Australian Pine

Casuarina equisetifolia

The Flowering “Australian Pine” Tree

Ironwood trees are often called Australian Pines, but they are not a pine at all. To a casual observer it might look like they have long needles that come off the branches of the tree, and small cones that form in clusters on the branch. However, instead of being a gymnosperm, this is a flowering plant. It is more closely related to lillies or green beans than it is to a pine tree.


Ironwood trees are native to Australia and a few of the surrounding islands. They have been introduced to several places around the US and have been particularly invasive in Florida and Hawaii.

Ironwood as an invasive species

Ironwood trees were first introduced to Florida and Hawaii along beaches to stabilize the sand. In Hawaii they were also introduced to the hillsides to prevent soil erosion. The main problem is that ironwood trees can form monocultures and shade out native plants. The needles that fall have chemicals that leach out and essentially kill all other competitors. It’s a type of chemical warefare known as allelopathy.

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Written by Rob Nelson

Rob is an ecologist from the University of Hawaii. He is the co-creator and director of Untamed Science. His goal is to create videos and content that are entertaining, accurate, and educational. When he's not making science content, he races whitewater kayaks and works on Stone Age Man.

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