HankB
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is Black Walnut poisoning my compost?

I have a compost pile consisting of two wire mesh bins each about 4 feet (1.2m) on all sides. I feed it yard waste and plant scraps from the kitchen. I used to put black walnut leaves and walnuts in it too. (Now I compost the leaves separately and leave the walnuts to the squirrels.) They are now within the drip line of a black walnut. I'm wondering if juglone is soaking into the compost and causing deleterious effects to the plants in the garden where it is applied. Some plants to which I have applied compost have not exactly thrived.

Does anyone here have any insight into this?

Thanks!

john gault
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Re: is Black Walnut poisoning my compost?

I think not. I believe all the talk about the effects of juglone from black walnuts is way over-stated; I'm not saying it's a myth, just way over-stated. There are a lot of myths in gardening, such as Pine straw mulches making the soil acidic, that's a myth, but from what I've read on juglone, it seems to be a fact that is just way over-stated. Here's some good reading on that: https://gardenprofessors.com/walnut-warfare/

https://puyallup.wsu.edu/wp-content/upl ... -chips.pdf

I would look for other causes of why certain plants have not been thriving. Things like sun exposure (too little; too much), over-watering....

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rainbowgardener
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Re: is Black Walnut poisoning my compost?

That has been my impression also, that people are way more afraid of juglone than they need to be. I have grown things under a black walnut tree and the main problem is the shade. Anyway the juglone breaks down readily in the composting process, so it would not be found in any finished compost. It also breaks down in the soil, but slower.
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jeff84
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Re: is Black Walnut poisoning my compost?

I wouldn't compost nothing but green living walnut parts, but even if you did once its aged a bit it would be ok to use. so if its just a small part of the input material the compost is good to use as soon as it is done. its the fresh living material that poisons some plants. there are lots of plants that can tolerate juglone even in high doses. I have seen very healthy vegetable gardens growing directly under black walnut trees. on the south side of them so they got plenty of sun.

toxcrusadr
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Re: is Black Walnut poisoning my compost?

If I understand the original post, the concern is that locating the pile under a black walnut tree is exposing the compost to juglone? Definitely not. It does not drip off the tree or anything like that. It shows up in different amounts in roots, wood, leaves and nuts. Possibly the roots exude it into the soil, but that's the only way it really comes out of the tree except in the form of leaves and other tree parts.

And yes, it does decompose in the compost. I would not hesitate to compost walnut leaves, especially when mixed with other ingredients. Now last weekend I finally dealt with a pile of sawdust from two seasons of sawmilling and a lot of that was walnut. Sawdust doesn't decompose very fast on its own and rather than risk mulching the garden with this stuff, I used it as mulch on a walking path. If it inhibits plant growth that's a perfect spot for it. If not, nothing lost. :-]
Trail Mulching 060317.jpg
But if I had enough 'greens' (fresh manure or grass clippings) I could compost this stuff too.
Tox

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Albert_136
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Re: is Black Walnut poisoning my compost?

This is on topic but off thread, I think is the way they say it. I like to read what the '.edu' sites have to say about such questions. Here is one example. Black Walnut: The Killer Tree | News - In most cases, the damage caused by black walnuts to other plants is a combination of the presence of juglone in the soil, and the competition for light, water and nutrients. However, juglone can cause severe damage and even kill solanaceous crops (tomatoes, potatoes, peppers and eggplant).

https://www.extension.iastate.edu/news/2 ... 070701.htm

HankB
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Re: is Black Walnut poisoning my compost?

Thanks for all of the replies and views. The consensus seems to be that it will contaminate the compost from runoff but could if the roots grow up into the compost. My concern for runoff relates to the sap deposits that accumulate on any vehicle parked under a Black Walnut.

As an aside, I removed a 'stray Black Walnut' from the garden. It was about 2" in diameter. (Yes, I am a b it behind... ;) ) It was a couple feet away from an asparagus plant which did great last year and simply did not emerge this spring. As I dug up the root of the Black Walnut I was surprised to find what I believe to be asparagus roots. I wonder if the Black Walnut was inhibiting the asparagus and if that will now come up with the Black Walnut removed.

best,
hank

toxcrusadr
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Re: is Black Walnut poisoning my compost?

Time will tell on that one.

The tree sap should not contribute much to an average size compost pile, and again the stuff does decompose in the compost.

If roots are getting up into your compost, it's sitting there too long, IMHO. If you get two batches a year out or at least turn it over and disturb it, you won't get tree roots up in it.
Tox

HankB
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Re: is Black Walnut poisoning my compost?

I ran a test. I planted some tomatoes (rather late in the season, but that's another story.) I got three each of two varieties. I "sacrificed" one of each variety for an experiment. I dug in a healthy spadeful of the compost into each hole. The rest of the tomatoes got a similar treatment but with some recently acquired horse manure (partially decomposed with lots of straw stable litter.) The two plants with the compost got off to a better start than any of the others. Tomatoes are one of the species sensitive to Black Walnuts so this pretty much confirms that there is no problem with a compost pile under Black Walnuts.

Thanks!

toxcrusadr
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Re: is Black Walnut poisoning my compost?

Excellent use of science there!
Tox

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