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Black Walnut Trees & Poison

Black walnut trees are poisonous to plants. The trees can also have negative health consequences for animals and humans.

  1. Black Walnut Tree

    • The Black Walnut tree (Juglans nigra) is found throughout the eastern United States to the Missouri river. The trees grow well in moist soils and are resistant to disease and insects. Black walnut trees have edible nuts and the wood is used for furniture.

    Juglone

    • Black Walnut trees produce the toxic chemical juglone (5 hydroxy-1, 4-napthoquinone). The chemical, according to The University of Georgia College of Agricultural and Environmental Sciences, originates inside the trees as non-toxic prejuglone. Injury to the tree from other plant roots , or insects, or humans cutting the tree, brings prejuglone to the bark and oxidizes the chemical into juglone.

    Black Walnut Trees And Effects On Plants

    • Black Walnut trees can be lethal to some plants. Annuals, fruits and vegetables are vulnerable. Herbaceous perennials are also at risk. Juglone can damage several varieties of shrubs and trees. Black Walnut leaves should not be used for compost nor should any part be used for mulch because toxic chemicals remain in the decaying foliage. Several varieties of trees, shrubs, herbaceous perennials, and flowers can withstand juglone.

    Black Walnut Trees And Horses

    • Black Walnut shavings should not be used as horse bedding. The sawdust can poison horses. The Ontario Ministry of Agriculture Food and Rural Affairs website states that these animals can develop laminitis, a foot inflammation, from the shavings or respiratory distress from pollen. Remove the poisoned shavings or stable the horses away from Black Walnut trees. Consult a veterinarian for appropriate treatment.

    Black Walnut Trees And Humans

    • Juglone poisoning can affect humans. Black Walnut pollen can cause respiratory distress. You must take care when cutting down trees because sawdust, according to WorkSafe Alberta, can cause dermatitis, rhinitis (runny nose) and possible asthma. Always wear protective gear when cutting trees and consult with a doctor if you have symptoms.

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