Weed, Insect, and Animal Relationships
“Weed” control—The growth of beets, members of the
cabbage family, and alfalfa is slowed down signicantly
by the presence of weeds. To minimize the weed
problem for sensitive plants, you can grow other plants
during the previous season that discourage “weed”
growth in the soil in the current season. Two such plants
are kale and rape. Another example is the Mexican
marigold (Tagetes minuta).^6 “In many instances it has
killed even couch grass, convolvulus (wild morning
glory), ground ivy, ground elder, horsetail, and other
persistent weeds that defy most poisons. Its lethal action
works only on starch roots and has no e5ect on woody
ones like roses, fruit bushes, and shrubs. Where it had
grown, the soil was enriched as well as cleansed, its
texture was rened, and lumps of clay were broken
up.”^7 Some care should be taken when using this
marigold, however, since it might also kill vegetable
crops and it does give o5 toxic excretions. Tests need to
be performed to determine how long the in'uence of
these excretions stays with the soil. But to cleanse a soil
of pernicious weeds and thereby get it ready for
vegetables, Tagetes minuta appears to be a useful plant.