Simple Leaves
Simple leaves are leaves with undivided blades, which means that each plant leaf is a single piece. The leaf blade includes the entire leaf structure except for the stem, so the blade is essentially the leafy part of the leaf. Simple leaves may have rounded, jagged, or lobed edges. Common examples of simple leaves include those found on oak and maple trees and many fruit plants, like grapes and strawberries.
Compound Leaves
Compound leaves are leaves with divided blades, with multiple leaflets attached to a vein, or central stem, that runs down the middle of the leaflet clusters. A leaflet is a smaller leaf blade that extends from the vein. Leaflets are not independent leaves like simple leaf blades, and because compound leaves contain multiple leaflets they're able to be further classified based on the arrangement of their leaflets.
For example, palmate compound leaves have leaflets that radiate outward from the center of the leaf structure, just like your fingers move outward from the palm of your hand.
Pinnate compound leaves have leaflets arranged symmetrically down the center of the leave structure, where each leaflet appears to be stuck, or pinned, to the central vein.
Compound leaves can have other possible leaflet arrangements, but palmate and pinnate are two of the most common. Examples of compound leaves include poison ivy, locusts, buckeyes, and hickory trees.
Gingko Leaves
This diagram also includes a gingko leaf (e). But is it a compound or simple leaf? At first glance, it appears to be a single leaf, which would lead us to believe it's a simple leaf. But upon closer investigation, we see that it does not have a single, central vein. Instead, it has multiple, partly connected leaflets radiating outward from a central point. This makes a gingko leaf a palmate compound leaf.
Most of the time, it's be easy to tell whether a leaf is simple or compound, but there are a few rare instances - like the gingko - that can be a bit trickier. Tree field guides can be extremely helpful when identifying more challenging leaf structures.
Lesson Summary
Leaves can be classified as compound or simple based on their structure. Simple leaves have undivided blades and contain a single leaf on each vein. Compound leaves have divided blades that contain multiple leaflets attached to a central vein. Compound leaves can be further classified based on the arrangement of their leaflets. Palmate compound leaves have leaflets that radiate out from a central location. Pinnate compound leaves have leaflets that are arranged symmetrically down the center of the vein. While most leaves can easily be identified as simple or compound, the gingko leaf requires further examination in order to properly identify it as a palmate compound leaf.
