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another quick juglone question

Posted by nevermore44 (My Page) on
Mon, Nov 7, 11 at 10:10

I found a source for shredded leaves from a township that collects leaves from it's residents. They offer them back to the same residents, but there is a mountain of them from years past, so they are quite willing for "out of towners" to take some off their hands at no cost. The leaves are only collected from people who pile them on their lawn edges (not street gutters) so I am hoping that their isn't too much oil and car residue in them. Plus that fact that I won't have to pay for shredded bark mulch anymore is nice too. I live in a newer subdivision aptly named Weathered Oaks… Which is probably is the first thing they cut down when they made the subdivision… so the leaves from the young trees pretty much just blow away in the fall.

My question is in regards to the walnut leaves. I have found a good amount of walnuts throughout the leaves, so I then assume there are leaves too. The compost I picked up is fairly well composted and mostly leave mold. From prior posts… I am not too worried on the juglone from this batch. It will be mostly dirt by the spring at the rate it is already composted.

I am planning on going back soon to get freshly shredded leaves from this fall to use for next years mulch. In regards to the juglone in those leaves, since I only plan to use them on my perennial beds (not veggie), does juglone only inhibit seed germination or does it actually impair growth on live plants?

On an aside note, I applied about 3-4 inches of the leaves 4 weeks back… and yesterday I planted down some bulbs. Pulling aside the composted leaves, I was shocked to see how many worms there were. So it's good to see the benefits of using leaves vs shredded bark mulch has already kicked in.


Follow-Up Postings:

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RE: another quick juglone question

Composted walnut leaves are fine for all gardens/plants. Use the free compost!


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RE: another quick juglone question

I dealt with the juglone problem while sharing a garden at a neighbor's place with 2 huge English walnut trees. I did some research and forwarded the results to him, and I think they may be useful for you too.

Here are 2 articles about the toxicity from English Walnut trees. Unless your trees are grafted to a black walnut root stock, the amount of juglone is much diminished. That said, they still suggest keeping certain plants away from the roots and drip line of the trees (like tomatoes & potatoes). There's a list in one of the articles.

http://www.hort.purdue.edu/ext/HO-193.pdf
http://www.omafra.gov.on.ca/english/crops/facts/info_walnut_toxicity.htm

They also suggest that you should be able to compost those leaves for future use. I read that it takes about 30-40 days for juglone to break down. One of the best ways of dealing with what does make it into the garden, is to have more organic matter, hence more microorganisms, which are happy to consume and break down the chemical as part of their daily diet. Unfortunately, those bugs don't like massive quantities of commercial fertilizers (kills them), nor do they behave well when rototilled (population explosion then an early demise).


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RE: another quick juglone question

Since they are municipal leaves I don't think there is any way for nevermore to know what kind of walnut trees they came from. Around these parts (MO) there is a significant population of native black walnut. I don't know an English walnut to look at it, but the black walnuts (with or without husk) are easy to identify.

Anyway hopefully the articles posted above will have the answers.


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RE: another quick juglone question

Thanks for the info. They would most like be black walnut in this area. They will be mixed greatly with many other species of leaves and i don't use synthetic fertilizers.. so if it degrades over 30-40 days... i suppose i will be just fine. I guess i could always do the tomato seed germination/growing test to check every once in a while.


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RE: another quick juglone question

The only "problem" I have seen with using only the leaves from a Black Walnut tree is that the Quack Grass growth was suppressed but the Perennial Rye grass was not. When the Black Walnut leaves are mixed with other tree leaves there has not been any observed problem.


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RE: another quick juglone question

  • Posted by jolj 7b/8a-S.C.,USA (My Page) on
    Tue, Nov 8, 11 at 13:15

There are some tWo hundred plant that can be harmed from the Black walnut & juglone.
But compost from the leaves of walnuts & pecans have not hurt my plants.
I even mulched some tomatoes with pecan leaves one year & got a good crop.
I was not watching what I was doing & mulched with the wrong bag of leaves.


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RE: another quick juglone question

mustgarden, would love to be able to read what you read, "I read that it takes about 30-40 days for juglone to break down."

Do you remember where you found that info? I asked a similar question about juglone in compost with a lot of pecan shells and didn't get any info this specific.


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RE: another quick juglone question

Do a google search on "Juglone" and you will find a number of short articles by state universities. Some have lists of plants affected.


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RE: another quick juglone question

List of affected plants are everywhere, and are published in regard to growing within the drip line of a walnut tree. I would like to have some info sources about how long the juglone takes to break down, the topic of this discussion.


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RE: another quick juglone question

From Ohio State University:

"Walnut leaves can be composted because the toxin breaks down when exposed to air, water and bacteria. The toxic effect can be degraded in two to four weeks. In soil, breakdown may take up to two months. Black walnut leaves may be composted separately, and the finished compost tested for toxicity by planting tomato seedlings in it. Sawdust mulch, fresh sawdust or chips from street tree prunings from black walnut are not suggested for plants sensitive to juglone, such as blueberry or other plants that are sensitive to juglone. However, composting of bark for a minimum of six months provides a safe mulch even for plants sensitive to juglone."

Here is a link that might be useful: Whole article


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RE: another quick juglone question

Good article, thanks for sharing.


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