Walnut tree produce a chemical substance known ashydrojuglone . It is found in every part of the tree . Hydrojuglone by itself is harmless and odorless . However , when oxidized by compounds in the air and grease , hydrojuglone is transformed into a toxic allelochemical screw as juglone . Allelochemicals are secretions that fundamentally poison some types of nearby plant by inhibiting physiological processes , such as sprouting , growth and food and piss uptake . While all type of walnut trees grow juglone , only the contraband walnut tree tree typically produces quantity sufficient to impact skirt plants . Juglone - tender plants placed near pitch-black walnut will necessarily yellow , wilt and fail .

Toxicity Range

The greatest concentration of juglone occurs in walnut ascendant , buds and fruitcake hulls . therefore , the highest probability of plant toxicity is within the canopy of black walnut tree Tree , where roots , fall leaves and decay nut hulls are ever - present and concentrate . However , plants growing within 1/2 column inch of a undivided black walnut tree Sir Herbert Beerbohm Tree stem are also at hazard of happen juglone . This contact may happen beyond the tree diagram canopy , peculiarly in large tree specimen .

Symptoms of Juglone Sensitivity

Members of the Solanaceous family , which includes tomato plant , eggplants and capsicum , are some of the plants most adversely affected by juglone . symptom of juglone sensitivity include a progression of leaf yellowing , drooping and eventual plant death . In general , juglone is nontoxic to human , but it may cause a mild allergic symptoms in someone who are sore to the chemical , peculiarly during springtime .

Garden Design Implications

site any juglone - sensitive works outside of the toxic zona of smutty walnut tree trees . With young tree , wear a root zone of about twice the height of the tree . This geographical zone will continue to increase with age . The toxic zone of fledged trees can gallop up to 80 fundament from the Sir Herbert Beerbohm Tree proboscis . If this degree of spacing is not workable , consider put other planting in container or raised planting bed . Alternatively , locate other plant on the other side of a lasting barrier , such as a drive , to minimize potential contact with toxin .

Toxicity Control

Add organic textile to soil . This will increase the population of soil microbials and meliorate grime drainage capacity , which in tour will metabolize toxins . Routinely rake up fallen leaves , yield or any other human body of rubble from under black walnut trees , but stave off using this material as compost or mulch for other plants . In general , tree remotion is not advised unless it is attach to by total root remotion as well . Any theme not removed from the grime can continue to emit juglone until they completely decay , which could take long time .

References

…