QuestionDoes the green black walnut hull also contain the same ingredient that causes anaphylactic shock in humans when they eat the actual nut? No one can seem to answer this. I bet you can!
AnswerI would not think so unless the person is allergic to nuts (peanuts, walnut, etc.). Black Walnuts produce a toxin called "juglone" in all parts of the tree.
It is an anti-respiratory compound with a phenolic ring. It probably evolved to deter insect pests, not plants or humans. Fishermen have used ground up walnut hulls to attract fish to the surface of the water; the
juglone slows fish respiration and the fish come to the surface to breathe.
While many plant grow well in proximity to black walnut, there are certain plant species whose growth is hindered by this tree. The type of relationship between plants in which one produces a substance which affects the growth of another is known as "allelopathy."
Awareness of black walnut toxicity dates back at least to Roman times, when Pliny noted a poisoning effect of walnut trees on "all" plants. More recent research has determined the specific chemical involved and its mode of action. Many plants have been classified through observation as either sensitive or tolerant to black walnuts.
The Source of Toxicity
Plants adversely affected by being grown near black walnut trees exhibit symptoms such as foliar yellowing, wilting, and eventual death. The causal agent is a chemical called "juglone" (5 hydroxy-1, 4-napthoquinone), which occurs naturally in all parts of the black walnut. Juglone has experimentally been shown to be a respiration inhibitor which deprives sensitive plants of needed energy for metabolic activity.
The largest concentrations of juglone and hydrojuglone (converted to juglone by sensitive plants) occur in the walnut's buds, nut hulls, and roots. However, leaves and stems do contain a smaller quantity. Juglone is only poorly soluble in water and thus does not move very far in the soil.
Since small amounts of juglone are released by live roots, particularly juglone-sensitive plants may show toxicity symptoms anywhere within the area of root growth of a black walnut tree. However, greater quantities of juglone are generally present in the area immediately under the canopy of a black walnut tree, due to greater root density and the accumulation of juglone from decaying leaves and nut hulls. This distribution of juglone means that some sensitive plants may tolerate the amount of juglone present in the soil near a black walnut tree, but may not survive directly under its canopy. Alternatively, highly sensitive plants may not tolerate even the small concentration of juglone beyond the canopy spread. Because decaying roots still release juglone, toxicity can persist for some years after a tree is removed.
