All varieties of eucalyptus are definitely allelopathic but that doesn't mean that absolutely nothing will grow under them. There are always plants that are able to overcome the organic compounds thrown of by allelopathic plants.
Those compounds seem to break down in the compost pile.

I know my oleanders that grow under my eucalyptus trees have no problem growing.

Greg
Southern Nevada

Nope. The "problem" is that their roots colonize every square millimeter of soil ,thus out-competing other plants.

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Very few things grow in the eucalyptus groves around here.

I compost a little eucalyptus but I'm never anywhere near violating the 10 percent rule.

Those damn eucalyptus acorns never break down.
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rott ... your mentioning the "acorns" makes me think of the Flowering or Blue/Red Gum varieties ... which I have not observed anything growing under. Maybe they either throw a denser under layer or have stronger exudes.

My Silver Dollar & Lemon Scented tree 'seeds' are half the size of a pea and break down quickly. [and hurt when they get inside my garden shoes ] Another benefit to these varieties is that bees love them. I think that in other countries [Australia, China, India] bee food is a primary reason for growing the trees.

BTW ... thanks for your thoughtful responses ... I'm still on the fence ... no bad effects in my experience, but seems like the whole 'expert' world is lined up on the side of 'toxic'.

Creosote was thought to be alleopathic because very little grows near them in the wild, but testing showed that it was just super-competitive for water and nothing could make it past the sprout stage.

Either its hair roots can survive dehydration and revive when there is a rain and suck up the water before other plants can react, or it can sprout them at a phenomenal speed after a rain.

Allelopathic properties have been found in Eucalyptus but I have no doubt a greedy root system has a lot to do with stunting of nearby plants. Nature often has multiple ways of achieving a desired result (from the point of view of alellopathic plants) and often uses them in combination.

I also tend to agree that they are serious competitors. The ones around here usually have upwards of 90% bare soil surrounding them. That said there is a small plantation of bluegum near to my house and I have noticed that another Australian genus the wattles (Acacias) tend to germinate and live side by side with them quite happily, although this could just be because both types of plant have evolved together back in their native homeland.

A great example of eucalyptus growing side by side with veggies and fruit trees (as they are managed intensively for the use of there organic matter and root activities, see video! amazing results by Ernst Gotsch and his agroforestry systems: www.agendagotsch.com or youtube: https://vimeo.com/146953911

I have carried out habitat restorations in Southern California. One of these was adjacent but not underneath a Eucalyptus woodland. As far out as just where a few leaves arrived by wind over the years, the plants struggled, whereas, where no leaves could be found, the plants grew robust as one can expect. This was a lesson to me, as before this I assumed nothing grew within them due to heavy litter. What can occur side-by side and underneath are Anacardiaceous members, including Peruvian pepper, poison oak, sumac, and lemonade berry. Think about that. Similar compounds?

So, as several journal articles have pointed out, allelopathy is at play. My latest drag is the soil I bought from a local supplier didn't keep Eucalyptus out, and even though I have since replaced6 inches with my own compost, everything is stressed, and there will be no salads or collards this winter.

Folks who who spread the allelopathy myth-myth are damaging to gardeners and land managers, and should stop putting their malinformed opinions out there. The putz who put my soil together probably was confused by folks that said there was nothing to it.

what I'd like to ask anyone who knows is: how long does it take for the compounds in soil to become non-toxic?

@patrickmcconnell10,

Hello Patrick, great to hear from you about the Anacardiaceous members and your experiences. About your question: i have spoken to Martin Crawford a leading figure in agroforestry (see his site https://www.agroforestry.co.uk/) about this subject. He told me that a pile of shredded eucalyptus would loose its allelopathy after about a year. This might not answer your question completely as roots of allelopatic plants in the soil are under different circumstances than shredded in a pile. But perhaps it helps knowing this timeframe for shredded material. Although i understand your critical opinion towards people telling that eucalyptus doesn´t harm, i have also followed a workshop with Ernst Gotsch (see my earlyer comment www.agendagotsch.com) where he talks about his experiences gathered over 30 years growing forests. And yes he mixes them with bananas and other species, cabbages, salads etc. and it seems to work more than fine. I guess this i due to the fact that he uses not only eucalyptus but a divers abundance of organic matters from various sources. And at this point in my experience it seems work quiet good! So i guess diversity is the key.. Adding more organic matter of many different sources can level things out. This is the video i was talking about https://vimeo.com/136423275

By the way in the workshop by Ernst Gotsch we were told to put organic matter on top of the soil as a mulch (So it has time to loose its toxics). So do not mix it "in" the soil as woodchips will also rob your soil from nitrogen this way. It needs to decompose on top and brought in the soil by bacterial life and earthworms.

I think that normally, nothing much likes to grow under Eucalyptus, although I am sure Acacia would not have a problem and that the two would help each other (or at least the Acacia would help the Euc).

I often see soil built up under a Eucalypt, and there will be plants growing happily in that. However, I think it is bad practise and unhealthy for the tree.

Many Acacias are let loose out here are from Australia, and that makes sense. Thanks Jobleijh for broadening the discussion.

I have wildflowers self-seeding under mine, but I don't compost the leaves, just in case.

I don't have any trouble growing things under the neighbour's very large lemon scented eucalyptus trees. They shed a lot of bark and leaves which I spread around the garden

there are cycad, begonias, bromeliads, clivia, hydrangeas, grevillea, blue ginger, native orchids, a Bangalow palm, firewheel trees, a chocolate tree and many other plants that don't seem to be adversely affected (in Sydney, Australia)