Ohio Trees Index

Glossary of Terms The more we learn about trees, the more our enjoyment and appreciation for them grows.
Term	Description

alternate	The arrangement of leaves along a stem where consecutive leaves alternate along different sides of the stem. Taken together, all of the leaves plus the stem lie in roughly the same geometric plane. In winter (after leaf drop for deciduous plants), the arrangement can be determined by looking at the leaf scars or buds on the dormant twigs.
auricle	A small leaflike structure (often seen as a pair of auricles) that occurs at the base of the new flush of shoot growth, and which may or may not persist throughout the growing season. The prime example is the blue-green auricles of Blackhaw.
axil	The area between a leaf and stem, where an axillary bud forms. The axillary bud can be a floral bud that becomes a flower, or a vegetative bud that may produce a lateral stem (or remain dormant).
bipinnately compound	The situation where a compound leaf has its leaflets attached to a rachilla, and rachillae attach to a primary rachis, which then attaches to the true stem of the plant. Kentucky Coffeetree and some leaves of Honeylocust are good examples of bipinnately compound leaves.
bud	The tightly wrapped structure that contains miniaturized forms of leaves and stems (vegetative bud) which may open at a later date or remain dormant forever, or flowers (floral bud) which open the following spring.
bundle	The grouping together of needles on a pine tree into a unified cluster, bound by a sheath (or fascicle) at the base, and attached at a single point to the twig. Individual species of pine trees are known by the number of needles in a bundle; for example, White Pine has five, Loblolly Pine has three, and Scotch Pine has two.
candle	The newly emergent growth of needles and shoots at the branch tip of a pine tree, usually having a white or white-green color.
canopy	The portion of the tree that contains the branches, especially the upper branches.
catkin	A cluster of long male flowers without petals (typical of the oaks, hickories, walnuts, birches, and other trees) that hangs from a twig in spring and serves to pollinate the separate female flowers.
chartreuse	The green-yellow color that is common among trees that have poor fall coloration of their foliage.
conifer	A plant that has cones, rather than fruits, as its method of dispersing seeds. Most conifers are needle-foliaged (evergreens such as the Spruces and Pines, or deciduous versions such as Larch) that have relatively large cones that spread open at maturity. However, others have a miniature berry-like cone (such as the Junipers) or a ball-like cone (such as Baldcypress, a deciduous conifer) instead.
crenate	The condition where the margins of a leaf (or leaflet) have relatively large rounded projections, but not so large as to be considered lobes. Swamp White Oak is a good example of a tree with leaves that have crenate margins.
deciduous	The condition where the margins of a leaf (or leaflet) have relatively large jagged projections, but not so large as to be considered lobes. Arrowwood Viburnum is a good example of a shrub with leaves having dentate margins.
dioecious	Plants that have male flowers (or staminate flowers) on one plant, and female flowers (or pistillate flowers) on another plant. Therefore, a pollinating male plant bears no fruits or seeds, whereas a female plant may have fruits, if pollination and favorable environmental conditions occur. Examples of dioecious trees include Green Ash and Osage Orange. An advantage of dioecious trees is that seedless males can be selected and propagated.
elliptical	The condition where the shape of a leaf or leaflet is widest at the middle.
evergreen	A woody plant that retains its leaves throughout the winter. These include broad-leaved evergreens (such as most rhododendrons and bayberries) and the more common needle evergreens (the pines, spruces, firs, and hemlocks).
floral bud	A bud that develops into a flower the following year. Although often occurring as a lateral bud, it can also be a terminal bud (as in European Horsechestnut) or even on the bark of trunks (as in Redbud).
fruit	The reproductive structure that includes the inner seeds. Mature fruits can be moist (such as the fleshy fruit of Pawpaw), mealy (such as the nuts of the Hickories), or dry (such as the wafers of the Elms).
growth rate	The amount which the uppermost twigs of a woody plant grow in one year; specifically, a slow growth rate is 1 foot or less per year, a medium growth rate is 1 to 2 feet per year, and a rapid growth rate is greater than two feet per year.
hardiness zone	A geographic area that contains a set range of average minimum winter temperatures. From the USDA map, southern Ohio is generally zone 6 (range of 0 to -10 degrees Fahrenheit minimum temperature in a given year), and northern Ohio is generally zone 5 (range of -10 to -20 degrees Fahrenheit minimum temperature in a given year). A given plant is at the northern limit of its range when it encounters its winter hardiness zone temperature. In recent years, winters have generally been much warmer than average.
hardwood	A term used in reference to the relative hardness of wood in a tree. Examples of hardwoods include the oaks, hickories, and ashes.
irregular	A growth habit that is not of a particular shape, often assumed as trees grow old and lose their characteristic form due to natural spreading of the canopy, and sometimes with the additional impact of storm damage.
lateral bud	A bud that originates just above the point of leaf attachment to the stem. A lateral bud may be a floral bud that flowers the following year, or a vegetative bud that can potentially become a lateral stem.
leaf scar	The scarred portion of a twig where a leaf once attached. After several years, the enlarging twig becomes a branch, and the bark of the branch overwhelms the leaf scars, rendering them non-existent
leaflet	In compound leaves such as the ashes, the green blades that attach to the central rachis are termed leaflets (a simple leaf like Redbud, on the other hand, does not have leaflets, but instead has only a single leaf blade attached to a petiole).
lenticel	A small opening (either a pore or a slit) in the bark of the tree, through which the tree "breathes" air into the cambium and other living tissues of the outer trunk. While all trees have lenticels, some are more easily observed on twigs and young branches (such as those of Black Cherry and River Birch) than others.
monoecious	Plants that have male flowers (or staminate flowers) and female flowers (or pistillate flowers) on the same plant. Therefore, a monoecious plant will bear fruit from some of the female flowers scattered throughout its growth, if favorable environmental conditions occur. Examples of monoecious trees include American Beech and Black Walnut.
node	The place along a stem or twig where a structure (such as a leaf, leaf scar, or lateral bud) is attached. Nodes may have single structures (alternate arrangement), dual structures (opposite arrangement), or multiple structures (whorled arrangement). Usually, the apex of a twig is considered the terminal node. The areas of a twig between the nodes are called the internodes, and constitute the overwhelming majority of the twig.
oblong	The condition where the shape of a leaf or leaflet is widest for a good length of the leaf along the middle, where both sides of the leaf are roughly parallel for a majority of the leaf blade, such as in Shingle Oak or Blue Beech.
obovate	The condition where the shape of a leaf or leaflet is widest above the middle (that is, closer to the apex [or tip] of the leaf), such as the leaflets of Common Horsechestnut.
opposite	The arrangement of leaves along a stem where a pair of leaves are opposite one another, with the stem in-between. Taken together, all of the leaves plus the stem lie in roughly the same geometric plane. In winter (after leaf drop for deciduous plants), the arrangement can be determined by looking at the leaf scars or buds on the dormant twigs.
ovate	The condition where the shape of a leaf or leaflet is widest below the middle (that is, closer to the top of the petiole).
palmately compound	The arrangement of leaflets in whorled fashion around the top of the petiole, which then attaches to the stem of the plant. This resembles the arrangement of fingers attached to the palm of a hand, which itself attaches to the arm (at the wrist). Ohio Buckeye and European Horsechestnut are good examples of palmately compound leaves.
pedicel	The stem-like structure that attaches a developing flower (or fruit) to the twig (or peduncle, which then attaches to the twig).
perfect flower	A flower that has both male and female parts in the same structure, and can therefore give rise to a fruit under appropriate environmental conditions. Plants with perfect flowers do not have separate male and female trees. Perfect flowers that have both petals and sepals are called complete flowers.
petals	The showy structures for most flowers. In a single flower, all of the petals taken together as a unit are called the corolla.
petiole	In a simple leaf, the petiole is the structure that attaches the leaf blade to the stem. In a palmately compound leaf, the petiole attaches the leaflets to the stem. In a pinnately compound leaf, the petiole attaches the leaflets to the rachis, which in turn attaches to the stem.
pH	The amount of active acidity contained within a solution (such as the moisture in soil), expressed on a logarithmic scale. Numbers decreasing from 7.0 represent more acidic (or sour) conditions, numbers increasing from 7.0 represent more alkaline (or sweet) conditions, and 7.0 represents a neutral condition. Many soils in eastern Ohio are slightly acidic, while many soils in western Ohio are slightly alkaline.
pinnately compound leaf	The situation where a leaf is not simple, but rather composed of leaflets attached to a central rachis, which then attaches to the true twig of the plant. In autumn for woody plants, the leaflets detach from the rachis, and the rachis falls off from the twig, completing leaf drop. Black Locust and White Ash are good examples of pinnately compound leaves.
polygamo-dioecious	A species that has male flowers and female flowers on separate plants, but each of these types of plants has perfect flowers as well. Therefore, all plants of a polygamodioecious species may bear fruit under appropriate environmental conditions, but some plants may have many more fruits than others. Examples of this rare floral assemblage include Honeylocust.
polygamo-monoecious	A species that has male flowers and female flowers on the same plant, plus some perfect flowers as well. Therefore, all plants of a polygamo-monoecious species may bear fruit under appropriate environmental conditions. Hackberry is an example of this type of rare floral assemblage.
pubescence	The fuzziness found on some leaves, stems, buds, floral structures, and fruits, especially when they are immature.
rachilla	In a bipinnately compound leaf, the elongated structure that attaches to both the leaflets and the central rachis. Several rachilla attach to the rachis in a bipinnately compound leaf, the best examples of which are Honeylocust and Kentucky Coffeetree.
rachis	In a pinnately compound leaf, the elongated structure that attaches to both the leaflets and the petiole, which then attaches to the stem. A rachis is sometimes referred to as the axis of the pinnately compound leaf.
samara	A type of dried fruit that has a seed attached to a wing, which often causes the fruit to spin downward when it falls from a tree. Most Maples have paired samaras in clusters, while most Ashes and Tree-of-Heaven have single samaras in large clusters.
sepals	The petal-like structures just below the petals in some flowers. Sepals may be the same or different color, the same or different size, and in the same plane or held reflexed, as compared to the petals. In a single flower, all of the sepals taken together as a unit are called the calyx. The corolla and calyx taken together are called the perianth.
serrate	The condition where the margins of a leaf (or leaflet) have small jagged projections; examples include the leaves of Hackberry. A doubly serrated leaf has fine serrations that occur on the edges of larger serrations; an example is the leaf of American Elm. A leaf (or leaflet) that has smooth margins is called "entire", such as in Pawpaw.
simple leaf	The most common type of leaf, where a single leaf blade attaches to a petiole, which then attaches to a twig of the plant. In autumn, both the leaf blade and the petiole detach from the twig as a single unit, completing leaf abscission.
softwood	A term used in reference to the relative softness of the wood in a tree. Examples of softwoods include Colorado Spruce, and White Pine.
spiraled	The arrangement of leaves along a stem, where consecutive leaves are arranged in roughly a continuous spiral pattern along the axis of the stem All of the leaves plus the stem do not in any way lie in a geometric plane. Examples include some of the conifers, including Eastern Larch, Bald Cypress, and Colorado Spruce.
stipule	Very small, leaflike structures that occur at the base of the petiole on the leaves of a very few trees, usually appearing briefly in early spring with leaf emergence, and soon falling away. Examples include the large stipules of Tuliptree and the very small ones of some American Chestnuts.
style	In a female (pistillate) flower, or the female portion of a perfect flower, the long tube connecting the stigma (structure at the tip which collects pollen) from the ovary (basal structure deep in the flower which contains ovules that later develop into seeds.
terminal bud	A bud that occurs at the end of a stem. Although it is usually a vegetative bud that will continue the growth of the stem the following year, it can also be a floral bud that will flower the following year. Some trees do not have a true terminal bud (Tree of Heaven is a good example), in which case the uppermost lateral bud serves its purpose.
texture	The overall appearance of a plant in a given season, as determined by its individual structures. Examples of fine texture include Eastern Hemlock and Baldcypress in all seasons, while Bur Oak and Black Walnut exhibit bold texture in winter.
vegetative bud	A bud that develops into a stem with leaves, either originating as a terminal bud or as a lateral bud.
whorled	The arrangement of leaves along a stem where a cluster of three or more leaves occurs at the same juncture on the stem. In winter (after leaf drop for deciduous plants), the arrangement can be determined by looking at the leaf scars on the dormant twigs, such as in Catalpa.

Glossary of Terms

The more we learn about trees, the more our enjoyment and appreciation for them grows.