ALLEOPATHY - The suppression of growth of one plant species by another due to the release of toxic substances.

ALTERNATE Leaves that are staggered, not placed directly across from each other on the twig.

ANTHRACNOSE A group of fungi that cause dieback and sometimes death to various species, such as dogwoods, sycamores, oaks, and maples.

BLADE The flat part of a leaf or leaflet, characteristic of broadleaf trees.

BRACT A modified leaf that bears a flower.

BROADLEAF A tree with leaves that are flat and thin, and generally shed annually.

BUD SCAR The marks remaining after bud scales drop in the spring.

CLINGSTONE Any of various stone fruits (as some peaches or plums) with flesh that adheres strongly to the pit.

COMPOUND LEAF A leaf with more than one blade. All blades are attached to a single leafstem. Where the leafstem attaches to the twig, there is a bud.

CONIFER A cone-bearing tree.

CROSS-POLLINATION Fertilization between genetically compatible trees for better fruit, often resulting in superior offspring.

CROWN The head of foliage of a tree or shrub -- this is the form or shape of the tree.

DECIDUOUS Shedding all leaves annually.

ENTIRE A leaf margin with smooth, untoothed edges.

EVERGREEN Trees with needles or leaves that remain alive and on the tree through the winter and into the next growing season.

EXFOLIATE Peeling in shreds or thin layers, as bark from a tree.

FREESTONE A fruit stone to which the flesh does not cling.

HABIT The general mode of plant growth. Used to describe the overall shape of a tree.

HARDINESS ZONE A plant can be expected to grow in the zone's temperature extremes, as determined by the lowest annual temperature. Other conditions such as moisture, soil, and wind might affect the availability of individual plants.

KNEES The tree trunk in wet conditions exhibits a broad buttress with protrusions from the roots.

LEAF SCAR The mark left on the twig where the leaf was previously attached.

LOBES Projections that shape a leaf.

MARGIN The edge of a leaf.

MIDRIB The primary rib or central vein of a leaf.

OPPOSITE Two or three leaves that are directly across from each other on the same twig.

PALMATE Blades or lobes or veins of the leaf arranged like fingers on the palm of a hand.

PERSISTENT Deciduous leaf blades that remain on the tree for more than a year.

PETIOLE The leafstalk that connects the blade(s) to the twig.

PHYTOREMEDIATION The use of trees to take up chemicals, binding some of the material in an inert form with the tree, and converting some of it to other substances, possibly even breaking it down into the normal end product of a tree's chemical
processes.

PINNATE Blades of lobes or veins of the leaf arranged like vanes of a feather.

PISTIL The seed-bearing organ of the flower. The pistil consists of an ovary, stigma, and style when present.

POLLINATION To transfer pollen from the anther of a stamen to the stigma of a pistil, resulting in fertilization. This can occur either on a single plant (self-pollination) or between different plants. Insect pollination and wind pollination are two examples of natural pollination.

REFORESTATION The planting of forested land that has been lost due to fire, logging, drought, pests, or disease to restore beauty to the landscape, provide food and habitat for wildlife, and for recreational activities.

RIPARIAN ZONE An area of ecological transition between the aquatic zone and the upland zone.

ROOTSTOCK The root upon which the scion is grafted.

SAMARA Winged fruit.

SCION The part of the tree that is grafted or budded to rootstock.

SELF-FERTILE / SELF-POLLINATING Fertile by means of its own pollen; this makes it theoretically possible for both pollen and ovules to unite and produce fruit without a second tree being present.

SIMPLE LEAF A single leaf blade with a bud at the base of the leafstem.

SINUS Indentation between lobes on a leaf.

SPECIMEN TREE A tree placed so people can gain the greatest enjoyment for the color, texture, scent, or other pleasures it provides.

SPURS Stubby, often sharp twigs.

TEETH Notches on the outer edge of a leaf.

TRIPLOID Having three sets of chromosomes rather than the usual two. As a result, the pollen is sterile.

XERISCAPE Saving water while maintaining trees and other plants in the landscape.