Plant Identification Characteristics

Leaf parts

The leaf is the whole part that comes out from the stem.

A leaf has a petiole, blade and margin.

• The petiole is the stem that connects the blade to the stem. If the leaf has no petiole, it is sessile.
• The blade is the flat part.
• The margin is the edge of the leaf.

The apex is the tip of the leaf.

The leaf is connected to the stem at the node.

A leaf scar is visible at the node where a leaf has fallen off.

A bud is a growing point on the plant at the node.

Leaves can be simple or compound

A simple leaf is a single continuous unit for the leaf blade.

A compound leaf is one where the blade is divided so there are multiple leaflets.

Compound leaves may be pinnate, palmate or bipinnate.

Pinnate leaves have a central axis with leaflets coming off each side.

Palmate leaves have all the leaflets coming from a central point.

Bipinnate leaves have a central axis with stems coming off it and leaflets off each stem.

Leaf arrangement

Alternate means there is one leaf at each node, alternating on each side of the stem.

Opposite means there are two leaves at each node.

Whorled means there are three or more leaves coming out at a node.

Leaf venation

Parallel venation - the veins run laterally from base to apex, essentially parallel, and are connected laterally by minute, straight veinlets.

Netted or reticulate venation - veins that branch from the midrib and then subdivide into finer veinlets - like a net. May be pinnate or palmate.

Leaf shapes

There are many names - here are a few common ones:

• Lanceolate - swordlike
• Elliptical - oval
• Spatulate - rounded and wider at the apex than the base - like a spatula
• Ovate - rounded at the base coming to a point at the apex

Leaf margins

Entire - completely smooth

Serrate - small sharp teeth pointing to the apex - saw-toothed

Doubly serrate - teeth inside the teeth

Serrulate - more teeth but less long teeth - minutely serrated

Lobed - lobes on the leaf extend less than half way to the midrib - the indented portion is called the sinus

Dentate - teeth pointing outward not forward - apex of tooth is perpendicular to the margin

Leaf surfaces

Glabrous - not hairy

Pubescent - short soft hairs

Bullate - appearing blistered between the veins

Glaucous - covered with a waxy bloom that rubs off easily - often whitish

Lustrous - not as shiny as glossy but having a slight metallic gloss