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permaculture - [permaculture] Fwd: Re: [grazersedge] Re: Killer oak trees/walnuts

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  • From: Mark <mpludwig@facstaff.wisc.edu>
  • To: permaculture@lists.ibiblio.org, midwestpermaculture@yahoogroups.com
  • Subject: [permaculture] Fwd: Re: [grazersedge] Re: Killer oak trees/walnuts
  • Date: Sun, 01 Dec 2002 12:11:39 -0600

Date: Sat, 30 Nov 2002 18:52:04 -0600
From: Lucky Pittman <Lucky.Pittman@murraystate.edu>
Subject: Re: [grazersedge] Re: Killer oak trees/walnuts
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> > Walnut trees are another tough cookie. Nothing grows under a
>walnut tree,
> > not even grasses because that juice from the shell surrounding the
>nut is
> > apparently toxic to competitors. And even when that walnut tree
>is cut
> > and removed, that toxin remains in the soil for years, and nothing
>grows.

Now y'all are talking about something I know a little bit about. Many of
my friends call me Dr. Nutman(I think it's because of my passion for nut
trees ;>)
Eastern Black Walnut, J.nigra, does produce juglone - as do the other
members of the walnut family - and the hickories, as well. However, none
of the others, with the possible exception of shagbark hickory produce
enough of this compound to exert much in the way of an allelopathic
effect. Juglone is produced by the roots, and is also present in the
leaves and nut husks, and even after the tree is cut, it may remain in the
vicinity of the rootzone for a few years before it all dissipates/leaches away.
There are a number of plants which have been shown to be susceptible to
juglone toxicity, but most are ornamental plants and garden
vegetables. In most instances, however, the inability of folks to 'grow
things' under a big black walnut is because that big old tree, with its
extensive root system is better able to outcompete those underplantings for
available nutrients and water. Shading also plays something of a role, but
since BW is usually one of the last trees to leaf out in spring and one of
the first to lose them in the fall, it's less a factor than with a large
maple or oak, but certainly factors into the equation.
I've never noticed any real problems with grass growing under - in fact,
right up to the trunk - of a big old open-grown BW out in a pasture.

Lucky



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Mark P. Ludwig
Poultry Research Lab
University of Wisconsin -Madison
608-262-1730 WK
608-846-7125 HM




  • [permaculture] Fwd: Re: [grazersedge] Re: Killer oak trees/walnuts, Mark, 12/01/2002

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