Distel hitch, or Prusik. They must be dressed correctly and inspected.

The back cut is made opposite the notch and slightly above its base, leaving a strip of uncut wood, the hinge, typically about 10 percent of the diameter thick, which guides the fall.

Hold the saw with both hands and a firm grip, keep a stable stance, cut with the engine at full speed, keep the chain brake in good order, and do not cut above shoulder height unless the work position is secure.

Management commitment, regular training, open communication, proper equipment, clear procedures, and rewarding safe behavior, so everyone feels free to stop an unsafe job.

Call emergency services with the exact location, give first aid within training, secure the scene, and assign someone to meet and guide responders.

Level 1: unqualified for any voltage. Level 2: qualified for 750 V or less. Level 3: qualified up to 35 kV. Level 4 (line clearance): qualified for all voltages. The 2017 'incidental line clearance' category was removed.

A tree caught in another tree may fall without warning. Do not work under it, climb it, or cut the supporting tree; use mechanical means such as a winch or pulling device to bring it down safely.

Inspect before use, set outriggers on firm level ground, stay within load and reach ratings, keep the minimum approach distance from lines, and have a trained ground person for rescue.

A rotating cutter wheel, flying debris, and noise. Operators need eye and face protection, hearing protection, a wheel guard, and bystanders kept clear of the hazard zone.

It must fit correctly, be designed for arborist work, and be used in good condition. It supports the worker and connects to the climbing line or lanyard at attachment points.

Stop the engine and allow it to cool, use an approved container, and refuel at least 10 feet from the location where the saw will be started and away from any ignition sources.

Heavy sweating, headache, nausea, dizziness, and muscle cramps (heat exhaustion), progressing to confusion, hot dry skin, or collapse (heat stroke). Provide shade, water, and rest, and call emergency services for heat stroke.

It adds friction to control the speed of the lowered load, such as a port-a-wrap or rigging ring, reducing the force on the rope and rigging point.

Overhead and underground utilities, traffic, ground conditions, weather, tree defects, nearby people and structures, and access for equipment and rescue.

Overhead and underground utilities, traffic, ground conditions, weather, tree defects, nearby people and structures, and access for equipment and rescue.

Hazards of the job, equipment use, PPE, emergency procedures, and supervised practice before work independently. Training is documented and refreshed regularly.

A written emergency plan, first-aid supplies, trained first-aid and CPR responders, communication methods, and aerial rescue procedures with the ability to carry them out quickly.

A written emergency plan, first-aid supplies, trained first-aid and CPR responders, communication methods, and aerial rescue procedures with the ability to carry them out quickly.

The area where cut limbs or wood may fall or swing. It must be marked, kept clear of people, and communicated to the crew before cutting begins.

A discussion held before work begins to cover the work plan, hazards, protective measures, emergency procedures, and individual roles. It is repeated when conditions or tasks change.

A discussion held before work begins to cover the work plan, hazards, protective measures, emergency procedures, and individual roles. It is repeated when conditions or tasks change.

A qualified arborist trained and authorized to work within the minimum approach distance of energized lines. Line-clearance tree trimming is performed for or on behalf of the utility, within the specified distance of supply lines.

An incident that could have caused injury or damage but did not. Reporting and investigating near misses shows hazards before injuries occur, so corrective action can be taken without blame.

Reaching and lowering an injured climber from a tree. Each crew member should be trained, the plan practiced, and emergency services called first, as speed matters.

The American national safety standard for arboricultural operations. It sets safety requirements for tree work, including equipment, climbing, rigging, electrical hazards, and emergency procedures.

The American national safety standard for arboricultural operations. It sets safety requirements for tree work, including equipment, climbing, rigging, electrical hazards, and emergency procedures.

A sudden upward or backward movement of the guide bar when the chain at the upper tip contacts an object or is pinched. Use the chain brake, low-kickback chain, and avoid cutting with the bar tip.

Hazard communication: labeled containers, safety data sheets (SDS) available to workers, training on the hazards, and proper PPE, storage, and handling.

Using ropes, pulleys, slings, and friction devices to control the movement of cut limbs and wood as they are lowered, reducing impact on the tree, target, and ground.

A sudden force when a falling load is stopped, which can be several times the weight of the piece. It can exceed the WLL of ropes and hardware, so allow slack control and avoid free fall.

Voltage differences across the ground around a contact point or fallen line. A person who steps with feet apart can have current flow through the body, so shuffle with feet together or hop away.

A qualified arborist has training, experience, and demonstrated ability to work with the equipment and hazards. An arborist trainee is learning on the job and works under direct supervision of a qualified arborist.

A qualified arborist has training, experience, and demonstrated ability to work with the equipment and hazards. An arborist trainee is learning on the job and works under direct supervision of a qualified arborist.

Bent stems or limbs hold stored energy and can snap or spring during cutting. Study the load and cut on the compression side first, or release the tension in small steps.

A voluntary consensus standard, but it is widely recognized, and employers can be held to it under OSHA's general duty clause, which requires a workplace free of recognized hazards.

At least 10 feet (3 m) for lines up to 50 kV, adding about 4 inches (10 cm) for each 10 kV above 50 kV. The distance applies to the person, tools, equipment, and the tree parts being cut.

At least 5,400 pounds-force (24 kN) minimum breaking strength. Climbing lines must be inspected before each use and removed from service if damaged.

It directs the fall of the tree. The notch is typically cut one-fifth to one-third of the way through the trunk diameter, with a clean opening aimed at the felling direction.

OSHA enforces workplace safety in the United States. It has no tree-care-specific standard, so it applies general industry rules such as 29 CFR 1910.269 for electrical work and uses ANSI Z133 as a recognized industry standard.

Use a throw bag and throwline or a launcher, keeping clear of power lines and wearing eye protection. Check the line over the tie-in point before climbing.

At least two tree lengths away, with the felling zone clear of people and equipment until the tree is on the ground.

The maximum load a component can safely carry, set by the manufacturer with a safety factor. Never exceed the WLL of any component in the system.

A strong, sound stem or union above the load that can bear the combined forces. The rigging point must be assessed for defects and for the direction of the load.

A strong, sound crotch or stem, high and near the work, where the rope will not rub or pinch. The climber should check it for strength and defects before relying on it.

Shut off the engine, wait for rotating parts to stop completely, and lock out the machine before anyone reaches into the chute or housing.

Hard hat with chin strap when climbing, eye and face protection, hearing protection, chain saw leg protection, proper foot protection, gloves, and high-visibility clothing near traffic.

A feed-control bar or emergency stop within reach, guards over the chute and discharge, a locked chipper housing during operation, and a safe discharge direction away from workers.

The tree's condition from the ground, including defects, dead branches, weak unions, insects, nests, nearby wires, the root zone, and the tie-in point.

Stay in the vehicle and wait for the utility unless there is fire. If forced to exit, jump clear with feet together without touching the vehicle and ground at once, then shuffle or hop away with feet together.

Lean, defects, decay, dead branches, wind, surrounding obstacles, overhead lines, the intended direction of fall, and the escape route.

Keep everyone far away, assume they are energized, and call the utility immediately. Do not touch lines, objects, or trees in contact with them.

Do not touch the person or any equipment in contact. Keep others back, call the utility and emergency services, and let a qualified person remove the hazard before rescue.

ANSI Z87.1. Safety glasses, goggles, or a face shield protect against flying chips, branches, and dust, and a face screen is used with chain saws and chippers.

ANSI Z89.1 covers head protection. A climbing hard hat needs a chin strap that stays on during a fall, and any hat damaged by impact should be replaced.

Signs, cones, flaggers where needed, and placement of vehicles to protect the crew, following the Manual on Uniform Traffic Control Devices. Workers must wear high-visibility clothing.

Sturdy, safety-toed boots with slip-resistant soles, and cut-resistant protection when using a chain saw. Footwear must meet applicable standards such as ASTM F2413.

On trees being removed or in rescue, but not on trees being pruned, because spur holes injure the cambium and bark and can allow decay and pest entry.

When using a chain saw aloft, a second attachment point or work-positioning lanyard should be used, so the climber is secured if the primary system is cut or fails.

When noise reaches about 85 dBA over an 8-hour average. Chain saws, chippers, and stump grinders exceed this, so earplugs or muffs are required.

When working near vehicle traffic or on public roads. ANSI/ISEA 107 garments in the appropriate class make workers visible to drivers.

When it shows cuts, abrasion, chemical or heat damage, or has absorbed a significant fall load. Keep records and inspect all gear before each use.

When lightning is near, strong winds develop, or ice or heavy rain makes climbing or equipment unsafe. Workers should come down from the tree and move to safe shelter.

Low stretch gives better control of loads and reduces bounce and shock loading. Dynamic ropes stretch and are used for fall arrest, not for lowering heavy limbs.

A sharp chain, correct tension, working chain brake, and functioning chain catcher reduce kickback, vibration, and operator fatigue. Inspect before each use.

A standard rope can be cut in a moment by the moving chain. A steel-core, Kevlar, or similar cut-resistant lanyard prevents the climber's lifeline from being severed.

Emergency responders need an address or GPS coordinates, and workers need a working phone or radio. Delays in locating the site or calling for help can cost lives.

Ropes, slings, pulleys, and hardware wear and can fail under load. Inspect before use for cuts, abrasion, heat or chemical damage, and distortion, and remove damaged gear from service.

Lime (calcium carbonate) raises pH, and elemental sulfur lowers it. Lowering pH is difficult in calcareous soils, so selecting adapted species is often the better solution.

Salts lower the soil water potential, so roots have difficulty taking up water, creating drought-like symptoms and leaf scorch. Sodium can also destroy soil structure.

Compaction crushes pore space, reducing oxygen, water infiltration, and drainage, and physically restricting root growth. The result is shallow rooting, decline, and increased susceptibility to stress.

In a layer 2 to 4 inches (5 to 10 cm) deep over as wide an area as practical, kept clear of the trunk and root flare. Piling mulch against the trunk (volcano mulching) promotes decay and pest problems.

Surface broadcast, liquid injection into the soil, subsurface drilling or banding, foliar spray, and trunk injection. Soil applications spread over the root zone are the most common.

Field capacity is the water held in soil after excess has drained by gravity. Permanent wilting point is when water is held so tightly that roots can no longer extract it. Plant-available water lies between the two.

It conserves soil moisture, moderates soil temperature, suppresses weeds, reduces compaction and mower damage, and adds organic matter as it decomposes.

It improves structure, aeration, and water holding capacity, supplies nutrients as it decomposes, increases cation exchange capacity, and feeds soil organisms.

Fine texture that holds large amounts of water and nutrients but drains slowly, has little aeration, warms slowly, and is easily compacted.

Coarse texture with large pores, so it drains quickly and is well aerated, but holds little water and few nutrients.

O (organic layer), A (topsoil with organic matter and most biological activity), B (subsoil where clay and minerals accumulate), C (weathered parent material), and R (bedrock).

Primary: nitrogen (N), phosphorus (P), and potassium (K). Secondary: calcium (Ca), magnesium (Mg), and sulfur (S). Carbon, hydrogen, and oxygen come from air and water.

Iron, manganese, zinc, copper, boron, molybdenum, and chlorine, needed in very small amounts. Deficiencies are often related to pH rather than low total soil content.

Interveinal chlorosis on the youngest leaves, which can progress to leaf scorch and twig dieback in severe cases.

Uniform yellowing (chlorosis) of older leaves first, smaller leaves, sparse foliage, and reduced shoot growth.

Scorching or necrosis along the margins and tips of older leaves, and sometimes a mottled appearance, reduced vigor, and poor stress tolerance.

Sand is the largest (2.0 to 0.05 mm), silt is intermediate (0.05 to 0.002 mm), and clay is the smallest (below 0.002 mm). Soil texture is the relative proportion of the three.

Compacted, low in organic matter, often alkaline, poorly drained, contaminated with debris or salt, and disturbed so that natural horizons are missing.

They are the percentages by weight of nitrogen (N), phosphate (P2O5), and potash (K2O), always in that order. A 20-10-10 fertilizer contains 20 percent N, 10 percent P2O5, and 10 percent K2O.

Generally about 2 to 4 pounds of actual nitrogen per 1000 square feet per year, with lower rates for slow-release sources and stressed trees. Follow label directions and local regulations.

The ability of a soil to hold positively charged nutrients such as calcium, magnesium, potassium, and ammonium. Clay and organic matter have high CEC, and sandy soils have low CEC.

A laboratory test of nutrient concentrations in leaf tissue that shows what the tree has actually absorbed. It is compared with sufficiency ranges for the species and should be sampled at the correct time of year.

A measure of acidity or alkalinity on a scale of 0 to 14, with 7 neutral. Most nutrients are most available at pH 6.0 to 7.0; in acid soils calcium, magnesium, and phosphorus are less available and aluminum and manganese can reach toxic levels.

About 45 percent mineral particles, 5 percent organic matter, 25 percent air, and 25 percent water. The pore space holds air and water for roots.

Infiltration is water entering the soil surface; percolation is water moving downward through the soil profile. A simple drainage test is to fill a hole with water twice, and if water remains after 24 hours, drainage is poor.

Macropores are large spaces that drain freely and hold air. Micropores are small spaces that hold water against gravity and supply it to roots.

Mobile nutrients (nitrogen, phosphorus, potassium, magnesium) move within the tree, so symptoms appear first on older leaves. Immobile nutrients (iron, calcium, zinc) cannot move, so symptoms appear first on new growth.

Quick-release nutrients dissolve at once, giving fast response but a higher risk of burn and leaching. Slow-release products supply nutrients gradually over weeks or months with less risk of burn and loss.

Texture is the proportion of sand, silt, and clay and cannot be changed easily. Structure is how particles are bound into aggregates (peds), and it can be damaged by compaction or improved by organic matter.

Bacteria, fungi, protozoa, nematodes, and earthworms decompose organic matter, cycle nutrients, and improve soil structure. Beneficial fungi such as mycorrhizae also help roots absorb water and nutrients.

Air excavation, vertical mulching (drilled holes backfilled with a porous medium), radial trenching, and organic mulch over a wide area. Care must be taken to avoid cutting or damaging roots.

When roots are active, usually early spring or fall. Heavy nitrogen late in the season in cold climates can stimulate tender growth that is damaged by early frost.

At high pH, iron, manganese, and zinc become less available. Sensitive species show interveinal chlorosis, meaning yellow leaves with green veins.

Water fills the pores and displaces oxygen, so roots cannot respire. Roots die, the tree cannot absorb water, and anaerobic conditions encourage root pathogens such as Phytophthora.

A test shows pH, organic matter, salinity, and nutrient levels, so nutrients are applied only if needed. Many tree problems are not caused by low nutrients, and unnecessary fertilizer can harm trees and the environment.

No. Trees grow in height from the shoot tips, so a branch stays at the same height above the ground even as the trunk thickens and the tree grows taller. Only its diameter increases.

Often two to three times the crown radius or more, well beyond the drip line. Most are shallow, in the upper few feet of soil, which is why the tree is vulnerable to soil disturbance far from the trunk.

Two or more stems of about equal size arising from the same point. They are often weakly attached, especially when included bark is present, and are a common structural defect.

Earlywood forms in spring and has larger, thinner-walled cells. Latewood forms later in the season and has smaller, thicker-walled cells, which appear darker.

Shoots that grow from dormant buds on the trunk or branches, often in response to stress, injury, heavy pruning, or sudden sun exposure. They are usually weakly attached when they arise from older wood.

Small pores in the bark that allow gas exchange (oxygen and carbon dioxide) between the inner living tissues and the atmosphere.

A symbiotic association between fungi and the fine roots of a tree. The fungus extends the absorbing area and improves uptake of water and nutrients, especially phosphorus, while the tree supplies sugars.

Living parenchyma cells arranged radially across the wood. They move water and sugars sideways between xylem and phloem, store energy, and form the basis of CODIT Wall 3.

Short-lived extensions of root epidermal cells that greatly increase surface area for absorbing water and minerals.

Shoots that arise from the roots of a tree, often after root injury or stress. They are weakly attached to the parent root and are usually removed.

Stomata are pores, mostly on the underside of leaves, that allow gas exchange and water vapor loss. Pairs of guard cells open and close them in response to light, water status, and carbon dioxide levels.

Anchoring the tree, transporting water and sugars, and storing energy reserves. The large structural roots near the trunk form the root plate that resists wind loading.

The cuticle and epidermis on the outside, palisade and spongy mesophyll where most photosynthesis occurs, vascular bundles (veins) that carry water and sugars, and stomata that control gas exchange.

Chlorophyll breaks down as the tree prepares for leaf drop, revealing yellow and orange carotenoids that were present all season. Red and purple anthocyanins are newly produced in autumn in some species.

Compartmentalization Of Decay In Trees. Wall 1 resists vertical spread, Wall 2 resists inward spread toward the pith, Wall 3 resists lateral (sideways) spread, and Wall 4 is the barrier zone that protects wood formed after wounding.

A region of actively dividing, undifferentiated cells that produces new tissue. Trees have apical meristems (shoot and root tips) and lateral meristems (vascular cambium and cork cambium).

The suppression of lateral bud growth by hormones, mainly auxin, produced in the terminal bud. Removing the terminal bud releases lateral buds, which is why heading cuts cause dense, vigorous regrowth.

A defense process in which a tree walls off injured or infected tissue to limit the spread of decay and disease. Trees do not heal wounds the way animals do; they seal them off and grow new wood over them.

Reaction wood formed by conifers on the underside (lower side) of leaning stems and branches. It pushes the stem or branch back toward upright.

A seasonal period of reduced metabolic activity triggered by shortening days and cold temperatures. Buds are protected by scales, and many species need a period of chilling before they will break bud in spring.

Bark pinched between two stems or branches in a tight V-shaped union. Because no wood connects the two parts, the union is weak and prone to splitting.

The process in which chloroplasts use light energy to convert carbon dioxide and water into sugars (glucose) and oxygen. It takes place mainly in the leaves.

The process of breaking down sugars to release energy for growth, maintenance, and defense. It occurs in all living cells, day and night.

The gradual decrease in trunk diameter from base to top. Taper develops in response to wind movement, and trees staked too rigidly or grown crowded often lack it and are more likely to bend or fail.

Reaction wood formed by hardwoods (angiosperms) on the upper side of leaning stems and branches. It pulls the stem or branch back toward upright.

The growing region at the tip of each shoot and root. It produces primary growth, which is an increase in length, and is housed in the terminal bud on shoots.

A biomechanics principle that trees add wood where mechanical stress is highest, so stress is spread evenly over the surface. This adaptive growth explains features such as taper and root flare.

A raised ridge of bark in the crotch where a branch joins a trunk or larger branch. It marks the upper limit of the attachment and guides the angle of a proper pruning cut.

The swollen area at the base of a branch formed by overlapping branch and trunk tissues. It contains the branch protection zone, so a proper pruning cut is made just outside the collar.

A chemically protected area at the base of a branch, within the collar and branch bark ridge, that helps resist the spread of decay into the trunk. Cutting flush or leaving a long stub damages or fails to use this protection.

Water is pulled upward through the xylem by tension created by transpiration. Cohesion between water molecules and adhesion to xylem walls keep the water column continuous.

A lateral meristem that produces cork cells to the outside, forming the protective outer bark (periderm). It is a different tissue from the vascular cambium.

Dormant (latent) buds formed earlier and stayed inactive until stimulated. Adventitious buds form from tissue where no bud existed before, such as callus or cambium after wounding.

Excurrent form has a single dominant central leader with smaller lateral branches, giving a conical shape (spruce, sweetgum). Decurrent form has lateral branches that outgrow the leader, giving a spreading, rounded crown (elm, oak).

Gymnosperms (conifers, ginkgo, cycads) bear naked seeds, usually in cones, and have only tracheids in their xylem. Angiosperms bear flowers and enclosed seeds in fruits and have vessels in their xylem.

Inner bark is the living phloem that carries sugars. Outer bark is dead cork tissue that protects the tree from water loss, temperature extremes, pests, and mechanical injury.

Primary growth is an increase in length from the apical meristems. Secondary growth is an increase in girth from the vascular cambium and cork cambium.

Ring-porous woods (oak, ash, elm) have large vessels concentrated in the earlywood. Diffuse-porous woods (maple, birch, poplar) have vessels of similar size spread evenly across the ring.

Sapwood is the outer, living and functioning xylem that conducts water and stores energy. Heartwood is the inner, nonconducting xylem that no longer holds living cells and mainly gives structural support.

Phloem transports sugars (photosynthates) made in leaves to areas that use or store them, such as roots, buds, and growing tips. It makes up the inner bark.

Xylem conducts water and dissolved minerals upward from the roots to the leaves. It also gives structural support and, in sapwood, stores some carbohydrates.

ABA is a stress-related hormone. It causes stomata to close during water stress and promotes bud dormancy.

Auxin is produced in shoot tips and young leaves. It promotes cell elongation, maintains apical dominance, and stimulates root initiation. It moves downward through the tree.

Cytokinins are produced mainly in root tips and move upward. They promote cell division, counter apical dominance, and delay leaf senescence.

Ethylene is a gaseous hormone involved in fruit ripening, leaf and fruit drop (abscission), and the response to wounding and other stress.

Gibberellins promote stem elongation, seed germination, and flowering. They work together with other hormones to regulate growth.

The transition zone where the trunk widens into the major roots. It should be visible at or just above grade; planting or mulching too deep can bury it and lead to stress and decay.

A thin layer of dividing cells between the xylem and phloem. It produces new xylem to the inside and new phloem to the outside, increasing the diameter of stems and roots (secondary growth).

The loss of water vapor from the leaves, mostly through the stomata. It cools the leaf and creates the pull that moves water up through the xylem.

In the upper 12 inches (30 cm) of soil, where oxygen, water, and nutrients are most available. These small roots are the main sites of water and nutrient uptake.

As starch and other carbohydrates in living parenchyma cells of the roots, trunk, and branches, especially in the sapwood and roots. These reserves fuel spring growth, defense, and wound response.

Wall 1 (resisting up and down spread) is the weakest. Wall 4, the barrier zone formed by the cambium after wounding, is the strongest.

Because the outer sapwood and the cambium do the conducting and growing, not the heartwood. Survival is possible, but the loss of wood reduces mechanical strength and can raise the risk of failure.

Reserves fund growth, defense, and recovery. A tree with low reserves grows less, compartmentalizes wounds poorly, and becomes more vulnerable to pests, pathogens, and further stress.

Monocots have no vascular cambium, so their trunks do not add annual rings or increase in girth over time. Their vascular bundles are scattered through the stem rather than arranged in rings.

No. Hardwood refers to broadleaf angiosperms and softwood to conifers (gymnosperms). Some hardwoods such as basswood are softer than some softwoods.

Choose cultivars bred or selected for resistance, such as disease-resistant elms for Dutch elm disease or scab-resistant crabapples.

Pines bear needles in bundles called fascicles. Eastern white pine has 5 needles per fascicle, red and Scots pine have 2, and loblolly and ponderosa pine usually have 3.

Spruce needles are four-sided, stiff, sharp, and roll between the fingers, attached on small pegs. Fir needles are flat, soft, and attach directly to the twig. Hemlock needles are short, flat, and attached by a tiny stalk.

A bud sits at the base of the petiole of a true leaf, but there is no bud at the base of individual leaflets. A compound leaf has several leaflets sharing one petiole with a single bud at its base.

A cultivar is a cultivated variety selected and propagated for specific traits. It is capitalized and set in single quotes, not italicized, such as Acer rubrum 'October Glory'.

With a multiplication sign (x) before the species epithet for a cross between two species, such as Platanus x acerifolia (London planetree).

Columnar, pyramidal, oval, round, spreading, vase-shaped, and weeping. Crown form guides use in screening, shade, and space-limited sites.

Entire (smooth), serrate (toothed), doubly serrate, dentate, and lobed. The margin is a major identification feature.

Kingdom, phylum (division), class, order, family, genus, and species, from the broadest group to the most specific.

Pinnate (one main vein with side veins), palmate (several main veins from the base), and parallel (veins run side by side, as in monocots).

Alternate (one leaf per node), opposite (two leaves per node, across from each other), and whorled (three or more leaves per node).

Rings of scars left where the terminal bud scales fell. The distance between successive scars marks one year of twig growth, so they can be used to judge growth rate and twig age.

The abbreviation sp. refers to a single unspecified species of a genus, and spp. refers to several species of that genus.

Common trees with opposite branching and leaf arrangement: Maple, Ash, Dogwood, and Horsechestnut (or buckeye).

Selecting a species whose mature size, form, and site requirements match the planting location, including light, soil, moisture, space, hardiness, and nearby structures or utilities.

Plant family names end in -aceae, such as Fagaceae (oaks and beeches) and Rosaceae (roses, apples, and cherries).

Sweetgum bears a spiny, woody capsule ball. American sycamore bears a round ball of tightly packed seeds hanging on a long stalk.

A leaf whose leaflets are themselves divided into smaller leaflets, such as in honeylocust and Kentucky coffeetree.

An identification tool that offers paired contrasting choices at each step, leading the user step by step to the correct plant name.

A dry, winged fruit that does not split open. Maples, ash, and elms produce samaras.

The scientific naming system using two names: the genus (capitalized) and the species epithet (lowercase), both italicized or underlined, such as Quercus alba.

No more than 10 percent of the trees should be one species, 20 percent one genus, and 30 percent one family.

A botanical variety (var.) is a naturally occurring variant within a species and is written in italics. A cultivar is a human-selected plant maintained through propagation.

A drupe is a fleshy fruit with a single hard stone around the seed (cherry, plum). A pome has a fleshy outer layer around a papery core with seeds (apple, pear, crabapple, hawthorn).

Monoecious trees bear male and female flowers on the same tree (oak, birch). Dioecious trees bear them on separate trees (ginkgo, holly, many poplars), so only female trees produce fruit.

Native trees evolved in the region. Non-native trees were introduced from elsewhere. Invasive trees spread aggressively and harm natural areas or ecosystems; not all non-native trees are invasive.

Pinnately compound leaflets are arranged along a central rachis (ash, hickory, walnut). Palmately compound leaflets radiate from a single point at the end of the petiole (buckeye, horsechestnut).

The average annual extreme minimum winter temperature, divided into zones of 10 degrees Fahrenheit, each split into a and b half zones of 5 degrees.

Messy fruit or litter, thorns, heavy seed or pollen, brittle wood, aggressive roots, and sap drip, as these affect safety, maintenance, and client satisfaction.

Sun exposure, soil texture, pH, drainage, compaction, available rooting space, overhead and underground utilities, hardscape, wind, de-icing salt, and irrigation availability.

A low-growing species with a mature height well below the wires, so that utility pruning and conflicts are avoided in the future.

Evergreens suit year-round screens and winter windbreaks. Deciduous trees provide summer shade and allow winter sun, which helps passive heating of buildings.

Tolerance to compaction, drought, heat, restricted rooting volume, poor drainage, pollution, and de-icing salt. Examples often used include honeylocust, ginkgo, and London planetree.

Bald cypress, dawn redwood, and larch (tamarack) drop their needles in autumn, unlike most evergreen conifers.

Species tolerant of periodic flooding, such as bald cypress, river birch, swamp white oak, and red maple.

Female ginkgo trees produce fleshy seeds with an unpleasant odor when they fall, so fruitless male cultivars are preferred for streets and landscapes.

Common names vary by region and may refer to several different species, while a scientific name is unique and recognized worldwide.

Local conditions such as heat from pavement, building walls, wind exposure, or frost pockets can differ greatly from the regional hardiness zone and affect survival and performance.

High soil pH reduces availability of iron and manganese, causing yellow leaves with green veins. Species adapted to acid soils, such as pin oak, are especially prone.

Identification determines a tree's growth habit, site needs, pest and disease susceptibility, response to pruning, structural tendencies, and risk. It also allows clear communication with clients and other professionals.

Roots need enough uncompacted, aerated soil for water, nutrients, and anchorage. Limited soil volume restricts tree size, vigor, and lifespan, so large-maturing species should not be planted in small pits.

Its narrow branch angles and included bark cause frequent limb splitting, and Callery pear seedlings and hybrids have become invasive in many regions.

A diverse population limits the damage from any one pest or disease, such as emerald ash borer or Dutch elm disease, which can destroy a heavily planted species.

Bark changes with age, site, and growth rate, so young trees may look quite different from mature ones. It is best used together with leaves, buds, twigs, fruit, and form.

No. Risk can be reduced but not eliminated, because trees are living organisms and can fail in extreme weather even when they appear sound.

No. Risk can be reduced but not eliminated, because trees are living organisms and can fail in extreme weather even when they appear sound.

A mallet is tapped on the trunk to detect hollow or dull sounds that suggest decay, and a thin probe measures the depth of cavities and cracks.

A mallet is tapped on the trunk to detect hollow or dull sounds that suggest decay, and a thin probe measures the depth of cavities and cracks.

By their location, length, orientation, and whether there is movement. Cracks along the grain at branch unions or across the trunk can signal impending failure.

By their location, length, orientation, and whether there is movement. Cracks along the grain at branch unions or across the trunk can signal impending failure.

By relocating or restricting access to the target zone, with fencing, signs, moving parking or seating, or rerouting paths.

By relocating or restricting access to the target zone, with fencing, signs, moving parking or seating, or rerouting paths.

Risk rises as the sound wall gets thinner. A common guide is that the wall thickness (t) divided by the trunk radius (R) below about 0.3 raises concern, but it is not a hard rule and must be judged with other factors.

Risk rises as the sound wall gets thinner. A common guide is that the wall thickness (t) divided by the trunk radius (R) below about 0.3 raises concern, but it is not a hard rule and must be judged with other factors.

By the size of the dead branches, their height above the target, and the likelihood of impact. Large dead branches over high-use areas are given priority for removal.

By the size of the dead branches, their height above the target, and the likelihood of impact. Large dead branches over high-use areas are given priority for removal.

The combination of the likelihood of a failure occurring, the likelihood that it will strike a target, and the consequences if it does. Risk is rated using a matrix.

The second matrix combines the likelihood of failure and impact with the consequences (negligible, minor, significant, severe) to give a risk rating of low, moderate, high, or extreme.

It combines the likelihood of failure (improbable, possible, probable, imminent) with the likelihood of impact (very low, low, medium, high) to give the overall likelihood of failure and impact: unlikely, somewhat likely, likely, or very likely.

Often estimated as the area within one to one and a half times the tree's height. Branch failures affect a smaller zone, and sloping ground may extend the zone.

Often estimated as the area within one to one and a half times the tree's height. Branch failures affect a smaller zone, and sloping ground may extend the zone.

In clear, plain language, preferably in writing, with the rating, the reasons, the options available, the likely outcomes of each, and any limitations of the assessment.

Start with a safety check of the site, then look for hangers, cracks, split unions, root plate movement, and leaning trees, addressing the most hazardous situations first.

Start with a safety check of the site, then look for hangers, cracks, split unions, root plate movement, and leaning trees, addressing the most hazardous situations first.

Broken branches lodged in the crown, hanging by bark or caught on other limbs. They can fall without warning and should be removed promptly.

Broken branches lodged in the crown, hanging by bark or caught on other limbs. They can fall without warning and should be removed promptly.

Cables and braces installed to reduce the risk of failure in weak unions or defective stems, covered by ANSI A300 Part 3. They require regular inspection and do not eliminate risk.

Cables and braces installed to reduce the risk of failure in weak unions or defective stems, covered by ANSI A300 Part 3. They require regular inspection and do not eliminate risk.

Pruning, support systems (cabling and bracing), removal of the tree, relocating or protecting the target, restricting access, and modifying the site or tree environment.

Negligible, minor, significant, and severe. They are based on the harm or damage if the target is struck, including the value of property and the likelihood of injury.

Improbable (unlikely to fail), possible (could fail but not likely), probable (expected to fail), and imminent (failure has started or is about to occur). They are rated for a defined time period.

Very low, low, medium, and high. They depend on whether the failing part would strike the target and on how often the target is present in the target zone.

Wind, snow and ice, rain, and the tree's own weight. Wind is usually the most important, and crown density and leaf-on conditions change the load.

Wind, snow and ice, rain, and the tree's own weight. Wind is usually the most important, and crown density and leaf-on conditions change the load.

ANSI A300 Part 9 (the tree risk assessment standard), the ISA Best Management Practices for Tree Risk Assessment, and the ISA Tree Risk Assessment Qualification (TRAQ).

Constant, frequent, occasional, and rare. They describe how often a target such as a person or vehicle is present in the target zone.

Constant, frequent, occasional, and rare. They describe how often a target such as a person or vehicle is present in the target zone.

Level 1 (limited visual), Level 2 (basic), and Level 3 (advanced). The level is chosen based on the client's needs, the tree, and the site.

Branches, the trunk, and the roots. Each fails in a different way, and the part that fails determines the size of the failure and the targets that could be hit.

Fruiting bodies of wood decay fungi, showing that decay is present inside. The type of fungus and the extent of decay determine how serious the defect is.

Fruiting bodies of wood decay fungi, showing that decay is present inside. The type of fungus and the extent of decay determine how serious the defect is.

A recent lean with raised soil on one side and cracked soil on the other suggests root plate failure is underway. A long-standing lean with corrective growth is often less of a concern.

A recent lean with raised soil on one side and cracked soil on the other suggests root plate failure is underway. A long-standing lean with corrective growth is often less of a concern.

Poor vigor and possible root or vascular problems. Dying parts also become brittle and more likely to fail.

Poor vigor and possible root or vascular problems. Dying parts also become brittle and more likely to fail.

A detailed inspection of the tree and its surroundings from all sides, including the trunk base and crown, using simple tools such as a mallet and probe, with the tree history and site noted.

A quick visual check from a specified perspective, such as a walk-by or drive-by, to look for obvious defects on many trees. It is useful for screening large populations.

A program that surveys tree populations on a schedule, with high-use areas and high-risk species inspected more often, so resources go where the risk is greatest.

A program that surveys tree populations on a schedule, with high-use areas and high-risk species inspected more often, so resources go where the risk is greatest.

The typical way and place in which a species tends to fail, such as limb breakage, trunk snap, or root failure. It helps the assessor focus on likely weaknesses.

The typical way and place in which a species tends to fail, such as limb breakage, trunk snap, or root failure. It helps the assessor focus on likely weaknesses.

People, property, or activities that could be injured or damaged by tree failure. Targets are assessed by occupancy rate and by whether they can be moved or protected.

A static load test that pulls on the tree with a controlled force and measures the response to estimate stability and resistance to wind or root failure.

A static load test that pulls on the tree with a controlled force and measures the response to estimate stability and resistance to wind or root failure.

Use of specialized tools and techniques, such as resistance drilling, sonic tomography, or a load test, when a basic assessment leaves unanswered questions.

To extract a thin core from a trunk to examine wood condition and growth rate. It wounds the tree, so it is used carefully and generally not through decayed wood.

To extract a thin core from a trunk to examine wood condition and growth rate. It wounds the tree, so it is used carefully and generally not through decayed wood.

The risk that remains after mitigation has been carried out. It should be assessed and reported so the owner knows what level of risk remains.

A thin needle is drilled into the wood and the resistance recorded, which shows voids and decay. It is minimally invasive and used in advanced assessments.

A thin needle is drilled into the wood and the resistance recorded, which shows voids and decay. It is minimally invasive and used in advanced assessments.

A noninvasive technique that measures the speed of sound waves across the trunk to create a map of decayed or hollow areas.

A noninvasive technique that measures the speed of sound waves across the trunk to create a map of decayed or hollow areas.

A hazard is a tree or defect that could cause harm. Risk is the estimated probability and severity of that harm, so a defective tree with no target poses little risk.

Owners are expected to take reasonable steps to inspect and manage trees, and assessors to work within their qualifications. Recommendations and decisions should be documented.

Owners are expected to take reasonable steps to inspect and manage trees, and assessors to work within their qualifications. Recommendations and decisions should be documented.

Severed or decayed roots, girdling roots, heaving soil, an uplifted root plate, and root loss from construction or grade changes.

Severed or decayed roots, girdling roots, heaving soil, an uplifted root plate, and root loss from construction or grade changes.

The assessor, date, tree location and species, assessment level and limitations, defects found, targets, likelihood and consequence ratings, risk rating, and mitigation options with residual risk.

Wind exposure, topography, soil conditions, recent site changes such as construction or grade change, drainage, and nearby trees or structures.

Wind exposure, topography, soil conditions, recent site changes such as construction or grade change, drainage, and nearby trees or structures.

Species and failure profile, age, vigor, tree health, structure and defects, size, crown density, and pruning history.

Species and failure profile, age, vigor, tree health, structure and defects, size, crown density, and pruning history.

Bulges, seams, cankers, deep cavities, large wounds, and swellings that indicate hidden decay or structural weakness.

Bulges, seams, cankers, deep cavities, large wounds, and swellings that indicate hidden decay or structural weakness.

When risk cannot be reduced to an acceptable level by other means, taking into account the tree's value and benefits and the cost of the alternatives.

When risk cannot be reduced to an acceptable level by other means, taking into account the tree's value and benefits and the cost of the alternatives.

At the interval stated in the report, and after storms, construction, changes in the site, or new symptoms, because defects and conditions change over time.

At the interval stated in the report, and after storms, construction, changes in the site, or new symptoms, because defects and conditions change over time.

The tree owner or manager decides the acceptable level of risk and whether to mitigate, the risk assessor provides information and recommendations, and regulators or the public may set requirements.

The tree owner or manager, based on the information provided by the risk assessor, their policies and risk tolerance, and applicable laws.

Their weight and leverage at the end load the attachment point, which can fail. Reducing end weight can lower the risk.

Their weight and leverage at the end load the attachment point, which can fail. Reducing end weight can lower the risk.

Regrowth from stubs is weakly attached and often arises from decayed wood, so the new branches are prone to failure, especially as they get larger.

Regrowth from stubs is weakly attached and often arises from decayed wood, so the new branches are prone to failure, especially as they get larger.

Dead ash wood becomes brittle quickly and can fail unpredictably, so large dead ash trees near targets should be removed promptly and with care.

Dead ash wood becomes brittle quickly and can fail unpredictably, so large dead ash trees near targets should be removed promptly and with care.

Records and photos show the condition at the time of assessment, support recommendations, and provide evidence if the client or others question the decision later.

Records and photos show the condition at the time of assessment, support recommendations, and provide evidence if the client or others question the decision later.

It forms a weak union with no wood connection, so the stems can split apart, particularly when the stems are large and codominant.

It forms a weak union with no wood connection, so the stems can split apart, particularly when the stems are large and codominant.

To examine the upper crown and branch unions that cannot be seen well from the ground, using climbing techniques, binoculars, or a drone.

To examine the upper crown and branch unions that cannot be seen well from the ground, using climbing techniques, binoculars, or a drone.

Risk changes over time, so the rating applies to a defined period, commonly one year, after which the tree should be reassessed.

Use no-dig construction: lay geotextile and a coarse, load-bearing base above grade instead of excavating, or bridge the roots with a suspended structure.

Keep traffic out of the protection zone. If it cannot be avoided, spread at least 6 inches of wood chip mulch and cover it with plywood or steel plates to distribute the load.

Changes in grade, drainage, or irrigation can flood or dry the root zone, and nearby excavation and dewatering can lower the water table that trees rely on.

Through contract specifications, regular inspections by the project arborist, and penalties for damage, often based on the appraised value of the tree.

Prune ahead for clearance and, where fencing is not possible, wrap the trunk with padding and strap boards around it. This reduces bark wounds from machinery.

By boring or tunneling beneath the roots, typically at least 2 feet (60 cm) deep and beyond the trunk area, rather than cutting an open trench.

By compacting soil, cutting roots, changing grade, burying or stripping soil, contaminating the soil, injuring trunks and branches with equipment, and altering drainage and water supply.

Young, vigorous trees recover better from root loss. Mature and over-mature trees have less capacity to regrow roots and are more affected by changes in the site.

Fill over the root zone reduces oxygen and gas exchange to roots and can smother them. Even a few inches can harm sensitive species, and deeper fill can kill roots and lead to decline.

Through concrete washout, spilled fuel and oil, paint and solvents, and lime leachate that raises pH. Such substances are kept out of the root zone.

It removes topsoil and many of the absorbing roots, may expose or cut structural roots, and lowers the tree's stability and water access.

Tolerance varies widely. Sensitive species often include American beech, birches, and many conifers such as pine and spruce, while some adaptable species tolerate more disturbance.

By species tolerance to construction, health, age, structural condition, and location. Healthy, tolerant, and well-placed trees are good candidates for preservation, while poor trees may be better removed.

Cut them cleanly behind the damage with sharp tools and keep the roots moist and covered with soil or mulch to prevent drying.

Trim loose torn bark edges to clean margins, avoid wound dressing, and monitor the wound. Do not enlarge it.

Generally no. Compensatory pruning reduces the leaf area that makes energy for recovery. Prune only dead, broken, or hazardous branches.

Only if a soil or foliar test shows a deficiency. Heavy nitrogen forces shoot growth that the damaged root system cannot support.

Thinning crowns, small or scorched leaves, branch dieback, early fall color, leaning, and reduced growth, followed by secondary pests and decay.

Sturdy fencing, often chain link at least 6 feet tall, installed at the edge of the protection zone before work begins, marked with signs, and left in place until construction is complete.

Use reduced protection zones with thick mulch, plywood or steel plates over the roots, and padded trunk guards, and limit access to short periods under arborist supervision.

The standard for management of trees and shrubs during site planning, site development, and construction. It covers assessment, protection, and maintenance practices for trees on development sites.

A document that identifies the trees to be saved, sets protection zones and measures, and defines construction practices, monitoring, and penalties. It is prepared before work starts and followed by all contractors.

Using compressed air to remove soil from around roots without cutting them. It lets crews expose roots for inspection, utility installation, or root pruning.

Each tree's species, trunk diameter, condition, structure, and location, plus its suitability for preservation. This allows the plan to focus on the trees worth saving.

A paving surface such as porous asphalt, pavers with open joints, or gravel that allows air and water to pass into the soil, reducing harm to roots beneath the pavement.

Treatments before work begins, such as pruning deadwood, mulching, watering, and root pruning, to increase the tree's capacity to withstand stress.

Cutting roots cleanly along the edge of the protection zone before excavation begins, ideally weeks or months ahead, so roots can regrow and the tree is not torn by machinery.

Improving the soil around damaged roots by loosening compaction, adding organic mulch, aerating, and correcting drainage so new roots can grow.

Assess the damage to roots, trunk, and crown and identify hazards, then begin remedial care such as watering, mulching, and monitoring.

Tree wells do not solve the loss of roots, because most roots lie outside the well. Retaining walls and aeration systems may help, but only if they are placed far enough from the trunk.

Trees left standing after neighbors are removed are exposed to stronger wind and may blow over, especially if roots were cut. Thin gradually and assess edge trees carefully.

To assess trees, write and review specifications, supervise root pruning and work within protection zones, monitor compliance, and recommend treatments if damage occurs.

The area closest to the trunk containing the large roots that anchor the tree. Cutting roots here compromises stability, so excavation in the SRZ should be avoided.

The area around a tree that is kept free of construction activity. A common guide is 1 foot (30 cm) of radius for each inch (2.5 cm) of trunk diameter, increased for sensitive or older trees.

A site plan with tree locations, protection zones and fence lines, access and haul routes, staging areas, utility routes, protection and mitigation measures, and monitoring and penalty provisions.

When the tree is small, healthy, and valuable enough to justify moving, but cannot be protected in its original location by any reasonable design change.

Outside the tree protection zones, in designated staging areas, with no dumping or storage of materials, fuel, or debris on the root zone.

They keep heavy equipment out of protection zones, and routes outside the root zones prevent compaction and root damage over the whole project.

Photos, inspection logs, and meeting notes show that protection measures were installed and kept in place, and they help defend decisions if disputes or claims arise.

Piers can be placed between major roots, which avoids the continuous excavation of a footing and reduces root cutting.

They are suddenly exposed to wind, sun, and temperature extremes they did not develop under, which can cause sunscald, windthrow, and decline.

Root loss reduces water uptake, so the tree needs regular deep watering through the next growing seasons until roots regrow.

Trenching severs roots, which reduces water and nutrient uptake and can weaken anchorage. Roots cut near the trunk are the most damaging, and large roots should not be cut at all if possible.

Trees have stored reserves, so symptoms of root loss and stress often appear two to ten years or more after the work.

Root loss, grade changes, and exposure can reduce stability, so a tree that was sound before may become hazardous near people and structures.

Trees that shade the west and east walls in summer reduce cooling needs, evergreen windbreaks reduce winter heating loss, and deciduous trees on the south side allow winter sun.

Species should tolerate expected heat, drought, and new pests, and a diverse mix of well-adapted trees helps the urban forest stay resilient.

Crowns intercept rainfall, roots take up water, and root channels help water infiltrate the soil, reducing runoff, erosion, and flooding.

Leaves capture particulates and absorb gases such as ozone and nitrogen dioxide. Shade also reduces the formation of ground-level ozone.

Shade blocks sunlight from heating pavement and buildings, and transpiration cools the air. Trees can lower surface and air temperatures significantly.

Listen, document the concern, explain the reasons and the options, stay professional, and refer disputes to the tree board or proper authority when needed.

Damage or loss claims, insurance, ordinance penalties and mitigation, tax deductions, litigation, and development planning.

Use plain language, explain the reasons and benefits, notify neighbors in advance, and respond to questions consistently and respectfully, with visuals when possible.

A vision and goals, resource assessment and inventory, strategies and actions, implementation schedule and budget, and monitoring and evaluation, so the plan adapts over time.

Higher property values, lower energy and stormwater costs, longer pavement life, and increased customer traffic in shopping areas.

Maintain a tree board or department, have a community tree ordinance, spend at least 2 dollars per capita on urban forestry, and hold an Arbor Day observance and proclamation.

Environmental (shade, stormwater, air quality, wildlife), economic (energy savings, property value), and social (health, community, and aesthetic benefits).

Reduced stress, more outdoor activity, stronger community ties, and better mental and physical health, along with cleaner and cooler neighborhoods.

Cost approach, sales comparison approach, and income capitalization approach. The cost approach is the most commonly used for trees.

They protect large, old, or especially valuable trees by requiring permits, protection during development, and mitigation or replacement if removal is allowed.

Species rating (how well the species suits the area), condition (health and structure), and location (site, contribution, and placement).

A record of the trees in a community, including species, size, condition, location, and maintenance needs. It may be a complete inventory or a sample, and supports planning and budgeting.

A local law that sets standards for planting, care, protection, and removal of trees, assigns responsibility, and sets permits and penalties. It gives a community legal authority to manage its trees.

A free suite of software tools from the USDA Forest Service and partners, such as i-Tree Eco and i-Tree Canopy, that measure the structure, benefits, and value of urban forests.

A method for trees small enough to be replaced from nursery stock. Value is the cost of a similar tree plus installation and establishment, adjusted for condition.

Trees take up carbon dioxide and store carbon in wood and roots. Large, long-lived, healthy trees store the most.

A method for trees too large to replace that estimates value using the cost of a nursery tree adjusted for trunk area, species, condition, and location ratings.

An estimate of the monetary value of a tree. The Guide for Plant Appraisal, published by the Council of Tree and Landscape Appraisers, is the standard reference in North America.

The percentage of the ground covered by tree crowns when viewed from above. Communities set canopy goals and track progress with aerial imagery or tools such as i-Tree Canopy.

The management of trees and related resources in and around communities, to provide environmental, economic, and social benefits to the people who live there.

Usually the municipality, as they are in the public right-of-way, although ordinances may assign some duties to adjacent owners. Planting lists and spacing rules reduce conflicts with sidewalks and utilities.

Laws such as the Migratory Bird Treaty Act protect active nests, and many places restrict removal during nesting season. Surveys before work avoid harming wildlife and legal problems.

A mix of young, semi-mature, and mature trees ensures continuity of canopy and spreads costs and risks. A population all of one age can decline or require replacement all at once.

Public involvement builds support, volunteers, and stewardship through planting events, Arbor Day activities, and citizen participation in planning.

Areas with low canopy often suffer more heat and pollution and have fewer resources. Canopy and heat maps help direct planting where the benefits are greatest.