You have chinese privet on the upper left and lower right of first photo. That does not have that property, although it is a highly aggressive plant and will out-compete others.

Upper middle of first picture is Elderberry, not a problem.

Other plants in that picture appear to be a Prunus (dark green shiny leaves on bottom of picture) and perhaps a Hackberry (middle left).

Second picture has Euonymus at the bottom - does not appear to be the native one.

Last picture is Sassafras.

Knowing the names will help you figure out if these plants are allelopathic.

Not 100% sure on all of these.

First photo, clockwise from top left: Ligustrum sinense, Sumbucus, Ligustrum japonicum, (don't know), (don't know)

Second photo: only thing different is Euonymus and Sassafras.

Last one is sassafras.

Sassafras is well known to have allelopathic chemicals. Chinese privet is suspected, but hasn't been studied to any great degree. You are right about the Sycamore, by the way.

Many common trees and shrubs are allelopathic, exuding the chemicals through the roots, or via leaf litter, fruit/nut debris, leaf and stem run-off (rain).

So you would not compost with the leaves? Does the compost break down the poisonous chemicals?

My yard has elder trees, sycamore, black walnut even mostly male, and maple, all of which can be hazardous in some small way or another to gardening. Together they could cause the damage I have in my garden.

My opinion is that if I leave the grasses growing in between the rows, the plants do better because they are absorbing the poisons?

Well, it helps to know what all I have. I was going to plant elderberry, and I did not know these were the same bush. Those are edible, but not growing in the dirt very well. It's October and the berries are still green, that is the problem.

This helps, but I'm going to do a slow clean sweep of everything growing, I'm hoping to take down every bush and tree. I never knew how good oak trees were and why they were so much luck. My grandmother's property is laden with them and she always had great gardens.

Thank you so much! I appreciate everything!

Yes, composting does breakdown allelopathic properties. And to a large degree, most plants with some allelopathic properties (and there are many) are not known to be very intense with regard to those properties - the biggie is of course walnuts and their relatives with juglone. And allelopathic chemicals in most cases will be concentrated in the roots or wood, far less in the leaves or litter.

I think it a bit severe to make a "clean sweep" removing all these plants. There are various reasons why your garden may not be performing up to snuff that has nothing to do with allelopathy - general soil conditions including drainage, sun/shade, selection of plant types, climate/weather, density of any tree roots in the immediate area, etc. Have you tried raised beds? Raised beds often offer much better growing conditions than inground planting for a wide variety of reasons. Before I opted for a scorched earth policy, I'd pursue other options.....

Not scorched earth, just cut with tree root killer. I'm saving the hackberry and elderberry bushes, there is also a pair tree. I have red twig dogwood tree seed and lots of arborvitae seeds, so a hedge in place of the line of trees by the road would be welcomed. The dogwood trees won't get bigger than 15 feet, but can see most gone in a few year totaled because the roots are going to be popping new shoots. If I do a clean sweep of everything especially the Chinese privots that grow like grass in the shadier places, it won't hurt.

It's too dry to mess with fire accept in winter and we live in town on a 1/4 th acre lot. Old house built over a hundred years ago, needing repair just like the back yard does.

The sycamore, sassafrass, and walnut tree really cause a lot of problems and need to go unless I can find a way to grow something between them and the trees. Do you think arborvitaes would absorb most of the poisons? They say to mulch in between the walnut trees by so many feet and it has less of a poison factor.

I'll have to look into it, but I'm looking for a woodcutter right now. The trees have nice properties, but all together they are dangerous in case we really need to rely on the food.

I don't mean to bring up politics, but we almost went into a depression and are now talking about world wars with Russia China, so goods will be limited if anything like that should happen. Besides look at the cost of tomatoes? That is crazy and it's mostly gouging. A family or even a single person would be smart to keep a garden. Europe is better about it than the US, but I live in a rural area, even in Detroit most of my neighbors had a little garden. I only had one garden in Detroit, and it did bad due to new ground and it being planted over an old junk yard, could have been fixed, but not this yard.

Many of the others who lived here had terrible gardens and mostly planted herbs from what I can see.

I also want to make a correction, the plant I called an elderberry with the berries was the chinese privot. I've got a few hackberry and elderberry trees.

Thanks for the help! That did fix me up for the next year and I'll keep composting and maybe try just raised beds, even though I know I should try container at least once to get one good garden.

Did you say BLACK WALNUT? That's the worst/most famous allelopathic plant around.

Rain2Fall

Now add various evergreens to the pot, only a few small ones so far, but they have allelopathic qualities too. My uncle aerates his garden until you can pull anything out with a tug, and thought it would kill the plant due to heat and drought, but that seems to be the only answer to have a garden in bad soils, or at least by some instructions to get rid of juglone.

Aerate, mulch with course mulch, and a few other things including raised beds are the methods used to control them. I know people who plant next to one every year and say they never had a problem with theirs until this year, so the dry soils are creating a suction maybe taking in more than usual deeper in the soil. I'm on a hilltop, so the tree down the hill shouldn't be as much of a problem, but the suckers are what is. Little male walnut trees! The roots have the most juglone even compared to the black walnut hulls.

It's not the only thing in the yard stunting the plants. They grow nice and green, but take forever to produce fruit.