Tree Vocabulary – W & X


Water Jet – A procedure that uses high-pressure water and a probe to create air passages in the soil. Primary reason for use is mitigation for compacted soil. Water Jet can be used in conjunction with liquid fertilization only when soil and leaf tissue analysis indicate nutrient limitation.
Watersprout – Vigorous, upright shoot that arises from a latent or an adventitious bud above the ground or graft union on older wood.
Wetwood – Wood altered to a higher state of protection against mechanical disruption or decay by pathogens that make the wood so high in moisture, pH, and microelements that decay-causing pathogens are not able to infect. A disease of wood caused mostly by bacteria.
Wilting Point – That level of soil moisture at which wilted plants are able to recover following addition of water. Contrast with permanent wilting point.
Wound – An opening that is created when the tree’s protective bark covering is penetrated, cut, or removed, injuring or destroying tissue. Pruning a live branch creates a wound, even when the cut is properly made.
Woundwood – Differentiated woody tissue that forms after initial callus has formed around margins of a wound.
Wounds are closed primarily by woundwood.
Xylem – Tissue produced by the activity of the cambium and composed of tracheids, wood fibers, and parenchyma cells, which function to transport and store water and mineral elements as well as to provide mechanical support.

Tree Vocabulary – U & V


Union (Crotch) – The junction between stem and branch or between stems. 


Vactor Truck – A truck equipped with a large tank and vacuum unit able to remove loose soil or soil-water slurry. Used with water or air pressure to remove soil around tree roots. This equipment is used to remove soil or soil slurry when excavating around tree roots. VTA (visual tree assessment)- Method of evaluating structural defects and stability in trees.
Vertical Core Venting – A procedure that creates vertical holes, usually about 2-inches in diameter, that extend down through compacted soil. The holes can be from 18-inches to over 3-feet deep. Holes are spaced from 6-inches to 2-feet depending upon the site soil conditions. Holes are created with an auger, water jet or using an air spade. 
Vigor – Overall health; the capacity to grow and resist physiological stress.

Tree Vocabulary – S


Sandy Loam – A soil containing much sand, but which has enough silt and clay to make it somewhat coherent. The individual sand grains can be readily seen and felt.
Sapwood – The outer portion of the wood that has living cells and transports water and nutrients and stores carbohydrates.
Saturation – In soil moisture, the condition in which both macro- and micropores are filled with water.
Scaffold – A large limb that is or will be part of the permanent branch structure of a tree.
Scarified – Soil that has been loosened or mechanically disturbed.
Silt Loam – A soil having a moderate amount of the fine fractions of sand and only a small amount of clay, over half of the particles being of silt size.
Sinker Roots – Roots that grow vertically from horizontal roots, adding stability to the tree and increasing the volume of deeper soil exploited by the roots.
Species – A group of plants that resemble each other closely and that interbreed freely.
Spiral of Decline
Starch – A chain of sugars linked together that stores energy for later use by the plant.
Stem – A woody structure bearing foliage and buds that gives rise to other stems.
Stomata – Minute opening in the leaves through wihich gas exchange, including water vapor and carbon dioxide, occurs.
Stress and Strain – Stress is a potentially injurious, reversible condition, caused by energy drain, disruption, or blockage, or by life processes operating near the limits for which they were genetically programmed. When stress goes to strain, the tree dies; Generally attributed to over-pruning and root loss due to construction activity.
Structural Pruning – Pruning that influences the orientation, spacing, growth rate, strength of attachment, and ultimate size of branches and stems.
Structural Soil – Also known as “gap graded soil”. A mix of rock and soil that is used to provide surface support for hardscape without eliminating soil gas exchange.
Suckers – Adventitious stems arising from the lower trunk or roots.
Symbiotic – The relationship of two dissimilar organisms living together to the mutual benefit of each other.

Tree Vocabulary – R


Radial Trenching – A method used to mitigate and replace soil inside the tree root protection zone. Soil is removed from trenches that are 8-12 inches wide and 18-36 inches deep. Trenches are excavated in direct lines toward the base of the tree using air spade, hydraulic excavation or hand careful hand excavation. Backfill can be amended soil, structural soil, a mix of sand and compost, or any combination deemed to be appropriate for the situation.
Raising – Selective pruning to provide vertical clearance; also known as lifting.
Reducing – Pruning to decrease height or spread on entire tree or one section; also referred to as reduction or reduced pruning.
Reaction Wood – Specialized secondary xylem that develops in response to lean or similar mechanical stress, to restore the stem to the vertical. Occurs as compression wood in conifers and tension wood in angiosperms.
Reduction Cut (Drop-Crotch Cut, Lateral Cut) – Reduces the length of a branch or stem back to a live lateral branch large enough to assume the apical dominance- typically at least one-third the diameter of the cut stems.
Restoring – The process of improving the structure of a tree that was preciously topped, damaged, vandalized, lion tailed or overthinned.
Resistograph – A tool which uses a small, pressure sensitive bit to penetrate a tree from the outside to determine the thickness of sound wood surrounding a suspected decay deposit.
Root – An organ of a tree that serves to maintain mechanical support, to provide water and essential elements from the soil through absorption, and to store energy reserves.
Root Ball – Refers to the root system of a container or balled-in-burlap nursery sack.
Root Collar – The junction between the root of a plant and its stem, often indicated by the trunk flare.
Root Crown – Same as Root Collar.
Root Hairs – A hairlike tubular outgrowth, from near the tip of a rootlet, performing the work of absorption.

Tree Vocabulary – P


Parent Branch or Stem – The tree trunk or the larger limb from which lateral branches are growing.
Photosynthesis – The transformation, in the presence of chlorophyll and light, of carbon dioxide (from air) and water (primarily from soil) into a simple carbohydrate and oxygen.
Permanent Branches (Permanent Limbs) – Branches that will remain on the tree for many years, perhaps throughout their lives.
Permanent Wilting Point (PWP) – Amount of water in the soil when a plant wilts and will not recover unless water is added. Contrast with wilting point.
Photosynthesis – The process that converts light energy, carbon dioxide and water into chemical energy and oxygen in green plants.
Phytotoxic – Poisonous to plants
Pollard – Pruning technique by which young trees or branches are initially headed and then re-headed on an annual basis without disturbing the callus knob.
Primary Root Plate –A radial distance from the base of the tree equal to three times the tree diameter (DBH). This represents the critical area where root cutting will compromise the structural stability of the tree. Whenever healthy trees fail due to extreme soil saturation and/or high gusting winds, the root plate is generally visible rootball, where the roots fail.

Tree Vocabulary – N


Notch-Stress – Location along a tree stem where the uniform force flow is interrupted. The result is localized, high stress areas with a greater potential for failure.
Nutrients – The substances, such as mineral elements and compounds, including water and air, that a plant synthesizes into the complex compounds of tissue.

Tree Vocabulary – M


Macronutrient – A chemical element necessary in large amounts (usually 50 mg/kg in the plant) for the growth of plants. Includes C, H, O, N, P, K, Ca, Mg and S. Contrast with micronutrient.
Mature Trees – Trees that have reached at least 75% of their typical final height and spread.
Meristem – Embryonic or undifferentiated tissue, capable of active cell division and differentiation into specialized tissues.
Micro-nutrient – A chemical element necessary in only extremely small amounts (less than 50mg/kg in the plant) for the growth of plants. Examples include B, Cl, Cu, Fe, Mn, Zn and Ni. Contrast with macronutrient.
Mulch – Any material such as stray, sawdust, leaves, plastic film,, and loose soil that is spread on the surface of the soil to protect the soil and plant roots from the effects of raindrops, soil crusting, freezing, and evaporation
Mycorrhizae – Beneficial fungi that provide water and nutrients to roots and receive carbohydrates from roots.

Tree Vocabulary – L


Lateral – A branch or twig growing from a parent branch or stem in a horizontal direction from the parent stem.
Leader – A dominant upright stem, usually the main trunk.
Lean – Departure from the vertical of the stem, beginning at or near the base of the trunk.
Limb – Same as branch, but usually larger and more prominent.
Lion Tailing – The improper practice of removing all or most secondary and tertiary branches from the interior portion of the crown, leaving most live foliage at the edge of the canopy.
Live Crown Ratio – The relative proportion of green crown to overall tree height. Live crown ratio is the ratio of percentage of foliage compared to a tree of the same species with a full crown.
Loam – A soil texture classification having less than half as much clay as sand or silt and that combines the desirable attributes of each particle size; considered the ideal soil texture for most plants.

Tree Vocabulary – I


Included Bark or Embedded Bark (EB) – Included bark occurs when bark is included into the attachment between two stems, preventing the joining of wood tissue in the area between the stems. Included bark attachments always have an extremely narrow angle between the stems, resembling the letter “V” (rather than the letter “U” or “L” typical in strong attachments). As stems having included bark increase in size, pressure is exerted from the stem expansion and a crack often develops in the crotch between the stems. Included bark attachments have a higher potential for failure in later years.
Infiltration Rate – A soil characteristic determining or describing the maximum rate at which water can enter the soil under specified conditions, including the presence of an excess of water.
Interface (Soil) – Zone between two different textures on modified and unmodified portions of a soil.
Interior Foliage – Typically small-diameter (less than 3 inches) branches with foliage on the interior or inner portion of the crown


Tree Vocabulary – H


Hardscape – The pavement, irrigation system, and other structural elements of a landscape.
Heading Cut – Pruning a currently growing of one-year shoot back to a bud, or cutting an older branch or stem back to a stub or lateral branch not sufficiently large enough to assume the terminal role.
Heart Rot – Decay present in the heartwood (center) of a tree.
Heartwood – Darker-colored wood toward the center of a stem or root that has become physiologically inactive. It no longer functions for the transport of water and nutrients, but may be a site for storage.
Herbicide – A chemical that kills plants or inhibits their growth, intended for weed control.
Host – A tree that harbors an insect or disease.
Hydraulic Soil Evacuation – A process by which high pressure and high volume water stream is used to dislodge soil around roots and a large truck-mounted vacuum unit is used to remove the slurry.