Which Plants Battle Bugs?

A reader asks the Green Guide:
Can you suggest some plants that would control bugs and mosquitoes around the deck and yard?

The Green Guide responds:
Given the neurotoxic and carcinogenic ingredients of most bug sprays, we're not surprised that so many of our readers ask about safer alternatives-particularly some you can plant in the yard. There are many accounts of plants keeping bugs at bay, and a handful of them are true: Bay leaves really do deter cockroaches; Australian tea tree oil works well against ants, mites, and roaches; and crushed citronella, catnip, lemon thyme and wild marigolds all have some mosquito-repelling properties.

But the whole truth is that just growing these plants in pots won't eliminate all your pest problems . Although many plants contain insect-repelling chemicals that protect them from pests, these power plants don't produce and emit enough of them to keep nearby people and pets pest-free. To do that, you'll need the plants' essential oils and a little help from some friends.

The real benefit of plant-based pest control comes from the beneficial bugs and insect-eating animals the plants attract. These pest-eaters include some birds (bluebirds, chickadees and hummingbirds are a few), bats, lizards, ladybugs, praying mantises, dragonflies, spiders, green lacewings, hoverflies, parasitic wasps and predatory mites. They will flock to a healthy, balanced ecosystem to fight the bug battle for you. Choose a varied mix of plants, with edibles alongside flowering plants like clovers, marigolds, and members of the mustard, sunflower, celery and carrot family, whose nectar helps feed beneficial bugs and birds. Keep these plants healthy year-round if you can, so beneficial insects have supplementary food and dependable shelter as they control bugs throughout the year.

Be sure to make your deck and yard inhospitable to unwanted bugs as well. Decomposing material will draw pesky flies, overwatered lawns frequently fall prey to grubs, and even the smallest puddle of standing water can become home to mosquito larvae within as little as three days. Bird feeders and baths that help attract insect-eating birds must be cleaned and restocked frequently to prevent attracting mosquitoes and rodents. Starting and maintaining a balanced backyard ecosystem may sound overwhelming, but so long as your garden is diverse and well tended, the good bugs will come. And if they don't, Arbico Organics sells starter kits of prepackaged beneficial insect eggs ($7.60 and up; www.arbico-organics.com), just in case.

For personal protection, there are greener alternatives to toxic DEET- and permethrin-based insect repellents. Find a plant-based insect repellent in our recently updated Insect and Mosquito Repellents Buying Guide.

For more information on pests and managing them naturally:
www.ipm.ucdavis.edu/PMG/menu.homegarden.html
www.beyondpesticides.org/alternatives/factsheets/index.htm