I THINK, although I am not sure, that eucalyptus leaves and bark are allelopathic - they prevent seeds from sprouting under themselves. I don't remember if they will also kill off existing plants, but I would strongly suggest you google and see for yourself. I might consider using the leaves, even mixed with other leaves, as a mulch for established plantings, but wouldn't add them to a compost pile or use them in areas you want seedlings to sprout, without being sure it's safe. I do know that NOTHING else grew under the eucalyptus trees in Florida or in San Francisco.

Because Eucalyptus does have alelopathic properties people tend to attribute all products of the tree with that same property, however I can not find any indication this is true. Like the leaves of the Black Walnut, "Juglans nigra", also has this property but I have not seen any problem with using the leaves in compost or as a mulch. One benefit may be that apparently the leaves from Black Walnuts will suppress growth of Quack Grass.

I got curious and Googled it (allelopathy eucalyptus) - from what I can gather, from studies in Australia and in CA, the leaves, roots, sap, etc., are allelopathic. There was a comment in one of the articles that the effect was diminished after 9 months, so cold composting/piling the leaves up for a year might work to make it safe for mulching everything except seed-beds, especially since it's a mixture of leaves. Otherwise, I think I would use them, sparingly, where I didn't want anything else to grow, like under established trees and shrubs. Because the "toxin" seems to be water soluble, I would be reluctant to use it on new plantings and their struggling-to-get-established root systems. Sorry to rain on your parade - a "windfall" (sorry, I couldn't resist) of leaves is not something I would want to pass up or not use.

If worried- compost them first. That will destroy any harmful effect.

g'day kathy,

euc' leaves won't cause you any problems in a balanced system, the propewrties that everyone bandies about occurs mostly with trees in the wild, in times of drought or when they grow in impoverished areas, they then will stop other seedling trees from sprouting inside their drip zone so as to not have any competition for available resources.

they will not however stop grasses and minor plants from growing in the drip zone, and actually they and whatever grows under them thrive on the companionship, the leaves that fall and the dew that drip off the euc' leaves nurture the minor plants who then create their own mulch layer that in turn keeps the soils moist and feeds the euc' feeder roots.

we owned a property (70 acres) in med' rainfall area, and our healthiest euc's and grasses grew together.

now not sure which eucalypts your neighbour has but one can only hope they aren't the forest tree variety that grow to enormous heights, as euc's are not a safe tree to have in the 'burbs they are a forest tree.

len

Here is a link that might be useful: len's garden page