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Using dirt from under Walnut tree

Posted by mnten z7tn (My Page) on
Fri, Apr 21, 06 at 15:32

I have read that Walnut trees are toxic to certain plants and shrubs. I was going to use some nice dark soil from underneath a Walnut tree to transplant some bluberries. Should I abandon this idea?


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RE: Using dirt from under Walnut tree

The roots of Black Walnut (Juglans nigra L.) and Butternut (Juglans cinerea L.) produce a substance known as juglone (5-hydroxy-alphanapthaquinone). Persian (English or Carpathian) walnut trees are sometimes grafted onto black walnut rootstocks. Many plants such as tomato, potato, blackberry, blueberry, azalea, mountain laurel, rhododendron, red pine and apple may be injured or killed within one to two months of growth within the root zone of these trees. The toxic zone from a mature tree occurs on average in a 50 to 60 foot radius from the trunk, but can be up to 80 feet. The area affected extends outward each year as a tree enlarges. Young trees two to eight feet high can have a root diameter twice the height of the top of the tree, with susceptible plants dead within the root zone and dying at the margins. The juglone toxin occurs in the leaves, bark and wood of walnut, but these contain lower concentrations than in the roots. Juglone is poorly soluble in water and does not move very far in the soil. [From Ohio State University Extension Fact Sheet HYG-1148-93 by Richard C. Funt and Jane Martin]

The Ohio State University Extension and the American Horticultural Society have reported that R. nudiflorum, Pinxterbloom Azalea, and Exbury Azaleas Gibraltar and Balzac will grow near Black Walnut and Butternut trees. They also list many other plants that will grow in the root zone of these trees.

If you look at the chart, blueberry (Vaccinium) is not on this list. So if you have black walnuts, then don't use the soil around blueberries.

Here is a link that might be useful: Plants compatible with black walnut.


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RE: Using dirt from under Walnut tree

hackberry trees also produce the juglone...., which creates a toxin when it comes in contact with soil.

I have tried some of the recommended resistant trees and shrubs in such soil, and have encountered a 50 percent death rate of those I tried. Hopefully, since the offending hackberry trees have been removed well enough so that no suckers are popping up any more, the toxin in the soil will begin to loose strength over time.


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RE: Using dirt from under Walnut tree

  • Posted by bboy z8 WA USA (My Page) on
    Sun, Apr 23, 06 at 17:29

Chances are you'll also be taking away walnut roots, which won't help the trees any.


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RE: Using dirt from under Walnut tree

The effects with hackberry are entirely different. In fact the effect is so different that hackberry will not grow under black walnut trees.

Hackberry produces ferulic, caffeic, and p-coumaric acid rather than juglone. It is primarily affects herbaceous materials, not shrubs.

The link below is to a chart of other allopathic plants and their effects. Note that some grasses are toxic to rhododendrons and azaleas.

Here is a link that might be useful: Some allelopathic plants, the chemicals they produce, and the plants they affect.


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RE: Using dirt from under Walnut tree

Sorry about using the wrong term of what hackberry trees produce. But my experience with them is that there are shrubs which I have not been able to grow easily near hackberry trees. Specifically not within 30 feet of a scrubby looking hackberry which is planted in a neighbor's yard along the dividing fence. That lead me to believe hackberries kill much more than just herbs and grasses.

First a foster holly died in when planted about 15 feet from that tree, After that a Scarlet oak died, and after that a two Thuja 'Green Giant' trees died. About 40 feet away and more all three of those trees are growing nicely. There is no other aspect I can see which might have affected those trees which died, if it was not the neighbor's close to my property growing Hackberry tree.


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RE: Using dirt from under Walnut tree

hackberry wouldn't have killed a red oak. this is an interesting subject about trees producing substances that kill other plants. i've read sycamore also causes problems with some grasses. i haven't really seen solid evidence that walnuts will kill hackberries (sugarberries in this case)around my area. i wonder how much depends on the soil and possibly other growing conditions. one place i saw, an old abandoned farnhouse, had several black walnuts growing well a few years ago, now only one is hanging on, but there are several hackberries in near proximity thriving. the walnuts may have died from accumulated drought conditions over the past few years, not sure of their demise, but one thing seemes fairly certain- the walnuts didn't kill the hackberries


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