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Toxicity of Eucalyptus trees

I have a young Eucalyptus pulverulenta tree. I’m concerned that it might be emitting toxic chemicals into the surrounding soil that will harm other plants. Is this indeed a cause for concern?

My instinct is that your Eucalpytus tree will probably not be toxic to most other plants. Eucalyptus is often seen growing in the midst of garden beds here in Seattle, to no ill effect. I have a tree growing in a perennial bed, and have noticed no problems. However, the leaves do contain essential oils (phenolics and terpenoids). This does make the tree more flammable, if that is a concern. Eucalyptus leaf litter (to a greater degree than exudates from the tree’s roots) can inhibit specific food crops, like wheat. This is what is meant in this University of Florida Extension article (now archived), which refers to “selective activity of tree allelochemicals on crops and other plants.”

To show how selective this chemical property can be, see the following documentation of a University of California, Davis experiment using composted Eucalyptus as mulch.

“Mulch products made from Eucalyptus are an asset to maintenance of fine landscapes. Composted Eucalyptus makes an excellent seed cover and will aid in germination and establishment of seedlings such as California Poppy. Fresh Eucalyptus is an excellent mulch for woody landscape plant materials and palms; the main effects of its use are weed control and water conservation.”

Unless you are growing your tree in the middle of a field of wheat or among other grassy plants, your landscape is probably in no danger of inhibited growth from the Eucalyptus.

You may find the following veterinary perspective (from Cornell University) on the toxicity of Eucalyptus of peripheral interest.