Enticing Predators to Patrol Your Garden

Winter is a good time to begin planning which native flowering plants and herbs to cultivate in your yard this spring to create a haven for beneficial insects

01-15-2010 // Janet Marinelli

Robber fly by Bud Hensley

IT'S EASY TO LOVE BUTTERFLIES. But for many gardeners, attracting these beautiful pollinators is where the infatuation with insects begins and ends. Invite carrion beetles and assassin bugs to a flower border or vegetable patch? Only the intrepid dare go there.

Yet there are good reasons to create a backyard buffet for these and other so-called beneficial insects (robber fly, left). They are the tigers and barracudas of the insect world, preying upon many of the organisms that ravage prized garden plants. So many homeowners have pest problems largely because their yards are not inviting to the predators and parasites that in natural ecosystems keep pesky creatures in check.

Although a number of biological pest controls—the fancy term for beneficial insects—are sold at local nurseries and mail-order suppliers, the most effective way to entice predators to patrol your yard is to grow their favorite flowers. Winter, when you’re perusing the pages of nursery catalogs and dreaming of spring, is a great time to look for the blooms these creatures love best: asters, coneflowers and other daisylike native wildflowers, as well as popular culinary herbs such as dill and parsley that produce inverted parasol-shaped inflorescences.

One of the extra benefits of welcoming beneficial insects to your garden is that it provides you with a fascinating new world of wildlife to discover right outside your door. Some of these species have an ethereal beauty, like the delicate green lacewing. Other predators look the part, including the spined soldier bug, which is shaped like a shield with a conspicuous spine on each shoulder, armorlike plates for wings and a sharp beak it uses to impale its victims.

Some beneficial organisms are true predators that catch and eat other insects, mites and other garden pests. Among them are beetles and harvestmen, or daddy longlegs. Typically, the adults sup on pollen and nectar from favored flowers, while the larvae do the heavy-duty pest control. Other beneficials are parasitoids, which have immature life stages, usually as larvae that develop on or within a victim, ultimately killing it. These include several types of mini-wasps, which are harmless to humans, and tachinid flies, which are about the size of houseflies.

Following are a few of the ways you can lure a diversity of both predators and parasitoids to your garden:

Grow as many as possible of the herbs and wildflowers native to your region with blooms that are tailor-made for beneficial insects. (See list below for plant recommendations.)

Mingle these predators’ favored flowers in your planting beds, or mass them to create large predator patches in the parts of your garden that have the biggest pest problems.

Select native plants with different flowering times so that a predator-friendly flower is always in bloom to provide the beneficial insects with nutritious pollen and sweet nectar.

Combine predator-friendly plants of various heights to create the kind of structurally diverse habitat that will attract a diverse array of beneficial species to your garden.

Don’t remove the fallen leaves from your planting beds. A healthy layer of leaf litter provides habitat for beetles, spiders and other important predators.

Identify before you squish or swat. Some beneficial insects, such as lady beetles, are instantly recognizable, but others are unfamiliar and a few are almost microscopic. A number of useful online guides are available to distinguish the good creatures from the pests, including Cornell University’s Biological Control: A Guide to Natural Enemies in North America.

• Not all beneficial organisms are small insects. Many birds and bats will gladly dine on pest populations on your property. Provide native trees and shrubs where the animals can rest and raise young. Installing bat or bird boxes is another way to help entice the creatures to take up residence in your yard.

Lay off the pesticides, which will cause as much harm to the beneficial insects as to the harmful ones. To enable predators and parasites to take over pest control, you’ll need to tolerate some minor infestations. Normal populations of “bad guys” are a necessary food source for the beneficials and help keep them in your yard. However, this is a small price to pay for a healthy garden—and a whole new realm of nature to explore.

New York journalist Janet Marinelli writes frequently about native plants for this magazine. You can visit her blog on natural gardening and sustainable living at www.janetmarinelli.com .


The Best Blossoms for Beneficial Insects

Studies suggest that native composites, wildflowers with daisy-shaped blooms, are champions at attracting beneficial insects. North America is home to a large variety of spectacular composites. Some of the most widely distributed include:

Asters: Different types are found in all 50 states. Named after the Latin word for “star,” asters come in blues, purples and pinks, all with a yellow center.

Goldenrods: Easily identified by their golden inflorescences with dense masses of tiny flowers, goldenrods are often difficult to tell apart and represent some of the most ubiquitous composites.

Coneflowers: In colors from purple to gold, typically with brown to orange centers, coneflowers are found from coast to coast.

Tickseeds: Also known as coreopsis, tickseeds are native to all but three states—Alaska, Nevada and Utah. They often are partly colored yellow and have petals with notched tips.

Sunflowers: Wild relatives of cultivated sunflowers, which are known for their huge flowerheads, grow throughout the continental United States. Often yellow, they also occur in shades of orange, chestnut and maroon as well as combinations of these colors.

Buckwheats and milkweeds: These plants also are magnets for good bugs. So are culinary herbs with distinctive flower clusters called umbels that resemble little upside-down umbrellas. Some umbelliferous herbs of varying heights include coriander, chervil, fennel, flat-leafed parsley, dill and lovage.


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