Identifying Different Types of Leaves
Ever wonder how you might break down the different types of leaves for analysis? You’ve no doubt already noticed there is a big difference between a cactus, a redwood, and a palm. Even among the typical sorts of growths we normally think of when we think about trees, there are several variations.
Here’s a break down:
The Stems of Different Types of Leaves
Petiolated: Botanists call leaves with stems, or more accurately petioles, petiolated leaves.
Sessile: Leaves without these short stems/petioles are sessile leaves. They come directly from the branch without a bridging stem.
Simple versus Compound Types of Leaves
Simple Leaves: Simple leaves extend outward in one unified shape. If you look carefully at a leaf, holding it in your hand, you will see that just like us, it has veins. In a simple leaf, the central artery goes straight up into the blade of the leaf.
Compound Leaves: Compound leaves resemble separate leaves that nature has fused together. The central arteries separate into individuated paths typically near the base of the leaf, perhaps just as it comes off the petiole. They are all clearly one organism, but they seem to have several distinct leaf-like sections. Botanists call these distinct subsections, leaflets.
Shapes of Different Types of Leaves
Botanists further divide leaves into seven shapes:
Ovate: Coming from the Latin word for “egg,” ovate leaves are exactly as they sound, shaped like eggs, with out sharp end points.
Cordate: Coming from the Latin word for “heart,” these are also what they sound like, heart-shaped leaves, wider at the base but unlike ovate leaves drawing to points at the apexes.
Lanceolate: As you might guess without any knowledge of Latin, nature has shaped these leaves somewhat like spears—or more accurately “lances.” You might think of them as cordate leaves on a diet since they only differ according to the relative width at the base.
Elliptic: Similarly, elliptic leaves are just thin ovate leaves. They end in curved rather than pointed edges but they are much more long than wide.
Hastate: Hastate leaves look like three connected leaves stretching out from a central point. This compound leaf shape looks exactly like the medieval weapon known as the halberd. You might have seen this weapon if you watch old movies with knights in them. This half-axe, half-spear is the weapon that the palace guards always seem to sport as the hero of the tale dispatches them.
Acicular: Acicular leaves are long needle-like leaves ending in pointed tips. The kind you might find on a pine tree.
Linear: Finally, there are linear leaves that are just acicular leaves with rounded ends.
Edges of Different Types of Leaves
Botanists also identify leaves by five different kinds of edges.
Entire: Leaves with entire edges are simply those with smooth edges, as if nature’s artist drew them in motion.
Sinuate: Sinuate leaves have waves or bumps along their curved edges.
Dentate: Coming from the Latin word for “teeth,” dentate leaves have little teeth or hook like protrusions at intervals along the leaf’s edge.
Serrate: Similar to dentate leaves, serrate leaves have tooth like protrusions as well, but they are so close to each other that they seem more like the teeth of a saw.
Lobed: Lobed leaves have, you guessed it, lobes that stick out from the leaf at strange intervals.
The Uses of the Descriptive Language
Now that you have these language tools under your belt, you will no longer be at a loss when describing a leaf. You will be able to say, “Today I saw a petiolated compound leaf with serrated lanceolate leaflets.” Of course, only botanists will really know what you are talking about, but at least you now have ways of knowing exactly what you are looking at when you look at these beautiful works of natural art.