Allelopathic American Elm

chickencoupeApril 24, 2012

Just found out. My garden is riddled with American Elm roots and also Pecan but not Walnut. I do have a section I can move the garden to but I was sorely hoping to utilize the entire place over time and also to utilize some of the dappled shade during the heat wave.

At present my plans are to beef up the entire garden bed by composting directly on top and leaving 4-5 inches of compost to be utilized as the planting bed.

Perhaps I should make it even more dense placing cardboard - a slower type of composting material - at the very bottom of my bed as far as I can dig?

I do remove roots when I come across them but some of these are very large and immobile, of course. The canopy of this elm tree has about a 30' radius. The garden bed is positioned on only one side of the tree, of course.

(Dawn, this might be why my tomato plants seems "wimpy" when I planted them. They still are. Otherwise, they were OK. They are, indeed, stunted in growth which could be a number of things for which I am clueless.)


Thank you for reporting this comment. Undo

I just realized something. I've been using my compost soil as an amendment in the garden - like those I put the tomato plants in. As directed, I placed that compost pile in shade under a young elm tree. Its roots are growing right up into the darned pile forcing me to rip them out as I turn or sift the aged compost. It's a very large pile so the plants' reaction makes sense.

Well, crud. Now I've got to have Bill cut that tree down because that one will infest the other section of the yard that isn't infested with tree roots. Gah! We just cut down an old unkempt crab apple tree and what a mess. Seems I need to spend more time planning and pruning and moving and and. Who knew so much planning was involved. Sheesh Thank goodness I have a lot of room.


Here's the compost and the offending elm. The area to the right is free and clear. lol

    Bookmark   April 24, 2012 at 4:11AM
Thank you for reporting this comment. Undo


I'll be interested in what others say. But it seems to me that the elm shouldn't cause all that much trouble. If your tomatoes are close enough for there to be a problem, I'd suspect the problem is as much shade as it is juglone, the substance produced by walnut tree roots. Here's a link which might help. Notice that elms produce juglone in a much lower amount than either walnuts or pecans. Also, it appears that not all garden crops are affected by it. So, perhaps you might try relocating some of your tomatoes to that other area as an experiment.

Tahlequah, OK

Here is a link that might be useful: Walnut wilt

    Bookmark   April 24, 2012 at 5:05AM
Thank you for reporting this comment. Undo
Okiedawn OK Zone 7

Bon, I just cannot imagine the elm roots are alleopathic enough to cause your plants harm. I use elm leaves in my compost all the time, and have elm, pecan, hackberry and oak trees growing just outside my garden's north fence. They are so close that I can just about touch the tree limbs if I am standing inside the garden's north fence...except the fence is taller than me so I can't reach them because of the fence. I have all manner of tree roots underground and they continually move into the garden. Where they are in the top few inches of soil, I rototill and dig out what I can in the winter, but they're back again by the next winter. We have 14.4 acres but almost all of it is heavily forested, so there is nowhere I can plant far enough from trees that tree roots won't come into my garden.

Might the elm tree roots outcompete your plants for water and nutrients? Sure. But will they have a serious and adverse effect on their growth? I don't really think so. If elms and hackberries were highly alleopathic, nothing would grow underneath them in the woods....and every inch of ground beneath them in the woods has smaller trees like black cherry or redbud, and all kinds of groundcover plants. By contrast, wherever we have black walnuts in the woods, there is not much of anything growing under their canopy as far out as their drip line. From observing them in the woodland together, you can see how black walnut's alleopathy is so much stronger.

For the compost pile, just put down a couple of layers of very heavy black plastic---4 mm or 6 mm would be ideal, and put your compost on top of it. That largely will keep root intrusion from being a problem. You can get a thick row of black plastic someplace like Lowe's or Home Depot. Cardboard will decompose in a few months, so it wouldn't keep out the intrusive tree roots that keep invading your compost pile.

It takes a very long time to build healthy soil in which tomato plants will thrive. This is my 14th year with this garden and my soil isn't even close to where I want it to be. Clearly, it is a lot better that it was 14 years ago, but I didn't even see much improvement in plant performance until I'd already been improving the soil heavily every year for 4 or 5 years. You just have to work at it on a continual basis. Because heat eats compost, no matter how much compost you add one year, it will be almost gone before the next growing season. I add all the compost I can in the off season when there's no plants in the bed, then I mulch, mulch, mulch heavily. As the mulch breaks down, it further enriches the soil. I add more mulch to some bed in my garden every week. It is a process that never ends. Good soil isn't something you just whip up out of thin air by adding some organic matter to your natural dirt. It takes years of constant improvement for it to develop and evolve.

It is easy for us to blame the weather, the lack of rain, the heat, etc., when plants don't perform the way we want, but I think much of the time, the truth is that our soil just is not yet where it needs to be. The amount of improvement needed will vary depending on what kind of soil you start with, but the need for constant improvement, especially in terms of adding organic matter, never ceases.


    Bookmark   April 24, 2012 at 10:50AM
Thank you for reporting this comment. Undo
helenh(z6 SW MO)

You are way ahead of me in the garden because I'm north of you, but it takes a while for plants to look good after you plant them. It has been very windy here. Maybe your plants have not had time to take off. Elm roots are so thick and close to the ground that I don't fight them on that side of the yard. You can remove roots but more will grow. Pots that I put near the elm get elm roots in the drainage hole if I don't watch it. I never thought it was allelopathic like the walnut, but extreme competition. It is hard to keep plants watered near a tree with lots of surface roots. The big white oak at the edge of my yard does not have so many roots and under it is a great place for shade plants.

    Bookmark   April 24, 2012 at 4:25PM
Thank you for reporting this comment. Undo

My garden is pretty close to a huge elm tree. I didn't have much of a choice, but I'm not too worried about it. I've always thought of it as an issue of extreme competition instead of allelopathy as well. It gives my garden some afternoon shade and that's worth more to me than worrying about the roots. I figure it's a lot easier to rip some roots out at the end of the year than it is to hide my plants from the sun. The seeds raining down on my garden are so annoying, though. They are everywhere!


    Bookmark   April 24, 2012 at 5:46PM
Thank you for reporting this comment. Undo

I have both Elm and Hackberry (kissin' cousins) and the most serious issue I have with them is competition for water and nutrients. I don't like them because I don't know of a healthy Elm planted anywhere unless it is a newer resistant variety to Dutch Elm Disease. Hackberries and Elms both drop seeds everywhere, which I'm convinced have a 100% germination rate and if I'm not diligent, I have more Elm trees competing for water and nutrients. The only thing I like about them? They are larval hosts for the Emperor butterflies and the Question Mark butterfly and the Four-Horned Sphinx (which is rare here; I've only seen one). That is the extent of their value, other than shade.


    Bookmark   April 24, 2012 at 6:11PM
Thank you for reporting this comment. Undo

How fascinating! Both the pecan trees and the walnut trees show evidence of borers all over the trunks. In ADDITION: The pecan leaf scorch mite AND PECAN PHYLLOXERA. The mites, borers and phylloxera have infested our 1/8th acre, the neighbors', our other property of trees and even the thicket nearby. I was SERIOUSLY worried about my pecan trees last year. They were already partially crippled from these infestations. Then, the heat wave breaking a 30 year record.

The pecan tree cooling our house seemingly buttresses the roof with a base of 4 feet wide planted six foot away from the back door. We can barely afford gas for the chain saw much less to rent a bucket truck, hire someone to cut it down or repair our blessed home should it fall atop. We got very very lucky following that dreaded ice storm a few years back. It bounced off the roof leaving a crack providing minimal water damage and we were able to fix the roof and finish work ourselves. Even then, we scraped up several hundred dollars and hired a tree climber who looked like a walking beef jerky stick. It appeared he only had half his brain firing from drug use while he utilized his employer's bucket truck to give it a trim. After that we could breath a little easier.

That monster and the others seem to have survived last year when Scott was telling me pecans love heat. The complications did not push them over the edge like the walnut trees and four other trees on their last leg. There are only a couple small limbs on each of the two walnuts that are alive. When Bill finishes trimming there won't be much more than tall stumps left. The black walnuts were sweet and tasty while gracefully shading the sweet little sandbox in a unique form that cannot be duplicated. They were fashioned as if their mission was to stretch and over just the sand box. Trees are artful sometimes.

The heat wave last year prematurely defoliated the leaves and they scorched/decomposed before fall ever came around. A fall or spring without leaves on the ground is not something I've ever experienced. I think a bulk of the infestation burned but I still see mite and phylloxera. I don't know about the borers but I think they're toast. I don't really know that much other than spending a great deal of time researching these strange appearances on my trees.

The elm trees? Not a problem. Weird, huh?


    Bookmark   April 25, 2012 at 1:31AM
Thank you for reporting this comment. Undo


Maybe I hired the same fellow, with his bosses bucket truck, back some years ago. But there were two of them. And then again, maybe there's just something which draws people on drugs to work up high, wielding chainsaws!

I believe we have a number of healthy American Elm trees near us and on our property. One huge old tree shades our barn. It is gorgeous. Originating out East, I was in my 30s before I saw an American Elm.


    Bookmark   April 25, 2012 at 10:35AM
Thank you for reporting this comment. Undo
helenh(z6 SW MO)

My last tree people were professionals but the guy before just got his truck on sale. He brought a young man from his church who had a brain injury from a car accident. His driver was his father in law. The nice young man with the head injury was given the job of pushing the button or lever for the stabilizing things on the side of the truck. He was to do this when given the sign from the guy in the cherry picker. One time he did it just for fun and the guy in the cherry picker bounced up and down like some kind of carnival ride. Then the guy in the cherry picker rode in it as his father in law backed up in a narrow part of my yard that no other tree people will enter. They were using voice signals and the father in law did not hear almost crushing the main man in the cherry picker against my mulberry tree that was overhanging. Then he was dropping short cut off logs from my elm tree on the bedroom roof. That ceiling used to be popcorn that got wet before the roof was fixed. I have textured that myself and in some place the plaster is thick. I thought the ceiling would come down the whole time. Finally he admitted that he could not reach the one big branch overhanging the roof and I thankfully agreed that he should not attempt anything that wasn't safe. That is why I will now pay big bucks to get a professional.

    Bookmark   April 25, 2012 at 11:03AM
Thank you for reporting this comment. Undo

lol George. It would not surprise me! I think they like the "thrill" or they really never lose their need for excitement but it's nerve-wracking. Our elm really is glorious in its age bringing much character and charm to our little haven.


How precarious!! I'm glad everything turned out OK with that Keystone Cop operation! They make our tree trimmer look professional. LOL

My husband has the mind "if it can be fixed there's no need to buy new" but I urged him to go and buy the right chainsaw for the jobs he needed to do. After that experience I know he's more worthy for the job except when a bucket truck is needed. Instead of hiring another trimmer to finish the job we bought the saw. Bill has only known hand-me-down 3rd and 4th generation equipment. "IT SLICES LIKE BUTTER!" he exclaimed for a week. I said not a word when he lovingly placed his new chainsaw in the dining room behind the table for safe keeping. ♥ It has since made its way into the shed but has served him VERY well keeping those limbs trimmed. We managed to purchase tools for sharpening.

Some things are well worth the money!

A 500 dollar 100 feet automated power snake will pay for itself with just one use.

A cheap new self propelled push mower can alleviate stress when the grass grows faster than repairs on the old riding lawn-mower.

Get er done, but do it safe! =D


    Bookmark   April 29, 2012 at 9:59PM
Sign Up to comment
More Discussions
Seedy Saturday Seed Swap
Seedy Saturday Seed Swap. February 28, 2015 When I...
Does anyone have milkweed seeds they could share? I'd...
New subjects and thread drift
I see some threads get off topic quite often. I have...
Attracting Beneficial Insects to Your Landscape
Sometimes I think many gardeners tend to overreact...
Okiedawn OK Zone 7
Classic Armadillo Thread From 2005-2013
I mentioned the thread linked below in a different...
Okiedawn OK Zone 7
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™