Tree Terminology

Achene A small, dry, 1-celled, 1-seeded, indehiscent fruit, the seed attached to the wall of the fruit at one place. Example: London Plane.
Acorn A type of dry fruit composed of a nut with a cap of fused bracts. Example: Oak.
Alternate Leaves one at a node, borne singly. Compare "opposite".
Axil The place where the leaf stalk (petiole) meets the stem. A dormant bud is often located in this place.
Ball and burlap Method of preparing tree for transplanting. A ball of soil is left around the roots when it is dug up. The soil and roots are wrapped in burlap or plastic to hold it together and retain moisture. Abbreviated "B&B".
Bare root Another method for transplanting. Dormant trees are dug, roots washed and trimmed, and kept moist until replanted.
Bract A modified leaf situated near a flower or inflorescence.
Branch Bark Collar The ring of tissue at the place where a branch is attached to the trunk.
Broad leaved A tree with broad leaves rather than needle-like leaves. Examples: Maple, Oak, Elm.
Bud The rudimentary stage of development of a branch, leaf, or flower.
Caliper The diameter of a tree's trunk, as measured by nurseries, at 6 inches above the planting line.
Callus Scar tissue formed around cut wounds, eventually covering them. Formation of callus is greatly aided by a smoothly finished pruning cut.
Catkin (Ament) A tassel-like pendulous inflorescence bearing many unisexual flowers. Oak, Birch, Willow, and Poplar are catkin-bearing.
Columnar Describes a narrow upright tree form. See fastigiate.
Compaction Used in reference to soil. Soil becomes hardened and compressed making it difficult for roots to penetrate the soil. Air chambers in between soil particles are also greatly reduced or are nonexistent, making drainage and gas exchange from roots poor.
Compound A leaf that is composed of two or more leaflets, arranged in a pinnate or palmate pattern. Compare "simple".
Conifer A deciduous or evergreen tree bearing cones rather than true flowers. Examples: Pine, Spruce, Larch, Fir. Foliage is needle-like.
Deciduous A tree which drops its foliage at the end of the growing season and develops new foliage the next spring. Not synonymous with broadleaved tree - some conifers (examples: Larch, Dawn Redwood, Bald Cypress) drop their needles each fall.
Dehiscent Splitting open; method of dispersing contents usually of anthers or seed pods by splitting open along defined slits.
Drupe A type of fruit that has a fleshy exterior with a large pit inside (examples, Japanese Zelkova as well as Cherry, Peach, Plum, and Apricot).
Entire Refers to a type of leaf margin or edge, where the edge is smooth, with no teeth or lobes.
Evergreen A tree which retains its foliage throughout the year. Not synonymous with conifer - some broadleaved trees (examples: American Holly, Southern Magnolia, Live Oak) are evergreen.
Exfoliating Bark that peels off in thin layers. Example; London Plane.
Flush Flat against.
Fastigiate A tall, narrow tree form with a strong central leader and branch attachments at acute angles.
Girdling The cutting, removing, or clamping of bark completely around a branch or the trunk of a tree. Can kill the branch or the entire tree.
Glabrous Devoid of hairs; smooth.
Grafting A method of inserting a shoot or bud taken from one plant into the stem or branch of another so that the shoot or bud grows and becomes a permanent part of the other plant.
Guy Wire A wire used with support stakes to help support a newly planted tree.
Hardpan Describes a soil condition of extreme compaction; compaction in layers.
Humus Decomposed organic matter. When added to any soil, humus increases the soil water-and nutrient-holding capacity, porosity, and tilth (particle structure).
Indehiscent Not opening by definite lines or pores. Compare "dehiscent".
Inflorescence The flowering part of a plant; specifically, the arrangement of a flower cluster.
Examples: catkin, spike, raceme.
Leader The central stem or trunk that is longer and more vigorous than the side branches or lateral stems.
Leaf A plant organ whose function in general is to conduct photosynthesis. Usually composed of a stalk (petiole) and a broad portion (blade). In general, a leaf has a bud at its base. Compare "leaflet".
Leaflet The leaf-like division of a compound leaf. Unlike a leaf, a leaflet does not have a bud at its point of attachment (axil).
Legume The characteristic fruit of the Leguminosae family consisting of a long pod containing large seeds lined up one by one. Examples: Honey Locust, Chinese Scholar Tree.
Lenticel Small corky-celled structures on the surface of twigs and branches, and/or trunk of some species, whose function is to allow the transport of gases to and from the inner tissues.
Lobe A segment of the blade of a leaf. Example: The leaf of a Norway Maple is palmately-lobed. Compare "sinus".
Loment A leguminous fruit that is characterized by narrow constrictions in the spaces between the seeds. Example: The fruit of the Chinese Scholar Tree.
Margin The edge of a leaf.
Monoculture A population of trees comprised mostly of one species or variety.
Mulch Any material laid on the soil surface to conserve soil moisture, moderate temperature and/or aid in weed control. Wood chips, bark chips, and shredded leaves are examples of organic mulches.
Node The place on a stem where leaves or branches originate.
Opposite Leaves two at a node and positioned across the stem from each other. Compare "alternate".
Palmate A type of leaf whose lobes or segments attach to the stalk (petiole) at one point. Examples: Horsechestnut, Maple. Compare "pinnate".
Panicle A type of compound inflorescence where the flowers are attached to a multi-branched stem and the youngest flowers are at the apex or center.
Petiole The stalk of a leaf blade or compound leaf. It can range from very long to completely absent. A petiolule is the stalk of a leaflet.
Pinnate A type of compound leaf with leaflets on two opposites sides of an elongated rachis. Examples: Ash, Chinese Scholar Tree.
Pome A multi-celled, multi-seeded, fleshy, indehiscent fruit. Examples: Callery Pear, Apple.
Pubescent Covered with hairs; hairy.
Raceme An inflorescence where the flowers are attached to an elongated rachis and the youngest flowers are at the apex.
Rachis The central elongated axis of an inflorescence or compound leaf.
Samara A dry fruit composed of a seed with a papery wing attached. Examples: Maple, Ash, Elm.
Serrate A type of leaf margin which has sharp teeth that are angled forward towards the apex of the leaf blade. Compare "entire".
Scion The bud or shoot which will become the top of a grafted plant.
Simple A type of leaf which is comprised of only one part and not completely divided into separate segments. Compare "compound".
Sinus The depression or indentation between two adjoining lobes. Compare "lobe".
Stock The root, trunk, or branch base used for grafting.
Stub Cut Also called a 3-part cut. Pruning method used to remove a limb without damaging the bark on trunk below the limb being removed.
Sucker A shoot or stem that originates from the roots.
Tree Wound Dressing A petroleum-based product used to cover freshly cut wood to inhibit decay or insect infestation. Current research suggests that the chemicals in these products may inhibit callus formation and therefore slow the closing of the wound. Its use is not recommended on most small wounds.
Umbel A convex or flat-topped inflorescence where the flowers are attached at one point and the youngest flowers are in the center.
Watersprout Vigorous shoot, originating above the ground, from the trunk or main branches.
Weedy The condition where a plant produces abundant seeds which germinate freely in places where they are unwanted.