When a leaf isn’t (Part 1)

When you walk around the Euroa Arboretum you will see wattles with a whole range of leaf shapes. In reality very few wattles have leaves. Most have what are technically called ‘phyllodes’ (pronounced ‘fi-lodes’ where ‘fi’ rhymes with ‘pie’).

diagram (1)The photo left shows the structure of a typical plant. It has a stem, and a stalk that attaches the leaf to the stem. This stalk is called a petiole. Wattles like the Black Wattle (Acacia mearnsii) and Silver Wattle (Acacai dealbata) show this structure. In many wattles, however, the stalk or petiole becomes modified and the leaves fall off. The resulting structure is called a phyllode—a modified stalk. The phyllode is an adaption to reduce transpiration losses (water losses) in a dry climate.

Golden Wattle (Acacia pycnantha)

For the Golden Wattle (Acacia pycnantha) the phyllode looks like a broad, flat leaf. In the Spreading Wattle (Acacia genistifolia) the phyllode is spine-shaped. And you can get a whole range of shapes in between.


Interestingly, most acacias start off with leaves, but as they mature the phyllode develops. If you look in The Arb’s nursery you’ll see plenty of examples of young seedlings with the leaves growing out of the already modified stalk. These leaves eventually drop off.

Confused? Don’t be. If it’s all too scientific, call them leaves. Everyone will know what you are talking about. But check out The Arb, especially the nursery. It’s got loads of phyllodes.

Acacia seedling with modified stalk and leaves
Acacia seedling with modified stalk and leaves