Arborist glossary

The terms cover pruning, removal, crane work, stumps and roots, fire and land clearing, Lake Tahoe permits, and firewood. If a word on your estimate is not here, ask the arborist. Every estimate should be easy to understand.

Terms, A to Z

0-9

811

The national call-before-you-dig number. Underground utilities are marked before any digging, which includes grinding a stump below grade.

A

Alkaline soil

Alkaline soil is soil with a pH above 7. Much of the soil in the arid West is alkaline, and a high pH can lock up iron and other nutrients so that some trees turn yellow even when the nutrients are present in the ground.

ANSI A300

The American National Standards for tree care work, including pruning. It is the standard the industry follows, and it does not accept topping as pruning.

ANSI Z133

The American National Standard for safety in tree work, covering climbing, rigging, aerial lifts, chippers and work near power lines.

Apical dominance

Apical dominance is a tree's tendency to put growth into its topmost shoot, and to suppress the buds and shoots below it, through hormones made in the growing tip. It is why a young pine grows up in a single leader with side branches spaced around it.

Arborist

A person trained in the care of individual trees. An ISA Certified Arborist has passed the International Society of Arboriculture's exam and keeps the credential current with continuing education.

B

Blue stain fungus

Blue stain fungus is a group of fungi carried into a tree by bark beetles that stain the sapwood gray, blue or blackish. When an arborist sees the stain in a cut pine, it is strong evidence that beetles attacked the tree before it died.

Boom truck

A truck with an extending boom and a bucket that lifts an arborist into the crown. Also called a bucket truck or aerial lift. Ours is a 75-foot Altec GMC.

Branch bark ridge

The branch bark ridge is the raised, rough line of bark that runs along the upper side of the angle where a branch meets the trunk or a larger limb. It is the place where the two sets of bark are pushed together as they grow.

Branch collar

The slightly swollen ring where a branch joins the trunk. A correct pruning cut is made just outside it so the wound can close.

Brush mowing

Cutting brush and tall weeds with a heavy mower, often for fire fuel reduction on open lots.

Buttress roots

Buttress roots are large, thick roots that swell out from the base of a trunk and run along the ground, giving the tree extra support on the side where the load is greatest. They are part of the root flare.

C

Cabling and bracing

Installing cables or rods in a tree to support weak unions or heavy limbs.

Caliche

Caliche is a hard, whitish layer of soil cemented with calcium carbonate, found in dry climates where there is too little rain to wash minerals out. It can be a few inches to many feet thick, and roots and water cannot pass through it easily.

Cambium

The cambium is a thin layer of actively dividing cells between the bark and the wood. Each growing season it adds new wood inward and new bark outward, which is how a trunk gets thicker.

Canker

A canker is a localized area of dead bark and the tissue beneath it on a trunk or branch, often sunken, cracked or swollen at the edges. Cankers can come from fungi, bacteria, sun, cold or mechanical injury, and the size of the canker against the size of the limb decides how serious it is.

Canopy

The combined crowns of the trees over a yard, street or lot. Also used for the leafy part of a single tree.

Cavity

A hollow in a trunk or limb where decayed wood has gone.

Chipper

The machine that turns limbs and brush into wood chips, usually towed behind the chip truck.

Climber

The crew member who works in the tree on ropes and a harness, making the cuts and attaching the crane or the rigging.

Climbing spurs

Climbing spurs, also called gaffs or hooks, are pointed steel spikes attached to a climber's boots that bite into the trunk. They wound the bark and cambium, so they are generally kept for trees that are coming down, apart from specific rescue or work situations.

CODIT (compartmentalization of decay in trees)

CODIT stands for compartmentalization of decay in trees. It is a model, developed by tree biologist Alex Shigo, of how a tree walls off damaged and decayed wood so that the rot stays in one place and the tree keeps growing.

Codominant stems

Two or more trunks of about the same size growing from one fork. The union between them is often weak.

Conifer

A cone-bearing tree, usually evergreen with needles or scales, such as a pine, fir, spruce, cedar or juniper.

Conk

The shelf-like fruiting body of a wood decay fungus on a trunk or at the base of a tree. It is a sign of decay inside.

Cord

The standard measure of firewood: 128 cubic feet of stacked wood, such as a stack 4 feet high, 4 feet deep and 8 feet long. See how big a cord is.

Crane pick

A crane pick is one lift of a crane: the cut piece of tree is attached to the hook, the crane takes its weight, and the operator lifts it clear and sets it in the drop zone. A tree removal by crane is a series of picks, one for each section.

Crane-assisted removal

Removing a tree in sections that a crane lifts up and away to a drop zone, instead of lowering each piece on ropes. See how we do it.

Critical root zone

The critical root zone, or CRZ, is the area of ground around a tree that holds enough roots to keep it alive and stable. Digging, grading, paving or parking inside it can harm or kill the tree, so arborists mark it off before construction.

Crown

The branches and foliage of a tree, above the trunk.

Crown cleaning

Pruning out dead, dying, broken and rubbing branches without changing the size or shape of the tree.

Crown fire

A crown fire is a wildfire that burns in the crowns of trees, moving from treetop to treetop rather than along the ground. It spreads faster, throws more embers and is far harder to fight than a fire on the surface.

Crown raising

Removing the lowest branches for clearance over a roof, driveway, walk or street. Also called limbing up.

Crown reduction

Shortening a tree's height or spread by cutting back to side branches large enough to take over. It is not topping.

Crown restoration

Crown restoration is pruning done over several seasons to rebuild a sound crown on a tree that has been topped, torn by wind or snow, or badly pruned. It aims to choose new leaders from the sprouts and healthy limbs that remain and to space them so the crown regains a stable shape.

Crown thinning

Removing selected branches through the crown to reduce weight and wind load while keeping the tree's shape.

D

DBH (diameter at breast height)

The diameter of a trunk measured 4.5 feet above the ground. Wrap a tape around the trunk and divide by 3.14. Tahoe permit rules are written in DBH.

Dead wooding

Removing dead, dying and broken branches from a tree.

Decay

Wood breaking down from fungi inside a trunk, limb or root. It can be hidden behind sound-looking bark, which is why an arborist looks for cavities, conks and cracks.

Deciduous

A tree that drops its leaves each fall, such as a cottonwood, maple, elm or ash.

Defensible space

The area around a building where plants and other fuels are managed to slow a wildfire. The Living With Fire guide divides it into Zone 0 (0 to 5 feet), Zone 1 (5 to 30 feet) and Zone 2 (30 to 100 feet).

Dieback

Branches dying from the tips inward, often from drought stress, root damage or disease.

Directional felling

Directional felling is cutting down a tree so that it falls in a chosen direction, into a space cleared for it. It depends on a notch, a back cut and a hinge, and it is only used when there is room for the whole tree to come down without hitting anything.

Dormant season

The part of the year when a tree is not actively growing. Most deciduous trees are pruned in late winter, while dormant.

Drip line

The line on the ground under the outer edge of a tree's branches.

Drop zone

The cleared area where the crane sets down each section of a tree to be cut up and loaded.

E

Embers and firebrands

Embers, also called firebrands, are small burning pieces of vegetation and building material that the wind lifts and carries ahead of a wildfire. They land on roofs, in gutters, under decks and in vents, and are a leading way houses ignite during a wildfire.

End-weight reduction

End-weight reduction is pruning that removes some of the smaller branches and foliage at the outer end of a long or heavy limb, so less weight sits far from the trunk. It lowers the leverage on the limb and on the union where it attaches.

EPA-certified wood stove

An EPA-certified wood stove is a wood heater that has been tested and approved under U.S. Environmental Protection Agency rules to meet limits on particle smoke. Certified stoves carry a permanent label and burn cleaner than old uncertified ones, but only if they are fed dry wood.

Evapotranspiration

Evapotranspiration, or ET, is the total water that moves from soil and plants into the air: evaporation from the ground plus transpiration from leaves. It is the measure of how much water a landscape needs to stay alive.

F

Felling notch

A felling notch is a wedge-shaped cut made in the side of a trunk to set the direction in which the tree will fall. It is the first cut in a conventional felling and works with a back cut to control the fall through the strip of wood left between them.

Fire mitigation

Assessing a property's specific fire risks and removing fire fuel from around it to create a defensible zone.

Fire-adapted community

A fire-adapted community is a neighborhood or town whose residents and local agencies take steps together to cut wildfire risk, so that homes can survive a fire without heroic firefighting. It rests on each property doing its part and the neighbors doing theirs.

Fire-resistant plants

Fire-resistant plants are plants that are less likely to catch fire and feed it than others, usually because they hold more water, grow low and open, and shed little dead material. No plant is fireproof, and how a plant is kept matters as much as which plant it is.

Flush cut

A cut made tight against the trunk that removes the branch collar. It leaves a larger wound that closes poorly.

Frass

Frass is the mix of boring dust and droppings that insects leave behind when they feed inside or on a tree. It is one of the first visible signs that something is eating the wood or bark.

Fuel break

A fuel break is a strip or block of land where trees, brush and other fuels have been thinned or removed to slow the spread of a wildfire and give firefighters a place to work. It does not stop a fire by itself, but it changes how a fire behaves when it reaches the strip.

Fuel load

Fuel load is the amount of burnable plant material in an area, usually measured by weight per acre. It includes grass, brush, fallen limbs, dead standing trees, needles and leaves, and the heavier it is, the hotter and faster a wildfire can burn.

G

Girdling root

A root that circles the base of the trunk and squeezes it as both grow.

Graft union

A graft union is the place on a trunk where one tree, the scion, has been joined to the roots and lower trunk of another, the rootstock. It often shows as a slight bulge or scar a few inches above the soil, and it is the dividing line between two different plants.

H

Hardiness zone

A USDA map zone based on the average coldest winter temperature. Our service area runs from zone 6b to zone 7b on the 2023 map.

Heading cut

A cut that shortens a branch to a bud or a small twig rather than to a side branch. Repeated heading cuts on large limbs are topping.

Heartwood and sapwood

Sapwood is the outer, younger wood of a trunk that carries water up from the roots. Heartwood is the older, denser wood in the center that no longer carries water and mostly serves as support and storage for the tree's structure.

Hinge wood

Hinge wood, or the hinge, is the strip of uncut wood left between the felling notch and the back cut. It works like a door hinge: it holds the tree to the stump for a moment and guides it in the direction of the notch as it falls.

Home ignition zone

The home ignition zone is the home and its surroundings out to about 100 feet, the area where embers and flames are most likely to ignite a house. Research on wildfire losses points to what is inside this zone, more than the forest beyond it, as the main factor in whether a house survives.

I

Included bark

Bark trapped inside a tight fork between two stems. It keeps the wood from joining and is a common place for a tree to split.

ISA Certified Arborist

A credential issued by the International Society of Arboriculture to a person, not a company. Each holder has a certificate number, such as WE-11728A, that can be checked with the ISA. See what the credential means.

L

Ladder fuels

Low branches, shrubs and small trees that let a ground fire climb into the crowns of larger trees.

Lateral

A side branch. A proper reduction cut shortens a limb back to a lateral big enough to take over.

Leader

The main upright stem at the top of a tree.

Leaf scorch

Leaf scorch is browning or drying at the edges and tips of leaves, or between the veins, that happens when a leaf loses water faster than the roots can supply it. It is a symptom, not a disease, and heat, wind, dry or frozen soil and damaged roots are the usual causes.

Lean

The angle of a trunk away from vertical. A long-standing lean with a curved top is different from a new lean with lifting soil, which needs to be looked at right away.

Lion-tailing

Lion-tailing is the removal of most or all of the inner and lower side branches along a limb so that foliage is left in a tuft at the end, like the tail of a lion. It is not accepted pruning practice, because it moves weight to the end of the limb and invites failure.

Live crown ratio

Live crown ratio, or LCR, is the length of the living crown divided by the total height of the tree, usually given as a fraction or a percentage. A tall tree with a short live crown at the top has a low ratio; a tree with branches nearly to the ground has a high one.

Lot clearing

Removing trees, brush and debris from a parcel, for building, access or fire safety.

M

Mastication

Grinding standing brush and small trees into chips with a machine-mounted cutting head, leaving the chips on the ground.

O

Outriggers

The legs a crane or boom truck extends to steady itself before lifting.

P

Phreatophyte

A phreatophyte is a plant whose roots reach down to the water table or the moist zone just above it, so it can draw on groundwater instead of only on rain. The word comes from Greek for well plant, and in Nevada it covers cottonwoods, willows, greasewood and saltcedar.

Pile burning

Pile burning is the controlled burning of stacked brush, limbs and other slash, usually in the cooler or wetter part of the year when the risk of escape is lower. It is a way of disposing of cut vegetation where chipping or hauling is not practical, and it is regulated.

Pitch tubes

A pitch tube is a small, popcorn-shaped plug of resin on the bark of a pine, formed where a beetle bored in and the tree pushed resin out to fight it. Finding one tells you an insect attacked the tree; it does not tell you whether the attack succeeded.

Pollarding

Pollarding is a pruning system begun on a young tree, in which the new shoots are cut back to the same swollen knuckles at regular intervals, so the crown stays compact. It looks like topping but is a planned, repeated routine, and it cannot be started on a mature tree without harming it.

Prescribed fire

Prescribed fire is the deliberate, planned use of fire on a defined area, set by trained crews under written conditions to reduce fuels or restore a landscape. It is done by land management agencies, not by homeowners or tree companies.

R

Reaction wood

Reaction wood is the specialised wood a tree builds on a leaning trunk or a heavy, slanted limb to push it back upright or hold it in place. It forms in different spots in different kinds of trees.

Red flag warning

A Red Flag Warning is an alert from the National Weather Service that critical fire weather conditions are ongoing or expected soon. It is issued with land management agencies, and on those days even a small spark can start a fast-spreading wildfire.

Reduction cut

A reduction cut shortens a branch or stem by cutting it back to a side branch, called a lateral, that is large enough to take over as the new end. It reduces the length of the limb without leaving a stub or a ragged top.

Removal cut

A removal cut is a pruning cut that takes a whole branch off at its point of attachment, just outside the branch collar. It is the cut used when a limb should go entirely, as opposed to being shortened.

Rigging

The ropes, slings and hardware used to lower cut pieces of a tree under control.

Right-of-way

The strip of public land along a street, which often includes the area between the sidewalk and the curb. In Reno, work on trees in the City right-of-way needs a Tree Work Permit and a Certified Arborist.

Riparian trees

Riparian trees are trees that grow along the banks of rivers, creeks, ditches and other water. In Northern Nevada the typical ones are Fremont cottonwood, willows and some alder and aspen, which can reach groundwater that the surrounding desert lacks.

Root barrier

A panel set in the soil to steer roots away from pavement, pipes or foundations.

Root flare

The base of the trunk where it widens into the main roots. It should be visible at the soil line.

Root heave

Root heave is upward movement of soil or paving caused by roots. In everyday use it means a sidewalk, driveway or patio lifted by roots growing under it. In tree risk work it also describes soil rising on one side of a tree because the root plate is starting to tilt.

Root plate

The root plate is the area of roots and soil around the base of a tree, extending out from the trunk, that anchors it. It is the part that lifts out of the ground when a tree is blown over.

Root pruning

Root pruning is the deliberate cutting of tree roots, for example to make room for a wall, a path, a pipe or a building. Done carefully it lets a tree survive a project; done carelessly it kills the tree or leaves it ready to fall.

S

Seasoned firewood

Firewood that has been split and dried long enough to burn cleanly. Freshly cut wood is called green.

Sectional dismantling

Sectional dismantling is taking a tree down in pieces, working from the top, with each limb or trunk section cut and lowered under control rather than dropped. It is the usual way to remove a tree that stands near a house, wires, fences or other trees.

Shaping

Light pruning to keep a tree or shrub in a tidy, balanced form.

Skid steer

A compact wheeled loader that turns by skidding its wheels. Used for moving material, grading and snow.

Slash

The limbs, tops and brush left over from cutting. It is chipped, masticated or hauled so it does not become fuel.

Snag

A standing dead tree.

Speedline

A speedline is a taut rope or cable stretched at a slope from an anchor high in a tree to a lower point some distance away, along which cut pieces are slid sideways and down. It moves wood over a roof, pool or garden that the crew cannot lower pieces onto directly.

Stream environment zone

A stream environment zone, or SEZ, is a TRPA land category for the wet ground around streams, marshes and meadows in the Lake Tahoe Basin. It is protected because it filters the water that flows to the lake, so building, grading and heavy equipment are limited there.

Structural pruning

Pruning a young tree so it grows one strong central trunk and well-spaced branches. It is the usual pruning for young trees.

Structural root zone

The structural root zone is the area closest to the trunk that holds the large woody roots which keep the tree upright. It is smaller than the critical root zone, and damage inside it is a stability problem, not only a health problem.

Stub

A length of branch left sticking out past the collar after a poor cut. Stubs die back and invite decay.

Stump grinding

Grinding a stump below the surface with a machine so the area can be replanted or covered.

Stump removal

Taking out a stump. Most often done by grinding. Digging out the whole stump and root ball is a bigger job. See grinding versus full removal.

Surface fire

A surface fire is a wildfire that burns the fuels lying on or near the ground, such as grass, brush, needles, leaves and fallen limbs. It is the most common kind of wildfire, and it becomes more dangerous when it can climb into the tree crowns.

T

Tahoe BMPs

BMPs, or best management practices, in the Lake Tahoe Basin are the erosion and stormwater controls that the Tahoe Regional Planning Agency requires on properties to keep soil and runoff from reaching the lake. They include things like mulched bare soil, gravel drip areas and rock-lined channels.

Temperature inversion

A temperature inversion is a condition in which air near the ground is colder than the air above it, the reverse of the usual pattern. Cold air, and anything in it such as wood smoke, sits in the valley instead of mixing upward.

Topping

Cutting the top of a tree back to stubs. It weakens the tree and is not accepted pruning practice under the ANSI A300 standard. See why topping is not pruning.

Track loader

A compact loader on rubber tracks, such as our Bobcat T870. It carries logs, loads trucks and runs attachments like the masticating head.

Tree staking and guying

Tree staking and guying are ways of holding a tree upright with posts, or with straps and cables anchored in the ground, while its roots take hold or until a lean is corrected. They are temporary supports, not a repair for a tree that is failing.

TRPA

The Tahoe Regional Planning Agency. In the Tahoe Basin it requires a permit to remove a live tree over 14 inches DBH, or over 6 inches DBH between the house and the lake on lakeshore lots.

U

Utility and structure clearance

Pruning branches back from buildings, roofs and service lines.

Utility easement

A utility easement is a strip of land that a utility company has the legal right to use for its lines and equipment, even though the land belongs to someone else. Trees within it can be pruned or removed by the utility for the safety of the line.

W

Water sprouts and suckers

Fast, weakly attached shoots. Water sprouts grow from limbs, often after hard pruning or topping. Suckers grow from the roots or the base of the trunk.

Widow-maker

A broken limb hanging in a tree that can fall without warning. Also called a hanger.

Wildland-urban interface (WUI)

Neighborhoods and homes that are in or next to wildland vegetation.

Windbreak

A windbreak is a planting of one or more rows of trees and shrubs, set at right angles to the wind, that slows it and gives shelter on the downwind side. The protected area reaches a distance of several times the height of the trees.

Windthrow

A tree blown over at the roots, with the root plate lifted out of the ground.

Wood chips

What the chipper makes from limbs and brush. Used as mulch away from the house, never in Zone 0.

Woundwood

Woundwood is the ring of new wood and bark that a tree grows around the edge of a wound, such as a pruning cut, a broken limb or a scar. Over seasons it rolls inward to cover the exposed wood.

Z

Zone 0

The ember-resistant zone, 0 to 5 feet from the house. The Living With Fire guide says to remove woodpiles, combustible mulch, and junipers and other high-fire-hazard plants from it.

Zone 1

The lean, clean and green zone, 5 to 30 feet from the house in the Living With Fire guide.

Zone 2

The reduced fuel zone, 30 to 100 feet from the house in the Living With Fire guide, where dead vegetation and ladder fuels are removed.