Plant Glossary

Glossary of Plant Terms

Starting with the letter: (Click on letter to open/close the definitions.)
A	B	C	D	E	F	G	H	I	L	M	N	O	P	Q	R	S	T	U	V	W	X
acuminate Tapering concavely to a point. acute Tapering with straight or slightly convex sides to a point. anther The free end of the stamen that bears pollen; pollen sac. apex Tip of a leaf or flower. apiculate Having a short, sharp point. axillary The angle between the stem and leaf. azalea Azaleas are found in subgenera Pentanthera and Tsutsusi of genus Rhododendron. These subgenera are commonly referred to as deciduous and evergreen, respectively. Azalea leaves are typically thin, flexible while leaves elsewhere in the genus tend to be leathery. Deciduous azaleas are so called because they drop their leaves in the fall or winter. Evergreen azaleas have two kinds of leaves: spring leaves emerge at or after time of flowering; summer leaves (usually smaller and somewhat thicker) emerge midsummer and remain on the plant through the winter. Another important difference is that the terminal buds of deciduous azaleas produce only flowers; those of evergreen azaleas produce new vegetative shoots as well as flowers.
basal Pertaining to or at the base. bi-generic Hybrid with parents in two different genera. blade Extended portion of a leaf. blotch Area of contrasting color on the uppermost petal(s) of some plants. (See also spotting.) bract A modified leaf or bud covering. bristle A slender, stiff hair. bullate Puckered or quilted appearance.
calyx Outer whorl of floral envelopes, composed of sepals. campanulate Bell-shaped, cup-shaped. capsule Seed pod. cilia Small hairs, often present on leaf margins. clone A genetically identical plant resulting from asexual propagation (cuttings, layering, grafting, or tissue culture). conic Cone shaped, conical. convex Curved outward. cordate Heart-shaped, two rounded basal lobes separated by a deep depression. coriaceous Leathery in texture. corolla The floral envelope inside the calyx, composed of a whorl of petals. cultivar Shortened form of cultivated variety. A group of plants, selected for particular attributes, that are clearly distinct, uniform, and stable and that retain these characteristics when propagated by appropriate means. cuneate Wedge-shaped acute angle at the leaf base. cutting New growth cut for rooting or other vegetative propagation.
deadheading Removal of flower clusters after they have begun to fade. Done right after blooming and before the branching shoots begin to grow. deciduous Shedding their leaves at the end of the growing season. declinate Bent or curved downward or forward. deflexed Bent abruptly downward. dorsal Pertaining to the upper portion of a flower or leaf. double Having more than one set of petals or petal-like structures, or with petaloid stamens.
elepidote Without scales, as opposed to lepidote (with scales). elliptic Oblong with rounded ends. endemic Native or confined naturally to a given geographical area. epiphyte A plant growing non-parasitically upon another. ericaceous Belong to the family Ericaceae, which includes rhododendrons, heathers, mountain laurel, blueberries, etc. evergreen Bearing green foliage throughout the year. exserted projecting beyond, such as stamens projecting from the corolla
family A group of genera sharing certain characteristics. feral Wild or escaped from domestication and able to reproduce normally. filament The thread-like stalk of a stamen. floccuose Having tufts of soft hair or wool. flower The specialized reproductive structure of a seed plant. Rhododendrons have flowers, not florets. form, pl. formae A minor variation within a species that is sufficiently distinctive to warrant recognition as a separate taxon. In cultivated plants, it is current practice to name these forms as cultivars.
genus, pl. genera. A taxonomic group comprising closely related species. glabrous Hairless glaucous Having a gray or whitish cast, covered with a bluish, gray, or white bloom. globose Nearly spherical. grex All the seedlings of a particular cross.
habit General form of a plant. hardiness Cold hardiness is the lowest temperature a plant can tolerate without damage. hirsute With rough or coarse, more or less, erect hairs. hose-in-hose A double flower having floral envelopes (whorls of petals or petal-like structures) nested one within the other. The term relates only to appearance, not to the morphology of the structures. hybrid Usually a cross between different clones within a species (intraspecific hybrid) or between clones from different species.
indumentum A wooly or hairy covering of leaves or young shoots. Can be on both top and bottom surfaces of new or young leaves, but is usually confined to the underside of mature leaves. inflorescence An arrangement of flowers on a stem or axis, it may comprise a cluster of flowers or a single flower. involute Rolled inward or toward the upper side.
lamina Blade of a leaf. lanceolate Shaped like a lance head, widening above the base and tapering toward the apex. lax Not rigid, loose. lepidote Having scales. Tiny scales typically cover the undersides of the leaves. Characteristic used to separate the genus rhododendron into two major groups. lobe A rounded division of a flower or leaf.
margin Leaf or flower edge. mucronate Having a leaf tip terminating in a hard point that is a continuation of the midvein. mutation An inheritable change in genetic material.
nectary Nectar secreting gland at the base of the corolla. nervate Leaves with prominent ribs or veins.
obovate Egg-shaped with the broadest part towards the apex. oblanceolate Widest near apex, tapering to base, longer than wide. oblique Unequal-sided, lacking symmetry oblong Much longer than wide, with sides roughly parallel for most of their length. obtuse Blunt at the apex. orbicular Flat with the outline circular or nearly circular; disc shaped. ovate Egg-shaped with the broadest part towards the base. ovary Seed bearing part of the pistil.
pedicel The stalk of an individual flower in an inflorescence. pendulous Hanging down, drooping. petal One division of the corolla. petaloid like or consisting of petals. petiole The stack of a leaf. pH A measure of acidity or alkalinity. A pH of 7.0 is neutral. Smaller numbers indicate acidity, larger numbers indicate alkalinity. Rhododendrons, like other members of the heath family, favor soils which are mildly acidic with a pH around 5.5. pistil The female organ of a flower consisting of ovary, style and stigma. pollen Minute powder-like grains borne by the anther. Pollen contains the male gametophyte of a plant. precocious Flowering before the leaves appear. pubescent Covered with soft, short hair.
quadrate Square or nearly square.
recurved Curved backward or downward. retuse Having a rounded apex in which there is a slight notch. revolute Rolled back or downward from the margins. rhododendron Genus of shrubs in the Ericaceae family (from Greek rhodo meaning rose and dendron meaning tree). In common usage, "rhododendron" usually refers to members of the subgenera Rhododendron and Hymenanthes, as distinct from the azaleas. rotate Wheel shaped, saucer-like rugose Wrinkled. rugulose Lightly wrinkled.
section A division of classification. Sections and subsections are taxonomic groups between genus and species. scale Tiny, plate-like structures appearing on leaves and other plant parts. sepal Lower flower part, the calyx. series A category in an outdated system of rhododendron classification. sessile Without a stalk. spatulate Shaped like a spatula, spoon or paddle. species Basic classification unit of plants comprised of individuals that are recognized as distinct from other species, and which can freely interbreed among themselves. sport A naturally occurring mutation which usually appears spontaneously with characteristics which differ from the rest of the plant, such as different flower color, variegated leaves, etc. spotting Dots or spots, usually of darker color, sometimes found on the upper petal(s) of some rhododendrons and azaleas. stamen The male organ of a flower consisting of an anther on a filament. stigma The tip of the pistil, usually sticky, which receives the pollen for fertilization of the ovule. strigose Rough with straight, short sharp appressed hairs. subgenus The principal subdivision of a genus. suborbicular Not quite circular. subsection See "section".
taxonomy Classification (based on study of morphology, geographic distribution, phylogeny) and nomeclature. throat The base opening of the corolla. tomentose Covered with matted, wooly hair. tomentum Matted wooly hairs on stems, leaves or seeds. truss Flower cluster (inflorescence) made up of many individual flowers. The structure varies considerably among species and cultivars, giving the plants a distinctive appearance.
undulate Wavy
variety A naturally occurring group within a species that is distinct enough to warrant taxonomic recognition but not sufficiently distinct to be segregated as another species. vein A vascular bundle in a leaf blade or petal.
whorl Three or more leaves or branches at a node; circle of flower parts as sepals, petals or stamens. woolly Clad with long, soft more or less or matted hairs.
xylem Tissues in plants through which water and food is conveyed up the stem from the roots, also furnishing support of the plant.