Photo by Rachael Brugger
Whether flea beetles are making lace out of your eggplants or tomato hornworms are stripping your favorite slicing tomatoes, we’ve all battled insect pests in the garden. Fortunately, besides handpicking, relying on organic insecticidal soaps or employing lightweight floating row covers, organic gardeners have another weapon in their integrated pest management arsenal: companion planting. With the right combinations of companion plants and decoy plants, you can rid your garden of destructive pests and enjoy your favorite vegetables with fewer worries.
How Does Companion Planting Work?
By planting particular plants near one another, you can keep some insects at bay. Some companion plant combinations drive insect pests away, while others attract beneficial insects that, in turn, help keep the numbers of harmful insects in check. Still other combinations work to "trap” or isolate certain kinds of insects. Some companion-plant combinations can even do all three!
For the best results, you should have a good mix of perennial herbs and flowers along garden borders and interspersed with your vegetable crops. While it’s true that companion planting won't guarantee pest-free produce, it certainly can help to make a dent in the numbers of problem insects.
Common Companion Plants
Marigolds and pot marigolds (aka calendula) re some of the most well-known companion plants. The scent of marigolds deters cabbage maggots, Mexican bean beetles, aphids and many other pests, and calendula turns off tomato hornworms and asparagus beetles. Plant both along crop rows and between plants for a little extra color and added insect protection.
Other herbs, while be delicious additions to the dinner table, also double as great companion plants. For trouble in the cabbage patch, try thyme, which is thought to ward off cabbage worms, and peppermint, to help keep cabbage butterflies away. Plant catnip amongst your potatoes, as it repels the pesky Colorado potato beetle, or near your cucumbers and eggplant, as it drives off flea beetles and squash bugs, too. Nasturtiums, likewise, can deter squash bugs, assorted beetles and some types of aphids.
Interestingly, some of the very plants that are repellent to insect pests—like peppermint and thyme—are quite attractive to beneficial insects that feed on aphids, mealy bugs and other troublemakers.
If you have a particular insect foe, use the companion plants below to keep them at bay:
Sometimes found feeding on young cabbage heads, on the undersides of lettuce or spinach leaves, or even on sweet corn tassels, aphids are among the most common insect pests. Thankfully, the larvae of green lacewings and ladybugs, as well as adult ladybugs, will eat large numbers of these soft-bodied freeloaders. Plants with clusters of tiny flower heads, like yarrow, coriander, Queen Anne's lace, fennel and dill, will attract both ladybugs and green lacewings.
Many types of caterpillar wreak havoc on cabbage, as well as broccoli, cauliflower, Brussels sprouts and assorted greens. The good news is that you can enlist predatory wasps to do them in. To attract the tiny, stingless helpers, try many of the same plants that appeal to lacewings and ladybugs along with lemon balm, parsley, chamomile, peppermint and catnip.
While eggplant, tomatoes, potatoes and beans often fall victim to leafhoppers, leafhoppers, in turn, can fall prey to the larvae of hover flies, which are attracted to many of the same plants as predatory wasps. Hover flies also will gravitate to English lavender, buckwheat, statice and sweet alyssum.
You can protect your produce in one other particularly tricky way. By growing "trap” crops—plants well-known to attract specific insect pests—alongside any plants you wish to protect, you can divert attention away from your veggies and isolate the damage that problem insects can do.
Scented Geraniums and Four O'clocks
While Japanese beetles can be especially troublesome, you can draw them away from your green beans or those prized roses by planting scented geraniums and four o'clocks nearby. Although the adult beetles love to eat both, the flowers of scented geraniums and the leaves of four o'clocks happen to be toxic to them. Although it won't kill them, borage is also said to be another good Japanese beetle lure. Should you plant it as a trap crop, be prepared to handpick the insects daily to knock down their numbers.
Another popular trap crop, nasturtiums will attract large numbers of black aphids; to control their populations, you can handpick regularly or periodically treat with an organic, insecticidal soap. For very heavily infested plants, simply rip them out and discard well away from the garden.
Planting an extra row or two of whatever vegetable you wish to grow can also work to trap and isolate insect pests, as most insect pests stay on or near the host plants from which they originally hatched. Mixing low-growing herbs in between individual vegetable plants and between rows of tomatoes, potatoes and other crops can further help to throw insects off the trail of potential host plants.
Of course, despite our best efforts, it's normal to experience some losses in the garden, though with the right combinations of companion and trap plants, we may not have to share as much of the harvest with insect pests.
About the Author: Susan Brackney writes about gardening, beekeeping, environmental affairs, the natural world and more from her home in Indiana.