Glossary of Terms Relevant to the Identification
of Trees and Shrubs
alternate leaves. Only one leaf is attached to the branch at each node. Compare to opposite leaves and whorled leaves. If the leaves are alternate the leaf scars, buds and branching pattern of the tree will also be alternate.
ament. The flowers of some trees are aggregated in conspicuous structures called aments or catkins appearing much like large buds. They consist of many reduced, unisexual flowers borne close together on a common axis, with subtending scales.
armament. Any form of sharp structure on a plant, including numerous sub-categories. Although the definitions may vary slightly from one source to the next, thorns tend to be relatively large and stout with noticeably broadened bases. Some thorns may be branched. Spines are also stiff, but tend to be more slender and not conspicuously broadened at the base. Prickles are slender, but often somewhat soft and flexible. Armament does not include pubescence.
axillary bud. Buds developed along the side of a twig are known as axillary buds or lateral buds.
bud. Above each leaf scar a bud forms during the summer and autumn and persists through the winter (or potentially for several years if it remains dormant). These so-called "winter buds" contain the small beginnings of the next season's twigs and leaves and a meristematic region which will continue to permit cell division and future growth. For many species each bud has one or more protective external bud scales varying among species in size, number, shape, color, pubescence and arrangement, often resulting in a distinctive appearance. Characters of the buds are one of the most important characters for identification of woody species.
The tissues which will become next seasons flowers are included in the same buds as the leaves for some species, and in others they are borne in separate flower buds--often of a different appearance.
Within each leaf scar there are one or more bundle scars, each representing
a cross-section of vascular bundles that ran from the branch into the
petiole when the leaf was attached. The number, shape and pattern of
bundle scars can be used to help identify some species.
catkin. The flowers of some trees are aggregated in conspicuous structures called catkins or aments and appearing much like large buds. They consist of many reduced flowers borne close together on a common axis, with subtending scales.
compound leaf. A compound leaf has the blade fully divided into several "leaflets". Compare to simple leaf.
cordate. Cordate means heart-shaped, often referring to that particular style of leaf base.
end bud. Buds which terminate a twig are defined as end buds or terminal buds.
entire margin. Entire margins are smooth, without teeth. This term is most often applied to leaf margins, but also to sepals, stipules, etc.
false end bud. In some species the last bud toward the end of the twig, although appearing to be terminal, is actually the last lateral bud on a twig that failed to develop a terminal bud. This "false end bud" can be difficult to discern until the character is fully understood, and may require a good hand lens to observe clearly for some species. However, it is often a critical character for identification of tree and shrub species and should not be ignored.
fruit. In common usage the term fruit applies to a relatively small number of edible, often sweet, juicy structures such as apples, oranges or bananas. In botanical usage the term fruit applies specifically to the mature ovary of a flower, enclosing the seeds. As such it includes the fruits named above, in addition to a wide variety of structures, including nuts, the dry samaras of maples and ashes, and even some structures such as pumpkins or cucumbers that are often placed with the "vegetables" in grocery stores.
glabrous. Hairless; not pubescent.
glaucous. Covered with a white, waxy material. Glaucous coverings are usually most prominent on young growth and are often easily dislodged or worn away in age.
imbricate. A term applied to buds with more than 2 scales which overlap one another. Contrast to valvate.
internode. The portion of a stem that lies between two adjacent nodes.
lateral bud. Buds developed along the side of a twig are known as lateral buds or axillary buds.
leaf scar. After a leaf falls, a leaf scar remains on the twig at the point at which the leaf was attached. Within each leaf scar there are one or more bundle scars, each representing a cross-section of vascular bundles that ran from the branch into the petiole when the leaf was attached.
naked bud. Buds
contain the small beginnings of the next season's leaves and a meristematic
region which will continue to permit cell division and future growth
of leaves and stems. For many species each bud has one or more modified
protective, external scales varying among species
in size, number, shape, color, pubescence and arrangement. A few species
lack the outer protective scales and the small developing leaves are
therefore visible in these "naked" buds.
node. A node is not a discrete structure, but rather that portion of a stem from which one or more leaves arise (there is also an axillary bud associated with each leaf). Species with alternate leaves produce one leaf (and bud) at each node, species with opposite leaves produce two leaves (and 2 buds) at each node. Nodes may be thought of as points of origin because the leaves arise there, and if the bud develops a branch will originate there also. The space between two nodes is called an internode.
opposite leaves. Two leaves attached to the twig directly opposite one another.
pith. The central portion of a branch, formed in the first year of growth and often visibly differentiated from the surrounding wood in color and/or texture. The pith may be circular in cross-section or it may be angled or roughly star-shaped.
pinnate. A type of compound leaf for which the leaflets are attached along both sides of an elongate central axis. Compare to palmate.
palmate. A type of compound leaf in which the leaflets are attached to a common point. Compare to pinnate.
pubescent. A covering of hairs. There are many named variants of pubescence that can be useful in distinguishing plant species from one another.
simple leaf. The blade of a simple leaf is undivided, though it may be lobed. Compare to compound leaf.
spur branch. Short lateral branches in which the internodes are extremely short, bringing several leaves close together in any given year and potentially many leaf scars close together over several years.
stipule. Stipules are green, leaf-like, (often small) structures, attached to the twigs in pairs, one at each side of the base of a petiole. In some species they may fall off early in the growing season and in others they may persist essentially throughout the growing season. In either case they leave behind distinctive, though often very small, stipule scars on the twig that may provide important key characters. The shape of stipules may vary dramatically from one species to the next. Some species do not produce stipules.
stipule scar. See the definition of stipule.
terminal bud. Buds which terminate a twig are defined as terminal buds or end buds. Compare to lateral buds which develop along the side of the twig.
thorn. As distinguished from other sharp structures on plants, thorns tend to be large and stout, often noticeably broader at the base. See armament.
A term applied to buds with two identical, opposite scales lacking obvious