Tree Industry Definitions


A.N.S.I. – American National Standards Institute – publishes standards for various industries in the United States including the tree care industry. The standards are updated approximately every five years. The ANSI A-300 includes guidelines for pruning both young and mature trees. The standards provide guidelines for the correct techniques in pruning but are not actual specifications for how the tree should be pruned. The arborist should provide specifications on what pruning will be performed.


Arboriculture – The science that studies the comprehensive care of trees. Arboriculture covers a spectrum of tree related disciplines and integrates sciences such as forestry, soil chemistry, horticulture, botany, plant pathology and entomology. Arboriculture also focuses heavily on the physical aspects of treecare (pruning, removal, cabling & bracing etc.) and safety issues relating to tree care. Much research in the field of Arboriculture relates to understanding how a tree functions in the context of an urban environment and the needs for holistic treecare.


Cabling and bracing – The installation of hardware such as steel rods and cables into trees that are structurally weak for the purpose of strengthening the tree and prolonging its life.


Caliper – The measurement of the diameter of a tree’s trunk.


Certified Arborist – A person who has met the criteria and passed the exam and has been certified as an arborist by the International Society of Arboriculture.


Cholorosis – A condition that affects a tree’s ability to manufacture the green pigment chlorophyll and causes the tree’s foliage to yellow.


Codominant stem/included bark – A codominant stem occurs when two or more stems of essentially the same diameter emanate from the same location in the tree. If there is no branch bark ridge between the stems the bark is included. Codominant stems with included bark are structurally weak and can fail. If the codominant stems are large their failure can cause serious property damage or personal injury.


Conifer – A group of trees that bear “naked” seeds and are classified as gymnosperms. They are typically evergreen and have needle like foliage. Examples include pine, cedar, spruce, fir, juniper, redwoods and cypress (the native bald cypress is one of the few deciduous conifers). They are also referred to as softwoods, even though many of the conifer species actually have hard wood.


Conk – See definition for sporophore below.


Cycad – Cycads are a very ancient order of plants classified as gymnosperms. Their appearance is similar to palms and ferns.


DBH – The measurement in diameter inches of a tree’s trunk measured 4.5″ above grade.


Deciduous – A tree species that sheds its leaves annually and experiences a dormant period. Deciduous trees typically appear bare in the winter months. Examples of deciduous trees include maple, sycamore, hickory, elm, sweetgum, bald cypress and many oak species.


Dieback – When a tree branch dies back from the tip leaving deadwood.


Exotic tree – A non-native tree species introduced into an area from another area. Exotic trees that reproduce in an area are said to be “naturalized”.


Groundcover – Plant material that grows close to and covers the ground beneath trees and shrubs.


Hardwood tree – A group of trees that produce seeds enclosed within an ovary and are classified in taxonomy as angiosperms. More specifically they are classified as dicotyledons, a division of the angiosperms. They are also called the flowering trees of the world as they produce true flowers. Many species of this group have wood that is not actually hard. Some hardwood tree species include oak, hickory, dogwood, magnolia, maple, birch, beech, sycamore, buckeye, sweet gum, citrus, tupelo, jacaranda, etc.


Hardiness – Plant hardiness refers to a plants ability to survive low temperatures. The lower the temperature a plant can survive the greater its hardiness. The Arnold Arboretum provides a hardiness zone map of the United States and Canada that provides the low temperature extremes for all areas. Reference books on plant species provide information on the zones a particular plant is hardy in.


Hazard tree – A tree that in the judgment of a qualified arborist is deemed to possess a hazard as it is in imminent danger of falling or it has significant potential to cause personal injury or property damage.


International Society of Arboriculture (ISA) – An international organization that supports research, administers certification programs and provides numerous educational opportunities in the broad field of arboriculture.


Galls – Swollen plant tissues usually caused by the actions of insects such as wasps or sometimes by fungi or bacteria.


Grades and Standards – A set of standards for landscape plants established by the State of Florida’s Division of Plant Industry.


Lightning protection – The installation of hardware into a tree for the purpose of directing the electrical charge in lightning away from the tree and into the ground.


Macronutrient – Macronutrients are essential elements that are required in large amounts in trees. Macronutrients include nitrogen, phosphorus, potassium, calcium, magnesium and sulphur.


Mangrove – Aquatic hardwood tree species that grow in salt water environments along bay shorelines, tidal creeks and estuaries. Three species of mangroves common to Tampa Bay include red mangrove (Rhizophora mangle) black mangrove (Avicennia germinans) and white mangrove (Laguncularia racemosa). Mangroves provide numerous benefits to the ecology of salt water environments and are among the most valuable plants in the world. Consequently, they are protected by State of Florida statutes.


Micronutrient – Micronutrients are essential elements that are required in smaller quantities than the macronutrients however, a deficiency of a micronutrient can disrupt tree health and cause decline. Micronutrients include boron, chlorine, copper, iron, manganese, molybdenum and zinc.


Mistletoe – Mistletoe (Phoradendron flavescens), is a plant parasite that infests a number of tree species.


Moss – Two common moss plants that are found on trees in our area are ball moss (Tillandsia recurvata) and Spanish moss (Tillandsia usneoides). These plants are not true mosses but are actually bromeliads. They are classified as an epiphyte because they take nutrients from the surrounding air.


Mychorhizae – Mychorhizae is a beneficial fungus that is in a symbiotic relationship with the tree and colonizes on tree roots and helps with the absorption of nutrients.


Native tree – A tree species that existed in North America prior to European invasion.


Naturalized tree – An exotic tree that is able to reproduce in an area and establish a population.


Nutrient – There are 16 nutrients or essential elements required by trees for growth and reproduction. Three nutrients, hydrogen, oxygen and carbon are obtained from the water and air. Macronutrients (required in large amounts by plants) include nitrogen, phosphorus, potassium, sulphur, magnesium and calcium. Micronutrients (required in smaller amounts) include iron, copper, manganese, zinc, copper, boron, chlorine and molybdenum. Macronutrients and micronutrients are both important to trees and a deficiency of any nutrient can lead to tree decline.


Nutrient cycling – The practice of allowing dead or dying plant parts to decay naturally back into the soil. A good example is allowing leaves that shed in the fall to remain on the ground and decompose as opposed to raking them up and placing them into a garbage can. Nutrient cycling helps the soil maintain fertility.


Palm – A palm is not a true tree but is a plant that belongs to the group of plants classified as monocots. Monocots are a subdivision of angiosperms. Palms are closely related to lilies, irises and grasses. Palm trees do not produce lignin and cellulose the building blocks of wood, consequently they do not produce annual growth rings and experience an increase of trunk diameter as they age.


pH – pH is the measure of the acidity of alkalinity of soil or water.


Pruning – The arboricultural practice of removing branches from trees. Trees are pruned to remove deadwood or dying branches, improve appearance, help make trees compatible to adjacent structures, improve the structure of trees by removing weak branches. Every pruning cut should have a purpose and be performed by a professional who understands the consequences of the pruning.


Root pruning – The practice of severing roots using equipment designed for that purpose. Roots that are causing damage to structures are pruned and roots that will be impacted by excavation activities may be pruned to reduce the damage inflicted by heavy equipment.


Scaffold branches – The very large diameter branches in a tree’s crown.


Species – The species is the level of plant classification that identifies a specific type of plant. For instance, calling a tree an oak tree can mean several different types of trees, e.g., live oak, laurel oak, water oak, turkey oak, bluejack oak, etc. But calling a tree a live oak is specific. However, live oak is a common name and to correctly identify a plant species you should use its botanical name as well. The botanical name is a two part name or binomial. The binomial is in Latin and includes the genus and species. The genus and species are italicized. Thus the botanical name for live oak is Quercus virginiana. The genus is capitalized but not the species.


Sporophore – The fruiting body of a fungus also called a conk. A sporophore comes in many shapes, sizes and colors.


Subordinate pruning – A type of pruning that removes or reduces codominant branches until the tree has a strong central leader.


Structure – Tree structure refers to how the branches form the framework of a tree and relates to the size and spacing of branches relative to the trunk. The trunk supports branches and branches support twigs and twigs support leaves. Some trees have multiple trunks. Large branches that support a large portion of the crown are often called leaders or scaffold branches. Some trees have good structure and will endure high winds without experiencing significant branch failure while other trees have weak structure and will be prone to branch failure.


Tree – A tree is a self-supporting woody perennial plant with a single trunk that is capable of obtaining a large size. Many species such as crape myrtle develop multiple trunks but are still considered trees. Palms are not trees.


Tree ordinance – A local ordinance that provides the criteria relative to tree preservation and regulates activities performed on trees.


Vascular system – The vessels in a tree with the function of transporting material within the tree. The two primary vascular tissues are the phloem which transports the food produced during photosynthesis throughout the tree and the xylem which transports water and nutrients absorbed by the roots to the leaves for use during the photosynthesis process.