Question: Are there certain plants I can grow to encourage beneficial insects in my garden?
Beneficial insects include a wide range of insect predators and parasites. These include not only the well-known ladybugs and praying mantids, but a great many smaller insects, such as lacewings, syrphid flies, tachinid flies, braconid wasps and trichogramma wasps, to name just a few. They are the natural controls for many garden pests, from aphids to tomato hornworms.
While the larvae feed on insects, most of the adults rely at least in part on the nectar and pollen produced by flowering plants. Several plant families are particularly important food sources. These include the carrot family (Apiaceae). Consider growing Queen Anne's lace (Daucus carota) or bishop's flower (Ammi visnaga). The daisy family (Asteraceae) is another good source, with plants such as yarrow (Achillea spp.), blanketflower (Gaillardia spp.), coneflower (Echinacea spp.), coreopsis, feverfew (Tanacetum parthenium), and goldenrod (Solidago spp.). The mustard family (Brassicaceae) supports beneficials, with basket-of-gold (Aurinia saxatilis) and sweet alyssum (Lobularia maritima). A good number of edible crucifers do, too, if they are allowed to bloom. These include arugula, Swiss chard, pak choi, and tatsoi. Finally, several members of the figwort family (Scrophulariaceae), including stiff beardtongue (Penstemon strictus) and spike speedwell (Veronica spicata), provide sustenance.
As you can see, it is possible to assemble quite an attractive flowerbed with the goal of supporting biological pest control. For maximum benefit, try to maintain overlapping bloom periods to provide the beneficial insect adults a steady supply of food.
This post is excerpted from the July/August 2003 issue of Horticulture.
Image Credit: Wikimedia Commons
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