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Complete Glossary List
*under construction*  Please email us @ if you have a term you'd like to see here. 
12-strand rope  For arborist ropes, a braided rope consisting of 12 strands. Most are coreless. There are two types of 12-strand construction: a tight braid that isn't easily spliceable, used for climbing and rigging lines; and a loose, easily spliceable braid, commonly used for slings. 
16-strand rope  For arborist ropes, a braided rope that has a 16-strand, load bearing cover and a filler core that isn't significant in load carrying. 
24-strand rope  For arborist ropes, a braided rope that has a 24-strand cover and is available in double-braided or kernmantle construction. 
3-strand rope  Rope construction in which three strands are twisted together in a spiral pattern. 
7-strand, common-grade cable  Steel-cable construction in which seven strands are twisted together in a spiral pattern. Used to add supplemental structural support to trees. Terminated by wrapping onto itself. 
abscission  Leaf or fruit drop induced by hormonal changes. 
access line  (1) Second climbing line hung in a tree in case it is needed to reach a victim in an emergency. (2) Climbing line installed in a tree to gain access to, but not used to work, the tree. 
action  Pertaining to carabiners and snaps, the number of distinct motions for the gate to be opened. A nonlocking carabiner is single action, requiring one movement for the gate to be opened. 
adventitious  Arising from parts of the root or stem and having no connection to apical meristems. 
aerial device (aerial lift device)  Truck with booms and a bucket for elevating a worker to the proximity of a tree's crown. 
aerial rescue  Method of bringing an injured worker down from a tree or aerial lift device. 
alkaline  Having a pH greater than 7.0. Contrast with acid. 
amon-eye nut  Specialized nut used in cabling trees that has a large eye for attaching a cable to a threaded rod. 
anchor  (1) In cabling, hardware to which support cable is affixed. (2) In rigging, the point at which the rigging system is secured or where friction is controlled. 
anchor hitch  Knot commonly used to attach a line to a piece of hardware. Anchor bend.

Learn how to tie an anchor hitch.

ANSI  Acronym for American National Standards Institute. 
ANSI A300  In the US, industry-developed national consensus standards of practice for tree care. 
ANSI Z133.1  In the US, industry-developed national consensus safety standards of practice for tree care. 
anthracnose  Group of fungal diseases of trees that affect the leaves, stems, flowers, or fruit, causing spotting, blotching, or necrosis. 
antitransprant  Substance applied to the foliage of plants to reduce water loss (transpiration). 
anvil-type pruning tool  Hand pruning tool with a sharps, straight blade that cuts against a flat metal surface. Cuts across fibers and may crush adjacent fibers. Intended for cutting single, small-diameter stems. Also called hand pruners or hand snips. 
aphid  Group of sap-sucking insects of the Hemiptera order. 
arboriculture  Practice and study of the care of trees and other woody plants in the landscape. 
arborist  Professional who possesses the technical competence gained through experience and related training to provide for or supervise the management of trees and other woody plants in residential, commerical, and public landscapes. 
arborist block  Heavy-duty pulley with an integrated connection point (bushing for attaching a rope sling), a rotation sheaves for the ropes, and extended cheekplates. Used in tree rigging operations. 
ascender  Piece of gear that enables a climber to ascend a rope. Attached to the rope, it will grip in one direction (down) and slide in the other (up). Contrast with descender
auger  Tool that bores holes in wood or other materials while carrying cuttings away from the bored hole. Fitted with a cross handle for hand use. 
auger bit  Tool that bores holes in wood or other materials while carrying cuttings away from the bored hole. Fitted with a hex, round square, or threaded shank for insertion into a power drill or driver. 
back cut  Cut made on a tree trunk or branch, opposite from the and toward the notch, face cut, or undercut, to complete felling or branch removal. Contrast with bore cut
bacteria  Single-celled organisms having a cell wall but no organized nucleus. A few species are plant pathogens. 
bactericides  Pesticides that are used to kill or inhibit bactera in plants or soil. 
balancer  Rigging sling(s), usually with at least one spliced eye and a Prusik to position the load line. Used to rig a limb in a balanced configuration. 
barber chair  Dangerous condition created when a tree or branch splits upward vertically from the back cut, slab up. 
bark  Protective outer covering of branches and stems that arises from the cork cambium. 
basal bark application  Application of herbicides, usually mixed with penetrating oil, to the lowest 12 to 18 inches (30 to 45 centimeters) of the main stems(s) of unwanted vegetation. 
bearing  Device, often relying on balls or rollers, to reduce friction between mechanical parts such as a wheel or a pulley sheave and an axle or a shaft and case connecting rod. Contrast with bushing. 
becket  An auxiliary attachment point on a block or pulley, usually 180 degrees from the main attachment, that is used to reeve the rigging line in a set of blocks. 
beer knot  Knot commonly used to join two ends of a piece of tubular webbing to create a loop. See water knot 
beer knot  Knot commonly used to join two ends of a piece of tubular webbing to create a loop. See water knot. 
belay  Means of securing or slowing a climbing line by using wraps around a cleat, carabiner, or other device. 
bend  Type of knot used to join two rope ends together. Contrast with hitch
bend radius  Radius of an object around which a line passes. 
bend ratio  Ratio of the diameter of a branch, sheave, or other object to the diameter of the rope that is wrapped around it. 
beneficial organisms  Insects and other organisms that assist in plant health, such as the control of pest populations. 
bight  Curve or arc in a rope between the working end and the standing part. 
Blake's hitch  Friction knot climbers use, sometimes in place of the tautline hitch or Prusik knot.

Learn how to tie a Blake's hitch. 

block  (1) Heavy-duty pulley used in rigging. Designed for dynamic loading. (2) Casing enclosing one or more parallel pullers. 
block and tackle  System of two or more pulleys with a rope or cable threaded between them, usually used to lift or pull heavy loads. 
bowline  Loop knot used to form single or double endline loop(s) in a rope, often to attach items to the rope. 
bowline on a bight  Knot used to form two loops in the standing part of a rope. 
branch  Stem arising from a larger stem. A subdominant stem. Pith in true branches has no connection to parent stem. 
branch union  Point where a branch originates from the trunk or another branch. Fork. Crotch. 
breaking strength  Force at which a new piece of equipment of rope fails under a static load. 
buck strap  Strap used in tree climbing, often employed for ascending trees with climbing spurs. Similar to a work-positioning lanyard. 
bucking  Cutting of a tree trunk or log into shorter, manageable sections. 
bud  Small lateral or terminal protuberance on the stem of a plant that may develop into a flower or shoot. Undeveloped flower or shoot containing a meristematic growing point. 
bull rope  Large-diameter rope used in rigging. 
buntline hitch  Simple hitch commonly used to attach a line to piece of hardware.

Learn how to tie a buntline hitch.

bushing  (1)Metallic tube or lining, without moving parts, to reduce friction between mechanical parts such as a pulley or sheave and an axle; also the nonrotating sheave used to increase the end radius for the sling attachment. Contrast with bearing. (2)A device, often made of rubber or plastic, to reduce vibration or wear between mechanical parts. (3)A fitting used to connect plumbing parts of different diameters (such as in spray equipment) 
butteryfly knot  Knot that can be used to form a loop in the standing part of a line. 
butt-hitching  Method of lowering pieces when the rigging point is below the work, traditionally without the use of a block. Contrast with blocking. 
buttress roots  Roots at the trunk base that help support the tree and equalize mechanical stress. 
butt-tying  Tying off a limb at the butt (larger) end for rigging. 
cabling  Installation of steel or synthetic cable n a tree to provide supplemental support to weak branches or crotches. 
caliper  Thickness or diameter of the trunk of a tree taken at a certain height. 
cambium  Thin layer(s) of meristematic cells that give rise (outward) to the phloem and (inward) to the xylem, increasing stem and root diameter. 
canker  Localized diseased area on stems, roots, and branches. Often shrunken and discolored. 
canopy  Collective branches and foliage of a tree or group of trees' crowns. Aggregate or collective tree crowns. A canopy can be closed or partially closed as in a forest or woodland stand, or composed of both individual trees and closed canopy groups as in an urban forest canopy. 
cant hook  Lever with an adjustable hook and having a blunt end instead of a spike. Used for handling and rolling logs. Traditionally made with a stout wooden lever but now often made of metal. Contrast with peavey 
carabiner  Connecting device. Oblong metal ring used in climbing and static rigging that is opened and closed by a spring-loaded gate. Contrast with snap 
central leader  Main stem of a tree, particularly of an excurrent specimen. 
chain-saw lanyard  Short rope or webbing lanyard used for securing a chain saw to a climber's saddle. 
chain-saw pants  Trousers manufactured with a protective layer designed to slow or stop a chain saw chain. See chaps 
chaps  Form of leg protection or personal protective equipment (PPE) worn when operating a chain saw, to protect from chain saw injury. 
chlorosis  Whitish or yellowish leaf discoloration caused by lack of chlorophyll. Often caused by nutrient deficiency. 
climbing hitch  Hitch used to secure a tree climber to the climbing line, which permits controlled ascent, descent, and work positioning. 
climbing line  Rope that meets specifications for use in tree climbing. 
climbing saddle  Work-positioning harness designed for climbing trees. 
climbing spurs  Sharp devices strapped to a climbers lower legs to assist in climbing poles or trees being removed. Also called spikes, gaffs, irons, hooks, or climbers. 
clove + half hitch  Combination of knots used to secure a rope to a tree section in rigging. 
clove hitch  Knot used to secure a rope to an object. 
codominant branches/codominant stems  Forked branches nearly the same size in diameter, arising from a common junction and lacking a normal branch union. 
command and response system  System of vocal communication used in tree care operations. 
common cable  In North America, flexible steel rope made up of seven wire strands that are twisted helically together. 
compression wood  Reaction wood in conifers that develops on the underside of branches or leaning trunks and is important in load bearing. 
conk  Fruiting body or nonfruiting body (sterile conk) of a fungus. Often associated with decay. 
connecting device  Mechanical connecting link. 
contact insecticides  Materials that cause insect injury or death on contact. 
control line  In speedlining, the line used to control the descent of the load on the speedline and to retrieve the pulley or traveler assembly. 
conventional notch  45-degree notch with a horizontal bottom cut. Used in removing trees or branches. Also called common notch. Contrast with Humboldt notch and open-face notch
Council of Tree and Landscape Apprasers (CTLA)  Group of representatives of several tree care and landscape associations that works to research and author the Guide for Plant Appraisal. 
cow hitch  Knot commonly used to attach hardware to a tree. Should be backed up or finished with a half hitch.

Learn how to tie a cow hitch.

crotch  (1) (noun) branch union or fork. (2) (verb) to place a line through a branch union. 
crown  Upper part of a tree, measured from the lowest branch, including all the branches and foliage. 
crown cleaning  In pruning, the selective removal of dead, dying, diseased, and broken branches from the tree crown. 
crown raising  In pruning, the selective removal of lower limbs from a tree crown to provide clearance. Raising. Lifting. 
crown reduction  Method of reducing the height and/or spread of a tree crown by making appropriate pruning cuts. Reduction. 
crown restoration  Method of restoring the natural growth habit of a tree that has been topped or damaged in any other way. Restoration pruning. 
crown thinning  In pruning, the selective removal of live branches to reduce crown density. 
cut-surface application  Method of placing herbicide on stumps immediately after cutting so that the herbicide is absorbed and translocated to the roots. Often used in utility arboriculture. 
cycles to failure  Number of times a rope or other piece of equipment can be used with a given load before mechanical failure. 
dbh  Acronym for tree diameter at breast height. Measured at 1.4 meters (4.5 feet) above ground in the United States, Australia (arboriculture), New Zealand, and when using the Guide for Plant Appraisal, 9th edition; at 1.3 meters (4.3 feet) above ground in Australia (forestry), Canada, the European Union, and in UK forestry; and at 1.5 meters (5 feet) above ground in UK arboriculture. 
DdRT  Acronym for doubled rope technique. Dynamic or static climbing system in which a rope is doubled over a branch and the climber utilizes both parts of the line. Contrast with DRT and SRT 
dead-end grips (tree grips)  Cable-termination devices that must be used to terminate extra-high-strength cable (EHS) tree support system cable to anchor hardware. May also be used with common-grade cable 
dead-end hardware  Lag-threaded cable anchor or bracing rod that is screwed directly into an undersized, pre-drilled hole in a tree but does not pass through to the other side. Contrast with through-hardware. 
dead-eye sling  Rope sling with a single eye spliced in one end. Also called eye sling, fixed-eye sling, or spliced-eye sling. 
deadwooding  Removing dead and dying branches from a tree. Outdated term for crown cleaning. 
decay  (1) (noun) an area of wood that is undergoing decomposition. (2) (verb) decomposition of organic tissues by fungi or bacteria. 
deciduous  Tree or other plant that sheds all of its leaves according to a genetically scheduled cycle as impacted by climate factors (usually during the cold season in temperate zones). Contrast with evergreen. 
decline  Gradually diminishing health or condition of a tree. 
deficiency  Pertaining to plant nutrition, lack or insufficient quantity of a required element. 
defoliation  Loss of leaves from a tree or other plant by biological or mechanical means. 
degree day  The difference between the daily average temperature and a given temperature base. 
descender  Device used to control friction when descending a climbing line. Contrast with ascender. 
diagnosis  Process of identifying a disorder by analyzing signs, symptoms, site conditions, patterns, climate, cultural history, and other factors to determine the causative agent(s). 
dicotyledon  Plant with two cotyledons in its embryo; netted or palmate leaf veins; and flowers with three, four, or five petals, or petals in multiples of these numbers. Contrast with monocotyledon. 
dieback  Condition in which the branches in the tree crown die from the tips toward the center. 
dielectric  Insulating (nonconducting) material. 
diffuse porous  Pattern of wood development in which the vessels and vessel sizes are distributed evenly throughout the growth ring. Contrast with ring porous. 
direct cable system  Simple tree cabling system joining two branches or leaders with a single cable. Contrast with box cable system and triangular cable system
directional pruning  Providing clearance by pruning branches that could significantly affect the integrity of utility facilities or other structures, and leaving in place branches that could have little or no effect. 
disease  Condition that impairs the performance of one or more vital functions. Usually associated with infectious agents. 
Distel  Type of friction hitch used in climbing and rigging.

Learn how to tie a Distel hitch.

dormancy  Period of naturally reduced physiological activity in the organs of a plant with the potential for reactivation of growth. 
dormant bud  Bud originally developed in a leaf axil and connected to the pith by a bud trace that has not been stimulated to mature and grow. Some buds remain dormant throughout the life of a woody plant. 
double braid  Rope construction consisting of a braided rope within a braided rope, both of which carry part of the load. 
double crotch  Technique consisting of tying one climbing line or two climbing lines into two places in a tree. 
double figure-eight knot  Figure-eight knot tied with a double strand of rope. 
double fisherman's bend  In arboriculture, the name used for a knot that is commonly used to join two ropes or two ends of the same rope, as when forming a Prusik loop. Grapevine knot. 
double half hitch  Two half hitches tied in a series. 
double hitch  Technique consisting of securing a tree section with two load lines in rigging. 
double-locking  Pertaining to a carabiner, requring two distinct motions to prepare the gate to open. 
downy mildew  White, fungal-like growth that develops during wet periods, usually on the underside of a leaf. 
drill-hole fetilization  Applying fertilizer by drilling holes in the soil within the root zone. Contrast with broadcast fertilization and liquid fertilization 
D-rings  D-shaped metal rings on a climber's saddle for attaching ropes and snaps. 
drip line  Imaginary line defined by the branch spread of a single plant or group of plants. 
drop cut  branch-removal technique consisting of an undercut and then a top cut, usually made farther out on the branch, or with a chain saw, directly over the undercut. 
drop line  Rope used to secure the weight of a limb in rigging; load line. 
drop start  Technique used to start a chain saw by pushing the saw away from the body and simultaneously pulling the start cord. 
drop zone  Predetermined area where cut branches or wood sections will be dropped or lowered from a tree. See landing zone 
drop-crotch pruning  (obsolete) Term for a method of reducing the height of a tree. The general rule for cuts is that leaders should be cut back to a lateral capable of assuming apical dominance, if possible, usually at least one-third the diameter of the leader. See reduction
DRT  Acronym for double rope technique. Climbing system n which two separate ropes and two separate anchor points are utilized. Contrast with DdRT and SRT. 
dynamic cable system  Simple tree cabling system joining two branches or leaders with a single cable. Contrast with box cable system and triangular cable system. 
dynamic load  Forces created by a moving load. Load that changes with time and motion. Contrast with static load. 
earth auger  Drill bit with a wide, threaded shank used for drilling holes in the ground. See soil auger. 
ectomycorrhizae  type of mycorrhizae that grow between the cortical or epidermal cells of absorbing roots, forming an outer sheath around the root. See mycorrhizae Contrast with endomycorrhizae
edema  Watery swelling in plant tissue. 
EHS Cable  see extra-high-strength cable. 
emergency response  Predetermined set of procedures by which emergency situations are assessed and handled. 
endomycorrhizae  type of mycorrhizae that grow within root cells. See mycorrhizae. Contrast with ectomycorrhizae 
epinasty  Downward curling of the leaf blade resulting from more rapid cell growth on the upper side of the petiole than on the lower side. Often a symptom of plant disease. Distortion of growth, often caused by certain types of herbicides. 
espalier  (1) (noun) Specialized technique of pruning and training plants to grow within a plane, such as along a wall or a fence. (2) (noun) A plant trained in that manner. (3) (verb) To train plants in that manner. 
essential elements  17 minerals essential to the growth and development of trees. These minerals are essential because plants cannot complete their life cycle without them. See macronutrient, micronutrient, and primary elements. 
ethephon  Plant growth regulator used to promote fruit ripening. Also stimulates later flow in rubber trees. 
evergreen  Tree or other plant that does not shed all of its foliage annually. Contrast with deciduous. 
exotic species  Not native or indigenous to a region. May be invasive. Contrast with introduced species, native species, and naturalized species
extra-high-strength (EHS) cable  Type of 7-strand steel cable, other used to cable trees. Stronger but less flexible than common-grade cable. Must be terminated with dead-end tree grips. 
eye bolt  Cable anchor with a closed eye, usually machine threaded. Only drop-forged eye bolts are accepted and approved for tree support systems in the United States. 
eye splice  (1) in cabling, a closed termination loop, hand formed in common-grade cable by wrapping the successive strands back upon the standing part to attach the cable to anchor hardware. (2) a splice that forms a closed eye or loop. 
eye-to-eye sling  Eye-to-eye sling: sling (usually a length of spliced rope) with an eye at each end. Also called eye-and-eye sling. 
face cut  Notch cut used to help control the direction of fall of trees or branches being removed. 
failure potential  In tree risk assessment, the professional assessment of the likelihood for a tree or tree part to fail within a defined period of time. 
fall protection  Equipment and techniques designed to ensure a climber will not fall from a tree or an aerial lift. 
false crotch  Device installed in a tree to hold and direct ropes during climbing or rigging because there is not a suitable natural crotch available, or to protect an available crotch, and/or to reduce wear on ropes. 
felling  Dropping or cutting down a tree. 
felling wedge  A metal or plastic wedge inserted into the back cut to help direct to path in which a tree or tree part falls. 
fertilization  Application of essential elements to a plant, usually through the soil. 
figure-8 descender  Metal device used to provide friction on a rope in climbing or very light rigging. See descender
figure-8 knot  Particular knot tied as a safety knot of stopper knot at the end of a line. 
fixed loop  Webbing or rope sling consisting of a complete, closed loop. 
fixed-eye sling  Short sling with an eye spliced in one end. Also called dead-eye sling. 
flip line  Tree climbing lanyard, with or without a wire core, usually with a snap or carabiner at one end and an eye at the other end. Used for ascending trees when using spikes, for work positioning, and as a second means of life support when using a chain saw in a tree. 
floating anchor  Anchor point in a rigging system that can be moved anywhere between two points. 
floating false crotch  False crotch installed on an ascent line anchored high in a tree. 
flush cut  Pruning cut through and/or removing the branch collar, causing unnecessary injury to the trunk or parent stem. 
foliage  Leaves of a plant. 
foliar application  Applying a fertilizer, pesticide, or other substance directly to the foliage. 
footlock (footlocking)  Method of ascending a rope by wrapping the rope around the feet. See secured footlock 
free climb  Climbing a tree without being secured by a climbing rope. 
French Prusik  Type of friction hitch used in climbing and rigging. 
friction  specific type of force that resists the relative motion between two objects in contact. The direction is always opposite the motion. 
friction device  Device used to take wraps in a load line to provide friction for controlled lowering or climbing. 
friction hitch  Any of numerous knots used in tree climbing or rigging that may alternately slide along and then grip a rope. 
friction saver  Specific types of false crotch used for climbing trees; two rings connected by a strap. 
frost crack  Vertical split in the wood of a tree, generally near the base of the bole, caused by internal stresses and low temperatures. Radial shake. 
fruiting body  Reproductive structure of a fungus. The presence of certain species may indicate decay in a tree. See conk 
fungicides  Chemical compounds that are toxic to fungi. 
fungus (pl. fungi)  Group of organisms from the kingdom of Fungi, including yeasts, molds, mushrooms, and smuts. Typically multicellular, saprophytic, or parasitic and lacking vascular tissue and chlorophyll. Reproduces by spores borne in fruiting bodies. 
gaff  Pointed, spur portion of a climbing spike. 
gall  Abnormal swelling of plant tissues caused by gall wasps, mites, nematodes, and various insects and less commonly by fungi or bacteria. Contrast with burl 
gate  Mechanism to control the opening and closing of a connecting device. See carabiner and snap
girdling  Restriction or destruction of the vascular system within a root, stem, or branch that causes an inhibition of the flow of water and photosynthates in the phloem. 
girdling root  Root that encircles all or part of the trunk of a tree or other roots and constricts the vascular tissue and inhibits secondary growth and the movement of water and photosynthates. 
girth hitch  Simple knot used to attach a line, spliced eye, or endless loop to an object. 
GRCS  acronym for Good Rigging Control System, the brand name of a friction device used in rigging. 
growth rate  Speed at which something grows. 
guy  (1) a steel or synthetic-fiber cable between a tree or branch and an external anchor (another tree, the ground, or other fixed object) to provide supplemental support. (2) a steel cable between a utility pole and an external anchor (another pole, the ground, or other fixed object, which may sometimes be a tree) to keep the pole upright. Guys act in tension. Contrast with prop. 
half hitch  Simple knot used to temporarily attach a line to an object. Also used as a backup in combination with other knots. 
hand pruning shears  Tool used for pruning twigs of less than 1/2 inch (1.3 cm) diameter. 
hanger  Broken or cut branch that is hanging in a tree. 
hard lay rope  Rope manufactured with tightly wound strands, making it stiffer than standard lay or soft lay ropes. 
Haven grip  Device used to clasp and hold cables. 
hazard  Situation, condition, or thing that may be dangerous. (1) in tree management, a tree or tree part that is likely to fail and cause damage or injury, and the likelihood exceeds an acceptable level of risk. (2) in tree care or forestry operations, the presence of a condition or situation that may cause harm or injury to workers or others. 
hazard assessment  Systematic process of identifying hazards. See risk assessment. 
hazard reduction pruning  Type of pruning to remove dead, severely decayed, split, or other unsafe branches. 
heading (heading back)  Cutting a shoot back to a bud or cutting branches back to buds, stubs, or lateral branches not large enough to assume apical dominance. Cutting an older branch or stem back to a stub in order to meet a structural objective. 
heart rot  Any of several types of fungal decay of tree heartwood, often beginning with infected wounds in the living portions of wood tissue. 
heartwood  Wood that is altered (inward) from sapwood and provides chemical defense against decay-causing organisms and continues to provide structural strength to the trunk. Trees may or may not have heartwood. Contrast with sapwood. 
heartwood rot  Any of several types of fungal decay of tree heartwood, often beginning with infected wounds in the living portions of wood tissue. Also called heart rot. 
herbicides  Chemical compounds that kill vegetation. 
hinge  Strip of uncut wood fibers created between the face cut or notch and the back cut that helps control direction in tree felling or limb removal. Holding wood. 
hinge cut  Sequence of cuts used to control the direction of a limb being removed. 
hitch  (1) type of knot made when a rope is secured around an object or its own standing part. Contrast with bend. (2) a mechanical device for connecting a towing vehicle to a trailed or towed vehicle or implement. 
holding wood  Section of wood located between the face cut and the back cut that helps direct where the tree will fall. See hinge 
hollow braid  Rope construction consisting of a braided rope with no core. 
honeydew  Sugary substance secreted by certain insects, including aphids and some scale insects, when feeding on plants. 
horizontal boring  Boring, with special machinery, below the surface of the ground without an open trench. Alternative for installation of underground utilities that avoids cutting of tree roots or damage to hardscape or existing utilities. Contrast with radial trenching, trenching, and tunneling
horticultural oils  Highly refined petroleum oils that may be applied to plants to smother certain insects and other pests by disrupting their respiration. 
host  Living organism from which a parasite obtains nutrition. 
Humboldt notch  Felling notch that is horizontal on the top and angled on the bottom. Also called Humboldt scarf or reverse scarf. Contrast with conventional notch and open-face notch. 
hydrogels  Crystalline polymers tat absorb water and, if needed, can be added to the soil to increase its water-holding capacity. 
included bark  Bark that becomes embedded in a crotch (union) between branch and trunk or between codominant stems. Causes a weak structure. 
increment borer  Device used to take core samples from trees to determine age or detect problems, such as decay. 
inoculants  In soil science, microorganisms (e.g., mycorrhizae fungi) that are introduced into the soil in order to improve growth or plant health. 
insecticidal soaps  Soap-based pesticides approved for application to plants to kill insects and certain mites by disrupting the cell membranes. 
insecticides  Substances toxic to insects. 
instar  Stage of growth between molts in the development of insect larvae. 
Integrated Pest Management (IPM)  Method of controlling plant pests by combining biological, cultural, mechanical, physical, and/or chemical management strategies. 
Intergrate Vegetation Management (IVM)  System of managing plant communities in which compatible and incompatible vegetation are identified, action thresholds are considered, control methods are evaluated, and selected control(s) are implemented to achieve a specific objective. Choice of control methods is based on effectiveness, environmental impact, site characteristics, safety, security, and economics. 
invasive species  Non-native organisms likely to spread, disrupting the natural balance of an ecosystem. 
kerf  Slit or cut made by a saw in a log. Space created by a saw cut. 
kerf cuts  Cuts made to prevent fiber tearing from a branch or trunk section being removed. 
kernmantle rope  Rope construction with a cover and a core in which the core yarns are not braided. 
key lock  In carabiners, a specific configuration of the gate latch designed not to catch on ropes. Contrast with tooth lock. 
kickback  Sudden, sometimes violent and uncontrolled, backward, or upward movement of a chain saw. 
kickback quadrant  Upper quadrant of the tip of a chain-saw bar. 
kilonewton (kN)  Unit of force. Amount of force required to move 1,000 kilograms a single meter in a single second (equals 224.8 pounds of force). 
knot  Any of various fastenings formed by looping and tying a rope (or cord) upon itself or to another rope or to another object. 
knotless system  Rigging system in which loop slings and connecting links are used to attach branches or wood sections to the lowering line. 
lag eye  Lag-threaded cable anchor with a closed eye. 
lag hook (J-hook)  Lag threaded cable anchor with an open eye (J-shaped). 
lanyard  Short rope equipped with carabiners, snaps, and/or eye splices. Work-positioning lanyards are used for temporarily securing a climber in one place. 
larva  Immature life stage of an insect between the egg and the pupa stage. 
latent bud  Bud held in dormancy for more than one year by hormones originating from the terminal bud. Term sometimes used to refer to dormant buds or adventitious buds. 
leach (leaching)  (1) tendency for elements or compounds to wash down through the soil. (2) tendency for elements or compounds to wash into the soil. For example, alkaline compounds may leach from concrete, or heavy metals may leach from aggregates, and both may damage plants. 
leader  Primary terminal shoot or trunk of a tree. Large, usually upright stem. A stem that dominates a portion of the crown by suppressing lateral branches. 
leaf margin  Outer edge of the leaf blade. 
leaf spot  Patches of disease or other damage on plant foliage. 
lenticel  Small opening in the bark that permits the exchange of gases. 
lifting cut  Variation of the hinge-cut technique used to cut limbs that are being lifted. 
lignin  Organic substance that impregnates certain cell walls to thicken and strengthen the cell to reduce susceptibility to decay and pest damage. 
limbing  Cutting off the side branches of a felled tree. See crown raising
line  (1) rope that is configured, constructed, or intended for or assigned or restricted to a particular use (e.g., climbing line or lowering line). (2) a wire or cable designed to conduct electricity. (3) pertaining to electric utilities, the wires that serve as electrical conductors in an electric utility circuit. 
lion tailing (lion's tailing)  Poor pruning practice in which an excessive number of branches are thinned from the inside and lower part of specific limbs or a tree crown, leaving mostly terminal foliage. Results in poor branch taper, poor wind load distribution, and a higher risk of branch failure. 
locking  Pertaining to carabiners and snaps, requiring at least one distinct motion to prepare the gate to open (to unlock but not to actually open). 
locking snap  Snap that is self-closing and requires one motion to unlock and a separate motion to open the gate. Used by tree climbers primarily for connecting the climbing line to the saddle. 
loopie  Specific type of sling made up as an adjustable loop. 
Machard  Type of friction hitch used in climbing and rigging. 
Machard tresse  Type of friction hitch used in climbing and rigging. 
machine-threaded  Cable anchor or bracing rod with a fine-thread pattern that is used with a nut and washer and installed through a pre-drilled hole that is larger in diameter than the rod. Contrast with lag-threaded
macroinfusion  Trunk injection technique that requires a relatively large-diameter hole in the trunk. Contrast with implant, macroinjection, and microinjecton. 
macroinjection  Trunk injection technique that requires a relatively large-diameter hole in the trunk. Contrast with implant, macroinfusion, and microinjection 
marline hitch  (1) simple hitch used in lashing. (2) in rigging, a secondary knot used in combination with a primary attachment knot to tie off sections for lowering. 
marline spike  Tool that tapers to a point. Used for separating the strands of a rope in splicing and in marling. 
microinjection  Trunk injection technique using a small-diameter trunk penetration to introduce chemicals directly into the xylem. Contrast with implant, macroinfusion, and macroinjection
micronutrient  Essential element that is required by plants in relatively small quantities. Contrast with macronutrient 
micropulley  Small, light-duty pulley used in climbing operations. Often used as a knot tender. 
minimum breaking strength  Minimum load under which a new, unused rope or other piece of equipment will fail. Based on multiple trials and, for ropes, calculated as three standard deviations below the mean. 
mites  Small, often minute, arthropods n the order Acarina of the class Arachnida that may feed on plants, other mites or small insects. 
miticides  Chemical compounds that are toxic to mites. 
monoculture  The cultivation or planting of a single species on agricultural land, in a forest setting, or within an urban landscape. 
moving block  In a mechanical advantage pulley system, the pulley that moves. 
Muenter hitch  Hitch commonly used to belay a climber. 
mulch  Material that is spread or sometimes sprayed on the soil surface to reduce weed growth, to retain soil moisture and moderate temperature extremes, to reduce compaction from pedestrian or vehicle traffic or to prevent damage from lawn-maintenance equipment, to reduce erosion or soil splattering onto adjacent surfaces, to improve soil quality through its eventual decomposition, and/or to improve aesthetic appearance of the landscape. Mulch can be composed of chipped, ground, or shredded organic material such as bark, wood, or recycled paper; unmodified organic material such as seed hulls; organic fiber blankets or mats; or inorganic material such as plastic sheeting. See green mulch. 
mycorrhizae  Symbiotic association between certain fungi and the roots of a plant. 
natural (target) pruning  Process of branch removal n which the pruning cuts are made at nodes and in relation to the positions of the branch collar and branch bark ridge. 
natural-crotch rigging  Rigging methods that utilize natural crotches for the rigging points. 
nematode  Microscopic roundworm. Many are beneficial organisms, but some feed on plant tissues and may cause disease or damage. 
nontarget organism  an organism that is not intended to be damaged or killed by a pesticide, but that may still be susceptible to its effects. 
notch gate  In carabiners, a type of gate latch mechanism. Also called pin lock or or tooth lock. Has the disadvantage that it may catch on a rope. Contrast with key lock. 
open-face notch  Wedge-shaped cut (approx 70 degrees or greater) used in felling trees or removing, tree sections. Contrast with conventional notch and Humboldt notch 
organic  In chemistry, a substance containing carbon. In an applied arboricultural context, a substance, especially a fertilizer or pesticide, of animal or vegetable origin. Contrast with inorganic. 
OSHA  In the United States, the legislative act dealing with health and safety in the workplace; administered by the Occupational Safety and Health Administration; in Canada, Occupational Health and Safety Administration (OHSA) 
outriggers  Projecting structures used for stabilization on aerial devices, cranes, and other vehicles that support elevated or outstretched loads. 
peavey  Lever with an adjustable hook and a sharp spike instead of a blunt end. Used for handling and rolling logs. Traditionally made with a stout wooden lever but now often made of metal. Named for its inventor Joseph Peavey. Contrast with cant hook 
Personal Protective Equipment (PPE)  Personal safety gear such as hard hat, safety glasses, hearing protection, and leg protection, including chaps. 
pest  Organism (including, but not limited to, weeds, insects, or fungi) that is damaging, noxious, or a nuisance. 
pesticide  Any chemical used to control or kill unwanted pests such as weeds, insects, or fungi. 
pesticide resistance  Ability to withstand certain pesticides; survival of just a few genetically resistant pests that reproduce can lead to populations that are resistant. 
pH  Unit of measure that describes that alkalinity or acidity of a solution. Negative log of the hydrogen ion concentration. Measured on a scale. 
phloem  Plant vascular tissue that transports photosynthates and growth regulators. Situated on the inside of the bark, just outside the cambium. Is bidirectional (transports up and down). Contrast with xylem 
photosynthesis  Process in green plants (and in algae and some bacteria) by which light energy is used to form glucose (chemical energy) from water and carbon dioxide. 
phytotoxic  Term to describe a compound that is poisonous to plants. 
plant grown regulator  Compound effective in small quantities that affects the growth and/or development of plants. May be naturally produced (hormone) or synthetic. See plant hormone
Plant Health Care (PHC)  Comprehensive program to manage the health, structure, and appearance of plants in the landscape. 
plunge cut  Using the tip of a chain saw to cut into or through the middle of a piece of wood. Back-cut technique in which the hinge is established by cutting through the stem behind the notch then cutting back away from the hinge. Bore cut. 
pole pruner  Long-handled tool used to make scissor like, small pruning cuts that cannot be reached with hand tools. 
pole saw  Long-handled tool with a pruning saw on the end. 
pollarding  Specialty pruning technique in which a tree with a large-maturing form is kept relatively shorts. Starting on a young tree, inter-nodal cuts are made at a chosen height, resulting in the development of callus knobs at the cut height. Reguires regular (usually annual) removal of the sprouts arising from the cuts. 
Port-a-Wrap III  Brand name for the third generation of a device used to create and manage friction in the lowering line (load line) in rigging operations. 
positive-locking  (obsolete) In reference to carabiners and snaps, locking automatically and requiring two or more motions to prepare the gate to open. Prevents unintentional opening. 
powdery mildew  Any of various fungi of the genus Erysiphe producing powdery conidia that appears as a white, fuzzy coating on the upper leaf surfaces, often causing distortion of the leaf. 
Preformed Tree Grip  Brand of dead-end grip. 
pruning  Removing branches (or occasionally roots) from a tree or other plant using approved practices, to achieve a specified objective. 
pruning saw  Hand saw designed for pruning trees, generally with a bowed blade and teeth oriented for cutting on the pull stroke. 
Prusik hitch  Type of multi-wrapped friction hitch used in climbing and rigging. A common used it to attach the Prusik loop to the climbing line when footlocking. 
Prusik loop  Loop of rope used to form a Prusik hitch for climbing or rigging. 
Prusik minding  Specific type of pulley configured with extended cheekplates to keep a Prusik hitch from jamming in the sheave. 
pull line (tagline)  Line attached near the top of a tree to be felled or section of a tree to be removed to help pull or guide t in the desired direction or to control its swing. 
pulley  Device consisting of a rotating, grooved wheel between two side plates. Used to change the direction of pull in a line. May be used as part of a mechanical advantage system. Compare to block
quick-release fertilizer  Fertilizer with less than 50 percent water-nsoluble nitrogen (WIN). Contrast with slow-release fertilizer. 
redirect  (1)(verb) Changing the path of a climbing or rigging line to modify the forces on, or the direction of, the line. (2)(noun) A system installed to change the path of a climbing or rigging line. 
reduction  Pruning to decrease height and/ or spread of a branch or crown. See drop-crotch pruning. 
rescue kit  Climbing gear and emergency equipment that should be set out on every job site and available to conduct an aerial rescue and apply first aid. 
rescue pulley  Light-duty pulley used in light rigging operations. 
resistance  (1) In plants, the tendency to withstand, or to not develop, certain pest (including disease) problems; pest resistance. (2) In insects, the ability to withstand certain insecticides; survival of just a few genetically resistant insects that reproduce can lead to populations that are resistant. (3) In other pests, the ability to withstand certain pesticides. 
Resistograph  Brand name of a device consisting of a specialized micro-drill bit that drills into trees and graphs density differences that are used to detect decay. 
retreat path  Predetermined escape route away from a tree that is to be felled. Should be a 45-degree angle back and away from the direction of the falling tree and clear of obstruction. 
rhizosphere  Soil area immediately adjacent to, and affected y, plant roots. Typically has a high level of microbial activity. 
rigging  Method of using ropes and hardware (1) in tree pruning or removal, to control or direct the descent of cut material or to handle heavy loads. (2) with cranes, loaders, or other equipment, to life heavy loads. 
rigging line  Rope, usually the load line, used in rigging operations. 
rigging point  Placement in the tree (in a natural or false crotch) or any other point through which the load line passes to control rigging operations. 
ring porous  Pattern of wood development in which the large-diameter vessels are concentrated in the earlywood. Contrast with diffuse porous. 
root pruning  (1) in transplanting, the process of pre-digging a root ball to increase the density of root development within the final root ball. (2) in tree conservation and preservation, the process of pre-cutting roots behind the line of a planned excavation to prevent tearing and splintering of remaining roots. (3) in tree disease management, severing tree roots to prevent disease transmission through root grafts. 
root:shoot ratio  Relative proportion of root mass to crown mass. 
rope  A construction of braided or twisted strands to form a thick cord. See line
rope bag  Bag used to store climbing and rigging lines. 
rope sling  Length of rope, usually with at least one eye splice, used to secure equipment or tree sections in rigging operations. 
running bowliner  Bowline knot with the standing part of the line running through the loop. Often used to tie off and control branches or tree sections that are to be removed. Can be used when the desired tying point cannot be directly accessed by the worker. 
running end  End of a rope not in use. Contrast with standing part and working end
rust  Disease caused by a certain group of fungi and characterized by reddish brown spots on the foliage and/or the formation of stem galls. 
safety eyeglasses  Protective lenses that must be worn when conducting tree care operations. 
safety lanyard  A short rope equipped with snaps used for temporarily securing a climber in one place. 
scabbard  Protective sheath for a pruning saw or other tool. 
scaffold  (1)Pertaining to tree architecture or form, a strong and properly spaced arrangement, framework, or system of branches throughout the crown. (2)A work platform, which may be stationary or moving. 
scale  One of a group of insects that attach themselves to plant parts and suck the sap. 
Scwabisch  Type of friction hitch used in climbing and rigging. 
secured footlock  Method of footlocking in which the climber utilizes an additional means of securing against a fall. See footlock 
selective herbicides  Herbicides that are effective only on specific plant types (e.g., broadleaves, grasses) or species. 
shackle  U-shaped fitting with a pin running through it. Clevis 
sheave  Inner fitting within a block or pulley over which the rope runs. 
sheepshank  Knot used to form a loop in the middle of a line or to shorten a line. 
sheet bend  Knot used to attach two lines. The lnes can be of unequal diameter. Not to be used for life support. 
ship auger  Type of drill bit with an open spiral form. Used to drill holes in trees for cable or bracing installation. 
shock-loading  Dynamic, sudden force placed on a rope or rigging apparatus when a moving load or piece is stopped. 
single action  Pertaining to carabiners and snaps, requiring one motion for the gate to open. A nonlocking carabiner is single action. 
single rope technique (SRT)  A set of methods used to ascend (or descend) on a single leg of a single rope. 
slack tender  Any of several devices used to facilitate taking up slack in the climbing line. 
sling  Device used in rigging to secure equipment or pieces being rigged. 
slippery bend  Knot used to attach two lines that can be released quickly by pulling on the final tucked bight. 
slow-release fertilizer  Fertilizer that is at least 50 percent water-insoluble nitrogen (WIN). Rate of release may vary depending upon soil moisture and temperature. Contrast with quick-release fertilizer. 
snap  Connecting device used by tree climbers, primarily for connecting the climbing line to the saddle. Contrast with carabiner
snap cut  Cutting technique in which offset, bypassing cuts are made so that a section can be broken off easily. See mismatch cut. 
snatch block  Kind of block (pulley) that can be opened on one side to receive the bight of a rope. 
snatching  Rigging operation in which a section of upright stem is lowered off itself using a block or strop. 
soil amendment  Material added to soil to improve its physical, chemical, and/or biological properties. 
soil analysis  Analysis of soil to determine pH, mineral composition, structure, salinity, and other characteristics. 
soil auger  (1) Device for removing cores of soil for inspecting or testing. (2) Device (drill bit) used to drill holes in the soil for vertical mulching or for the drill-hole methods of fertilizing. See earth auger. 
soil compaction  Compression of the soil, often as a result of vehicle or heavy-equipment traffic, that breaks down soil aggregate and reduces soil volume and total pore space, especially macropore space. 
soil horizon  Layer or zone of the soil profile with physical, chemical, and biological characteristics that differ from adjacent layers. 
soil-drench application  Method of applying chemicals (usually herbicides or tree growth regulators) to trees through the soil. Normally done by excavating a shallow trench in the soil around the base of the trunk and pouring the compound into the trench. 
sooty mold  Fungus that appears as a black, sticky coating on the surface of leaves, fruits, branches, and other surfaces resulting from deposits of sugary excrement from aphids and scale insects. 
spear cut  Quickly cutting an upright branch so that it descends upright. 
speedline  Rigging line strung in such a way as to allow tree segments to slide to the ground at a distance away from the base of the tree and the drop zone for an ordinary lowering line. 
topping  Inappropriate pruning technique to reduce tree size. Cutting back a tree to a predetermined crown limit, often at internodes. 
Tree  A plant having a permanently woody main stem or trunk, ordinarily growing to a considerable height, and usually developing branches at some distance from the ground.