So walnut trees poison the soil?

[verde]

We have several walnut trees on our property and certain things seem to die around them. Someone told me that walnut trees send out some type of chemical in the soil around their root system and beyond. That would explain some of the foliage dying. Has anyone else heard about this? Do I need to cut down some of these trees?

[MissMommyNiceNice]

Yes, they can poison certain plants. Even if they are far away from you, their roots still leach the toxin into the soil. The shells also can be poisonous, and it is a bad idea to ever plant a black walnut near a stream. It can kill hte fish & bugs.

I would just plan my garden accordingly. Even if you cut them down, the roots are still underground growing & leaching. I've heard that raised beds can help. Tomatoes take it especially bad. Other plants not so much.

Too bad they don't kill the damn squirells, though!

[goldfinches]

DH has grand plans of planting an acre of these as a legacy to leave our children. I am trying to figure out how much free land I would have to leave around them because of their poison. Does anyone have any idea? Verde, how far out are your plants dying?
(if you plan to cut yours down, see if you can sell them - they're worth a lot of $$!)

[birthgreeter]

got this info from a site about walnuts...
"Allelopathy involves a plant's secretion of biochemical materials into the environment to inhibit germination or growth of surrounding vegetation."
here are a few plants that you can grow near walnut trees:
* Flowering dogwood
* Canadian hemlock
* Hickory trees
* Lilac trees
* Privet (invasive)
* Forsythia
* Sumac shrubs
* Sweetgum trees
* Shasta daisy
* Hosta
* Lamb's ear
* Scilla siberica
* Wisteria plants
* Yarrow flowers
Here is another site with some info...I copied and pasted a little of it on here , but there is a lot more info on there....
http://lancaster.unl.edu/hort/Articl.../Juglone.shtml
Since ancient times, scholars have suspected that walnuts have harmful effects on nearby plants. In the 1880s, scientists isolated a compound called juglone from the fruit of walnuts. They demonstrated that injury and sometimes death result when this phytotoxic material interacts with susceptible plants.

In addition to the fruit, juglone has also been found in the leaves, branches, and roots. The actual concentration in each part varies with the season. In spring, juglone is concentrated in the rapidly growing leaves. The amount of juglone in the roots remains relatively high throughout the summer. The concentration of juglone in the hulls of the fruit increases as the crop matures. All species of the walnut family produce juglone. Black walnuts have the highest concentrations. Relatively small amounts are found in butternut, hickory, and pecan. Most toxicity problems are caused by the black walnut.

The sources of juglone in the soil include both living and decaying plant material. Rain droplets leach juglone from the buds, leaves, and twigs. The decomposition of plant debris by soil microorganisms also releases juglone. Living roots exude juglone into the surrounding soil.

Vegetables susceptible to juglone include tomatoes, potatoes, peppers, and eggplants. Symptoms include reduced growth, wilting, and possibly death. The presence of large walnut trees near a vegetable garden subjects susceptible plants to double jeopardy. The presence of juglone in the soil, plus the competition for light, water, and nutrients creates an extremely stressful environment. Fortunately, not all vegetables are injured by juglone. Corn, beans, onions, beets, and carrots are tolerant of juglone. If the garden plot receives sufficient sunlight, gardeners should be able to successfully grow these crops with timely applications of water and fertilizer.

[verde]

Wow! Thanks for the info.

Verde, how far out are your plants dying?

I think about 30 ft. away. Not everything is affected but 3 apples trees, some blueberry bushes and maybe a rose bush have withered and died for no apparent reason. All the usual reasons were investigated and dismissedl We have several really tall walnut trees.

Must now think about options....

[Owen'nZoe]

Originally Posted by verde

Wow! Thanks for the info.



I think about 30 ft. away. Not everything is affected but 3 apples trees, some blueberry bushes and maybe a rose bush have withered and died for no apparent reason. All the usual reasons were investigated and dismissedl We have several really tall walnut trees.

Must now think about options....

A couple ideas for you, which may or may not work:
- the effects of juglone are supposedly lessened by well-drained soil. If you have heavy clay, you might be able to reduce the concentration of juglone over time by ammending the soil.
- "Gaia's Garden" advocates planting a barrier of juglone-tolerant plants around your walnuts as a barrier, almost like a living fence. If you have enough space, maybe you could try this method, and plant the juglone-susceptible plants on the other side.
- Raised beds can also be effective, as the juglone won't seep up into the raised bed soil. You'll just need to clear out any leaves or nuts that fall into the raised beds.

Walnuts are just such beautiful trees - it'd be a shame to take them down if you don't have to!