Re: [gardeners] Blackwalnut

Bargyla Rateaver (
Tue, 23 Oct 2001 19:35:23 +0100

thank you for that very good info, can be added to m;y; files.

bsk wrote:

> This is one of the most complete articles I have seen on Blackwalnut trees
> Black Walnut and Juglone Toxin
> The black walnut tree emits a toxin that hinders the growth of many plants
> in its near proxcimity. Though many plants are effected here are some plants
> which tend to do well growing near this tree.
> <SNIP>
> Black Walnut Toxicity to Plants, Humans and Horses
> Richard C. Funt
> Jane Martin
> 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.
> <SNIP>
> 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.
> <SNIP>
> Ranchmama
> Okie zone 7a


Bargyla Rateaver