Plant theory: simple leaves and compound leaves

This short article about the difference between simple and compound leaves was prepared by local botanist and ecologist Dr Kevin Mills and was published in the April 2021 edition of his monthly Budawangia newsletter. You can subscribe to Budawangia by contacting Kevin at kevinmillskma AT gmail.com. 

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When we talk about a leaf, we should appreciate that not all leaves are created equal. Leaves can be divided into two groups, leaves that are termed simple and those that are termed compound. This feature is often used as an early couplet in taxonomic keys. As the names suggest, simple leaves are not divided into smaller segments (leaflets), while compound leaves are composed of several distinct segments (leaflets). The problem for some arises in being able to differentiate between a simple leaf and a compound leaf, the compound leaf appearing to be several simple leaves rather than leaflets.

The large compound leaves of Diploglottis australis. Image by Kevin Mills.
The simple leaves of Pennantia cunninghamii. Image by Kevin Mills. 

How to tell if you are looking at compound leaves? Compound leaves do not have buds on the central stem (rachis), so if you see buds on the stem, the leaves are simple. After looking at a few examples, it becomes relatively easy to tell the difference – good luck!

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An additional note. Over on the Growing Illawarra Natives group on Facebook, we will look at a few different leaves and work out together where they are simple or compound: https://www.facebook.com/groups/GrowingIllawarraNatives.   

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