Glossary of Tree Terms

acid

Having a pH level below 7.

alkaline

Having a pH level above 7.

allelopathy

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 (such 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 leaf stem. Where the leaf stem 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

A tree that shed all leaves annually.

entire

A leaf margin with smooth, untoothed edges.

evergreen

A tree 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.

native

Inherent and original to a geographic area.

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.

pH

Acidity or alkalinity ranging from 3 (strongly acid) to 11 (strongly alkaline) with 7 being neutral.

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 allow recreational activities.

riparian zone

An area of ecological transition between the aquatic zone and the upland zone (e.g., the bank of a river).

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

Fertile by means of its own pollen. This makes it theoretically possible for both pollen and ovules to unite (with the help of pollinators such as bees) and produce fruit without a second tree being present.

self-pollinating

A self-fertile specimen that does not require pollinators (such as bees) to unite the pollen and ovules.

simple leaf

A single leaf blade with a bud at the base of the leaf stem.

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.