Marigolds are among the flowering plants that help repel unwanted insect pests.
Some insects, like bees and butterflies, are highly desirable garden visitors. Others are less popular, with mosquitoes among the most annoying and potentially dangerous. A number of flowering plants have some degree of repellent effect on mosquitoes and other insect pests. In most cases, however, it is the leaves rather than the flowers that have the greatest repellent power. For humans concerned with mosquito and other insect bites, it is not enough to have a repellent plant nearby. Effective protection generally involves rubbing the leaves, or remedies made from the leaves, directly on the skin. Does this Spark an idea?
Repellent Daisies
Marigolds (Tagetes) are an old garden favorite and a member of the daisy or Compositae family. Planted among tomatoes or other vegetables, the marigold's strongly scented leaves and flowers repel flies and other insects. They are easy to grow, thrive under many conditions and often reseed in the garden. Another daisy family member with an equally strong smell is tansy (Tanacetum), which deters ants. Unlike other members of its family, tansy's blossoms have no petals, only centers composed of tiny flowers. One tanacetum species, Tanacetum cinerariifolium, was the original source of the insecticide pyrethrum.
Citrus and Citronella
A grass species native to Sri Lanka, Cymbopogon nardus, also known as citronella grass, is cultivated in Florida, California and other tropical areas as a source of the fragrant, lemony citronella oil that is highly touted as a mosquito repellent. It is used in candles and other repellent products. Two other citrus-scented plants, Collinsonia canadensis (citronella), which is a member of the mint family, and Pelargonium x citrosum (orange geranium), which is a member of the geranium family, have reputed mosquito-repellent powers. Leaves of all three plants must be rubbed on the skin to have an effect.
Other Mints
Strongly scented mints, like horsemint (Mentha longifolia) and catmint (Nepeta), have insect-deterrent properties. Blue-flowered catmint makes a good companion planting for roses and is reputed to help deter aphids, which suck the juices from young growth. Many mint family members are effective at deterring animal as well as insect pests in the garden.
Other Citrus Remedies
Lemon balm (Melissa officinalis) is a lemon-scented mint family member with tiny white flowers. The crushed leaves are effective at repelling mosquitoes. Another mint relative, lemon thyme (Thymus x citriodorus) bears tiny lavender flowers and strongly scented leaves. The green-leafed and variegated forms are attractive garden plants and help repel mosquitoes if applied to the skin. As with all repellents, it is wise to perform a "patch test" -- applying the crushed leaves to a small area of skin -- before using the plant more widely.
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