Compost them for at least moths. Use.

I have several Balck Waalnut trees and the leaves from those trees are composted as well as being used for mulches and I see no real problem from doing that. A couple of years, when the leaves fell in one night into a thick pile under the trees, I cleaned them up and spread the shredded leaves over an area where there was primarily Quack Grass with some Perennial Rye growing and in about a week I did notice that the Quack Grass was being suppressed but the Perennial Rye was growing in faster and thicker.

Every article, without exception, advises that black walnut debris be picked up regularly and often so that the juglone does not affect the soil of nearby plants.
Since its not the tree itself, but the droppings of leaves and twigs that causes such chemical harm it just makes good sense to not invite trouble by putting the debris to other uses, such as putting it into composts.

If such harm could affect even slightly our plants then why do it. To say the chemcial reaction doesn't do harm is going against every mention by those that study the issue. Just because we cant see what damage might be the result is no excuse to advise others to ignore the possible harm and to suggest, because a person has "many" trees, and hasn't witnessed damage is not a reason to say that harm isn't being done.

I must say too that if a person has many...I assume then, more than 2...and considering walnut trees take on a canopy of 30 - 40 - 50 feet across, one saying 'many' then must be living on acreage of much wasted land.
White it is true that some plants can be grown near walnut trees without harm, the number is in the vast minority.
Even some trees are, respectively, advised to be not planted within certain distances from the walnut.

Oh groan; sorry for the typos in my earlier post - meant to say compost them for 6 months, then use.

JUGLANS- family is Butternut,Black walnut,English walnut.
The black walnut shell, leaves,twigs, roots, bark, wood chips all change the soil. However if you have no problem with the compost, go for it.
Do A search & you will find 2 list, one of plants that will grow near or under BW trees & one of plants that will not grow near or under Bw trees.

Here is the link. It doesn't sound as bad as I thought. I don't use anything from the black walnut in my garden. I wouldn't put it in my compost, but I am sure the University knows more than I.

Here is a link that might be useful: curt's link

Five years ago I put the leaves from a walnut (English) tree in one end of my garden(the first fall at a new to us residence). A week later, after tilling those leaves and others in, I was driving down the freeway and I remembered reading in a horse book, 30 years ago, the warning not to use walnut shavings for horse bedding due to some toxicity. I called the county extension service- the gal told me not to worry about it- a couple of days later she called me again, after talking to a horticulurist from Washington State University- there was a problem from the Jugolone in the leaves. My cucumbers wouldn't germinate even after replanting a couple of weeks later.
Beans, carrots and beets aren't sensitive to jugolone whereas cucumbers, peppers and tomatos are. I planted a few cucumber seeds in that end of the garden this year and am happy to say that they did germinate.
I've read in the last few years that you can use walnut leaves after they have been composted. I still bag my Walnut leaves separately for a trip to the waste management system but if there are some walnut leaves that have blown into other areas I just go ahead and mix them in with the other leaves for the compost bin.
Perhaps I should put the one half dozen bags and a Free Leaves sign with them out by the street, to make it easy for any compost whackos out trolling to ...score.

Why take the chance?

Even after composting walnut leaves retain the ability to suppress germination and/or growth of some veggies. The effect is not just from leaves, but also from roots, limbs, stems, or any residue from a walnut. Black walnuts are far worse than English/Persian walnuts because of higher concentrations of juglone. The roots are the worst problem followed by the leaves which are obviously more mobile. Once juglone is in soil, it takes 2 or more years of rainfall plus a lot of active fungal organisms to break it down or leach it out. Small amounts of juglone are not a problem in compost, but if the volume of leaves is more than 10% of the pile, you will get residual activity from the juglone. As in the Ohio article, long term composting tends to break it down. I still would not plant tomato seed in such compost.

Walnut leaves should never be used as bedding for horses.

DarJones

This is the one I saw 12/26/10.