I was doing research on walnuts and it sounds like walnuts puts something into your soil that will kill a lot of plants around it. There seems to be 201 varieties of plants that have become tolerant to it however. Many seem to be the plants we would want like bee balm, asparagus, cherries, pears, peaches and a lot of flowers. Since a lot of desirable plants are tolerant to it I wonder if it could be used as weed control. I will think a list to this. There are some that may be desirable like apples, peppers, potatoes and blueberries but far and in between. 201 Plants Compatible With Black Walnut Tree, Juglone – GrowIt BuildIT
Here is a copy of a tree guild that includes walnuts, with species minimally (or not) affected by the juglone toxicity.
It states I need access.
I approved it!
The weird thing is I have seen contrasting opinions about it. Many say no to apples and asparagus but I see your list has it and websites have disagreements on if pears can survive it or even be affected.
I think you might be looking at a separate guild. The only fruit trees listed on this one are pawpaw, persimmon and mulberry. The apples have a different guild.
I have several walnut trees and not much really looks to be having issues near them. Especially weeds. Personally I think the shade they create would kill more weeds.
You’ll still have grasses and weeds under walnuts…just fewer species/kinds of them!
I’ve not done a deep dive on the subject…and won’t, but I wonder how much of the ‘allelopathic effects’ that have been attributed to juglone are actually due to shading and competition for moisture/nutrients, with the large BW winning out over smaller trees/plants.
Ben Bishop, at the MU Agroforestry Research Center, has alluded to preliminary data from some alley-cropping trials, indicating that differences in vigor, growth habit, height to first-tier branching, etc., among different BW cultivars, has a surprising effect on productivity of wheat and soybeans intercropped between rows of purpose-planted BWs.
Do black walnut trees have alleopathic effects on other plants ?
Of the walnut species (@30 best I recall), Eastern Black Walnut (Juglans Nigra) produces the most juglone. However, only a mature tree produces enough to seriously affect plants growing nearby. I have a grove of 20 year old walnut trees planted on 20 foot triangle spacing that showed very little suppression of competing vegetation until they closed the canopy about 5 years ago. It is possible to collect leaves from under a walnut and spread them thickly in an area to take advantage of the juglone for woody plant suppression. Most of the juglone produced by a walnut accumulates in the soil beneath the tree from the roots and also from leaves. Remove the walnut tree and residual effects will make the soil toxic to many plants years later. It lasts longer in clay soils.
Native blackberries and most grasses are immune to juglone. Bluegrass is symbiotic with walnut meaning that where walnut grows, bluegrass is almost always found nearby. A story from NNGA years ago had 2 walnut growers and university professors traveling to Florida arguing along the way just how much walnut and blue grass combine. In deep south Georgia, they saw a large walnut tree in a pasture and walked to see. As you may guess, they found blue grass growing and thriving. Blue grass is not adapted to heat so the fact it was there in south Georgia infers the walnut created a microclimate that was ideal for it to grow.
I saw pawpaw trees growing and thriving beneath Gerald Gardner’s trees back in 2003. Pawpaw is a shade adapted species that often grows at the dripline of other tree species. Walnut does not seem to affect it.
As a child, I picked many a quart of black raspberries from under black walnut trees along a branch. I did not have any bluegrass at all under any of these trees…only in the yard of the house we lived in. Bluegrass is not native in many areas even in Kentucky.
Juglans nigra is.
Junipers, paw paws, privet, golden rain tree, tulips, dandelions, gladiolas, asiatic lilies, daylilies, daffodils, hellebores, plumbago, are only a few of the plants I grow in proximity to large black walnut trees.
It’s interesting, though, to see symbiotic relationships being studied, and also the effects in shade and with differing soil types.
The squirrels have given me seedlings all over my plot of land, and unless they are part of why my old pears are struggling, it has not affected much of the local growth. Most of them are in areas the former owners did not try to manage, so I couldn’t say if anything in the yard would have suffered with closer proximity or if there was an uphill from the house to deal with runoff. I’m thinking you would need to concentrate it somehow, or specifically make a compost from the debris to use as a mulch to use it with intent. So much is not affected, that I think you would just change the culture of your “weeds” moreso than eliminate them.
I noticed the same thing. I always thought they meant crabapple and maybe not every single species of apple or other words trees that are native in the environment have a better chance of survival?
The three muscadines I planted next to a drip line of a small pecan are not doing as well as the other 10 I planted in the open, could also be the lack of morning sunshine?
I have a paw paw growing under my black walnuts trees with no problems. I will warn you though that mustard garlic thrives around my black walnut trees. Invasive honeysuckle and burning bush are also not affected by the juglone as it seems.
There is a cat litter made out of crushed walnut shells. Would there be any risk in using it in the yard? I’ve stayed clear of it for fear of it conraining juglone
I mulched up my pecan leaves and nuts last year. They’ve been piled up degrading the last 12 months. I just put this pecan leaf mulch around all of my fruit trees so I’ll know if the pecan leaves and leftover nuts cause a problem. Figured it was worth trying before buying a dump truck full of mulch. If I remember right the pecans are not as bad as walnuts and each tree can have different levels of juglone and I believe I read that it comes from the majority of the root system not necessarily the leaves or nuts?