The subject of plant identification is vast, complex and probably extremely tedious to all but the most dedicated botanist
. Sometimes however, it helps to know a little of the terminology
used in describing the types and shapes of leaves. I will attempt it here, but by no means intend this to be a difinitive article, I'll try to keep it relatively simple.
Leaves have 2 parts, the petiole or stalk, and the leaf blade or lamina. The structure is often strengthened by a midrib and veins. Veins can be pinnate (alternating from a central midrib), palmate (where they radiate out from a single point at the base of the blade), or parallel (running lengthwise down the leaf).
Shape of leaf
- Linear - much longer than it is wide, and roughly the same width throughout
- Lanceolate - longer than it is wide but wider at the base than the tip
- Oblanceolate - like lanceolate, but tapering at the base and wider at the tip
- Oblong - roughly twice as long as broad, with near parallel sides
- Elliptic - oblong but ends narrowing
- Ovate - egg-shaped, broader at the base
- Obovate - egg-shaped, broader at the tip
- Cuneate - wedge shaped, broad at the tip
- Spatulate - spoon shaped, oblong but tapering at the base
- Needle-shaped - short, but long and pointed, as found in pines
- Awl-shaped - like those on cacti, where the spines are the true leaves
Leaf edges or margins
- Entire - smooth, even line
- Serrate - sharp, saw-like teeth pointing forward
- Dentate - toothed, but larger teeth pointing directly outwards
- Crenate - teeth are short and rounded at the tip, scalloped
- Undulate - leaf margin forms a wavy line
- Sinuate - like undulate but much more wavy
- Incised - cut into sharp, deep irregular incisions
- Lobed - deep, rounded incisions, but not extending more than half way to the centre of the leaf
- Cleft - like lobed but incisions extend beyond half way
- Deeply lobed - very deep incisions, almost to the mid-rib or base of the blade
There are two main types of leaf, simple where the blade is in one piece and compound where the blade is made of a number of leaflets.
Compound leaves are subdivided into:
- Pinnate - leaflets are arranged along the sides of a central leaf stalk, with or without an end leaflet
- Bi-pinnate - the main leaflets are again divided into secondary leaflets
- Palmate - the leaflets are arranged so that they spread out like fingers from a single point at the base of the leaf stalk.
Arrangement of leaves on stem
- Basal or rosette- all leaves come from the base of the plant
- Alternate - 1 leaf emerges at each leaf node, they are spaced alternately up the stem
- Opposite - 2 leaves emerge from each node on opposite sides of the stem
- Whorled - more than 2 leaves at a node, spaced around the stem
- Succulent - juicy, fleshy, soft, and thickened in texture.
- Scabrous - rough to the touch; texture of sandpaper.
- Coriaceous - leather-like, tough.
- Smooth, (glabrous) - surface is not hairy, rough, pubescent, or scabrous.
- Downy - covered with very short, weak, and soft hairs.
- Pubescent - hairy.
- Canescent - covered with gray or white soft hairs
- Tomentose - covered with matted, woolly hairs.
- Hirsute - pubescent with coarse, stiff hairs.
- Hispid - rough with bristles, stiff hairs, or minute spines.