The black walnut tree manufactures a substance that is a
natural insecticide according to experts at the Texas State
University in Austin.
American black walnut tress contain a tannic acid chemists
call juglone. The reddish yellow substance leaches from
leaves, and some believe exudes from roots, or transfers
from branches and foliage to the roots. Tree physiologists
agree that roots of other plants that come in contact with
those black walnut tree roots die--even other black walnut
Juglone is sometimes washed out of the still green walnuts
during late summer or even autumn rains. The growth of
plants 60 to 80 feet away are inhibited by the juglone. The
substance affects plants of various families. Studies have
found that tomatoes, alfalfa, potatoes, apples,
blackberries, rhododendron, mountain laurel and pine trees
are all affected.
According to a professor and extension forester at Iowa
State University, juglone is known to repel various garden
insects. Just by placing branches of the tree around the
house and under furniture dog and cat owners are amazed to
find that their pets have fewer fleas.
For more information on natural flea control:
For more information on natural garden products:
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Author: Marilyn Pokorney
Freelance writer of science, nature, animals and the
Also loves crafts, gardening, and reading.