can we live with alianthus - tree of earth, heaven and hell

Hi Everybody!
I'm working on an urban gardening project in Budapest, Hungary. We're converting a gravel lot to community garden with containers for now, but we're planning to do some major work in the fall after we've had a season feeling out the conditions. We've got a wall and a row of alianthus trees protecting us from a street, pollution and wind, as well as helping reduce noise. It's a tightly packed row of trees, about 15 years old, maybe younger because they grow fast, 4-6 inches in diameter in front of the wall.  I've discovered they eat sulfur dioxide from the air and take up mercury from the soil. Nice services for the city. We'd like to keep them for all those services, if we can. Replacing them would be costly. So my question is, how?
The downsides are that they smell like rancid peanut butter if damaged. They also produce an allelopath in the soil, and their roots are reputed to break walls and into sewer mains. They invaded the bombed cities of europe after the WWII.
We're considering a few options before cutting:

1) feeding them - maybe building an embedded raised bed along the wall, while cutting back the roots that reach out into the garden space, and filling above ground level with their somewhat annoying leaf litter over time, along with some compost. The idea being to give them food and they won't need to invade our veg beds. Hmm...?

2) coppice or pollard them - maybe every other tree could be coppiced to head height. Could this decrease the competition between them, for root space and sun? They tend to send out numerous suckers if cut down- this we want to avoid. We could coppice them all to wall height.

3) a transition trench - maybe we could cut a trench, fill it with the gravel we have, for a path along the row, and try to keep their roots cut back each year. It doesn't seem to stop them, but in combination with 1)feeding, they might be deterred.

4) a companion hedgerow - with a living hedge between them and our garden, we would have them up in the low canopy story and some kind of hedge story might insulate our soil from the allelopathy and make the space wonderfully insulated from the city. But what lives near these trees?

I've hardly any experience with these trees, or trees in general, so it's all theory to me at this point.
Anybody have any recommendations? or alternatives? Who anybody in their right mind try such an endeavor?

Thanks for any feedback,
Mark

In my limited experience they do very nicely under coppice since they grow back so quickly and can produce a 6 to 8' shoot in one season. They can be very handy for using as garden stakes and such but they don't last very long 2 seasons at the most.

I just cut down a huge one in my yard because it was threatening to drop branches on our house and I was getting tired of mowing all the suckers it was sending out.  (Which I nonetheless expect to be doing for a few years as its root system keeps trying.)  So that's the first observation: you are going to be dealing with those pioneer sucker trees (shooting up to six or eight feet tall in a season) whether you cut down the trees or you don't.  The only way to manage them is to mow them like grass when they first pop up, or cut them with clippers if they get too tall for your mower.  It's simply an unavoidable maintenance task if you don't want your alianthus tree to turn into an alianthus forest.  But it's no big deal in any actively managed space.  You were going to be working in that garden anyway, right?

The good news is that I find reports of its allelopathy to be vastly over-rated.  (I find most reports of allelopathy vastly over-rated.)  Mine had lawn grass, prairie flowers/weeds, and clovers growing right up to its trunk with no observable loss of vigor.  I did have one sand plum tree transplant die in an orchard area where its suckers started popping up, but the area was full of gophers and my dogs were digging in there like mad, so I suspect physical root damage is the more likely explanation, especially since the rest of the plums in that thicket were fine.

In your shoes, I would manage like any other trees at the garden interface.  Use them for what they offer (windbreak, privacy) and manage their size to prevent competition for light, water, nutrients.  If roots and shoots start invading, prune ruthlessly. If trees die from being managed (not gonna happen), replace them when that happens.  

We have one next door and mowing does control shoots that come up from roots or seeds, but it does cause issues as my wife is allergic to it and gets very bad dermatitis the same as poison oak or poison ivy. The tree next door is over 27 years old, so should fall over on our garage soon, yay. We’ve been digging out the runners every year since we moved in.

If the trees the op has are near any neighbors l wouldn’t hesitate to extirpate them and replace with something more suitable.

We have had pretty good success at our community garden by very gently girdling the base of the tree. (cutting the cambium layer of the bark) By doing it too fast, it sends the emergency message to the tree, to pop up new shoots. After doing this incrementally, it took just over two weeks before it was safe to cut the tree. Depending on you size and amount of water, your situation may vary. Or as mentioned above, you could use it for fast regenerating bio-mass. Good luck.

J. Burkheimer! - I saw somebody on the net cutting slices around the tree to weaken it but not alarm it. However, they were then spraying some poison in the cuts. Do you fully girdle it? How wide of a strip has worked for you? I'm worried they all might be clones from one or two original trees.
By the way, they're allelopathy doesn't seem to affect mulberries (small ones). I found a small mulberry sprout growing almost on top of the trunk of a TOH, so I planted another nearby to test the 'allelopathicness'. If we get an edible bush that keeps their roots in check, it'll be nice.

These are all great observations and considerations. This thread is turning out to be very helpful.

Mark Richards wrote:Hi Everybody!
I'm working on an urban gardening project in Budapest, Hungary. We're converting a gravel lot to community garden with containers for now, but we're planning to do some major work in the fall after we've had a season feeling out the conditions. We've got a wall and a row of alianthus trees protecting us from a street, pollution and wind, as well as helping reduce noise. It's a tightly packed row of trees, about 15 years old, maybe younger because they grow fast, 4-6 inches in diameter in front of the wall.  I've discovered they eat sulfur dioxide from the air and take up mercury from the soil. Nice services for the city. We'd like to keep them for all those services, if we can. Replacing them would be costly. So my question is, how?
The downsides are that they smell like rancid peanut butter if damaged. They also produce an allelopath in the soil, and their roots are reputed to break walls and into sewer mains. They invaded the bombed cities of europe after the WWII.
We're considering a few options before cutting:

1) feeding them - maybe building an embedded raised bed along the wall, while cutting back the roots that reach out into the garden space, and filling above ground level with their somewhat annoying leaf litter over time, along with some compost. The idea being to give them food and they won't need to invade our veg beds. Hmm...?

To contain these trees you will need to be able to put in a thick barrier 1/2" (1.5cm)thick will hold the roots, then you have to dig up all the roots beyond that point since they will sucker as many have already mentioned. If you feed them, they will have the vigor to break through any barrier except for stainless steel eventually.

2) coppice or pollard them - maybe every other tree could be coppiced to head height. Could this decrease the competition between them, for root space and sun? They tend to send out numerous suckers if cut down- this we want to avoid. We could coppice them all to wall height.

Coppice is a great way to control a trees growth, But, it also means more root production because every branch is connected to a new root, so while you can control top growth, you are expanding root growth both in numbers and strength.

3) a transition trench - maybe we could cut a trench, fill it with the gravel we have, for a path along the row, and try to keep their roots cut back each year. It doesn't seem to stop them, but in combination with 1)feeding, they might be deterred.

Gravel is not a barrier, see my answer to your first question.

4) a companion hedgerow - with a living hedge between them and our garden, we would have them up in the low canopy story and some kind of hedge story might insulate our soil from the allelopathy and make the space wonderfully insulated from the city. But what lives near these trees?

The allelopathy of this tree is aimed at shrubs, bushes and other trees, not surface root type plants like grasses or even Lucerne(alfalfa), This means that any hedge row attempt will result in either non growth of the hedge plants or stunted growth of the hedge plants. (you can plant garlic under this species)

I've hardly any experience with these trees, or trees in general, so it's all theory to me at this point.
Anybody have any recommendations? or alternatives? Who anybody in their right mind try such an endeavor?

Thanks for any feedback,
Mark

In many parts of the world this species is considered an invasive and some countries have even outlawed the importation of seeds or live plants. There are many, easier to control/train species available and even fruiting trees so you get edibles as well as screening/ air filtration.
In areas that have heavy metal contamination, any plant that sequesters the contaminate will be contaminated so that usually means no food stuffs should be consumed.
If you girdle this species you have to do it in stages and the girdling needs to only be about 4 inches wide.
I've had success doing this in a checkerboard pattern and then taking the connecting squares a few a week, total time from start to finish of the girdling was 4 weeks, tree died, no extra shoots came up.

Redhawk

I also found a guy online who seeded a TOH with mushrooms, to slow stress it, I guess so it doesn't give off shoots.
Since we don't have the means to rip out the dead trees, I'm thinking it might be possible to girdle some, then when they look dead, try the mushrooms, maybe eventually improving the rockhard soil where it is.
It's growing through a layer of parking lot gravel. Anybody try mushrooms with these?

I helped a friend inoculate ailanthus with grey oyster spawn, we just drilled holes in the trunk and drove in doweled inoculant. (don't wait for it to look dead, there is no need)
It worked pretty well, only four suckers came up from the roots, those were allowed to grow a bit then they too were inoculated by cutting the new bark and hand stuffing some spawn into the cuts which were then covered with saran wrap and duct taped in place.
We did this three years ago and his land is free of ailanthus today.

Please be careful with your Tree of Heaven as it seems to be a host plant for the spotted lantern fly. Spotted lanternflies feed on the sap of a plant and when there are high populations of them, they can cause significant damage. They feed on over 70+ plants, including important forestry and agricultural crops. Spotted lanternfly was first discovered in the United States in Berks County, PA in 2014. It has since spread throughout 13 counties in southeastern Pennsylvania, which the Pennsylvania Department of Agriculture has designated as a spotted lanternfly quarantine zone. In 2017, spotted lanternfly was also found in Frederick County in Virginia. In 2018, three New Jersey counties (Mercer, Warren, and Hunterdon) were quarantined for spotted lanternfly.Both the U.S. and Pennsylvania Departments of Agriculture are working on control and eradication measures in the quarantine zone. Primarily, this involves removing their preferred host (an invasive plant called tree-of-heaven), and leaving “trap trees”, which are trees baited with insecticides to kill the spotted lanternflies.

Any updates on this story?

Re: tree of heaven infestation:
I know that Tree of Heaven is host for Samia sp. silkmoths used to make Eri silk.  I don't know if the larvae of Samia sp. are edible like the larvae of Bobyx mori (normal silkmoth)... but perhaps something that people with a TOH problem could consider... grow silk moths, make Eri Silk... and maybe the larvae are edible?
I've raised SMALL quantities of Samia ricini as an educational project.  They were fun and easy to rear (I did not have TOH so had to use less ideal host plants), but might be a pain to do large scale.