Destructive insects often locate their food by smell. Many plants, especially culinary herbs, produce strong scents which may confuse insect pests looking for a host plant to feed on. Garden vegetable plants such as garlic, onions, chives, and herbs such as catnip, horehound, wormwood, basil, tansy, and mints all produce scents that seem to repel insects or mask the scents that attract insects. A certain level of insect protection can be achieved by carefully interplanting some of these as companions to vegetables.

Many insects are helpful because they eat or parasitize harmful insects. Most species of wasps and spiders are beneficial, as are ground beetles, praying mantis, ladybugs, pirate bugs, and several species of flies. It is possible to attract beneficial insects by planting flowers near the garden. Dill, parsley, carrot, coriander, angelica, and parsnip feature flat-topped clusters of small flowers that have strong fragrances. They seem to attract large numbers of beneficial insects--particularly predatory wasps and flies--making them good candidates for companion planting.

How Can Home Gardeners Utilize Companion Planting?

Avoid monoculture. A 100-foot-long row of broccoli presents a large target for a cabbage moth flying by, but the same number of cabbage plants scattered over several thousand square feet and interplanted with other crops is less obvious and attractive to the insect. Pests which routinely plague large, commercial plantings of crops, may never be a problem in the diversified home garden.

To avoid killing beneficials inadvertently, learn to recognize them as well as the troublesome pests. Less than one percent of insects are garden pests.

To attract beneficials, plant dill, marigolds, chives, onions, parsley, basil and other flowers throughout the garden. Allowing parsley, carrot and celery to remain in the ground over the winter will produce flowers the next year and attract helpful beneficial insects to control the bad insects.

More extraordinary help here.

For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service