9 Beneficial Insects Every Flower Garden and Flowering Shrubs Need

Did you know that, in addition to sunshine and water, bugs are the MVPs of every thriving flower garden? Yes, bugs ... but they've got to be the right kind of bugs.

Beneficial insects are a gardener's best friends, whether you're growing a vegetable garden, or are helping to grow healthy flowers, plants, and shrubs with gorgeous blossoms. These insects accomplish many tasks that otherwise would be difficult for you, like pollinating flowers, devouring pests, and parasitizing "bad bug" insects. Ideally, you should invite all three types of beneficial bugs to your backyard. If you are wondering where to begin, start with the bugs discussed below — three pollinators, three predators, and three parasitoids — essential for any flower garden. You can attract them by growing a wide range of diverse flowers, including wildflowers and herbs, and offering a fresh water supply.

1. Pollinator: Honey Bees

Honey bees, known and loved for the sweet honey they produce in their hives, are the most important pollinator on the planet. Pollinators carry out the profoundly valuable job of transferring pollen from the male parts of a plant to the female parts, allowing the plants to form seeds that maintain the species. Over 200,000 plant species worldwide depend on pollination to reproduce.

Honey bees accomplish the vast majority of the pollination of edible plants in the country, up to 80 percent of the vegetables, fruits, nuts, and grains produced in the United States. But they also pollinate flowers and flowering plants, transferring pollen from the anthers of one flower to the ovules of another. This is how the flowers in your garden produce seeds to reseed themselves or grow new plants.

2. Pollinator: Bumble Bees

Something about the golden bumble bee makes it seem more friendly and appealing than many other insects. They are plump, rounded insects that look like they are made of fuzz. While they do not produce honey that can be used commercially like the honey bee, they are very important pollinators of flowering plants.

Bumble bees are important in a flower garden because they pollinate types of flowers that honey bees do not. For example, they are adept at pollinating flowers with long, narrow corollas, like trumpet vine flowers. They also are vital pollinators in cooler regions since they are able to fly in chillier weather than honey bees. These bees usually forage within a few miles of their underground nest.

3. Pollinator: Butterflies

Bees are the most acclaimed pollinator insects, perhaps because they do more pollination of commercially important agricultural crops than any other insect. But butterflies are also pollinator stars of flower gardens, especially those containing wildflowers. These graceful insects flit from flower to flower, pollinating a wide variety of blossoms in one day. They prefer big, vibrantly colored flowers that offer a place where these long-legged insects can land, and only pollinate flowers that open during the day.

Butterflies may carry less pollen than bees, but they carry it farther. Bees move quickly from flower to flower on one plant, then rush back to the hive to provide food for the brood. A butterfly takes its time, using the nectar it gathers at one flower to fuel its flight to the next flower sometimes a good distance from the first. In its own, leisurely way, the butterfly is performing cross-pollination, mixing the genes of plants to promote genetic diversity.

4. Predator: Aphid Midge

Aphids are generally recognized as one of the worst nuisance bugs in a flower garden. These tiny insects seem to find their way into every flower garden and appear on almost every type of plant. They grow no bigger than a 1/2 inch long and are soft-bodied but tough and durable. They can survive in almost any zone, multiply quickly, and feed on plant juices, damaging leaves, stems, buds, flowers, fruit, and even roots.

Who can help you with these bad bugs? Although ladybugs are more famous, you'll find that an even better predator is the aphid midge. It's a predator bug, meaning that it takes care of pest bugs in the simplest way possible: by eating them. Aphid midge begin life as eggs, then develop into larvae, tiny slug-like creatures that mature into very small (1/8 inch long) black flies. The young larvae and the long-legged adult flies chow down hardily on more than 60 species of aphids after paralyzing them with toxic saliva.

5. Predator: Hover Fly

Another very common flower-garden problem bug is the caterpillar. Caterpillars come in different shapes and sizes, but all of them need to eat, and most of them eat your plants. Some particularly damaging types of caterpillars can attack and overwhelm flowering plants and shrubs. While you won't want to apply chemicals in the garden to kill caterpillars, hover flies (also called syrphid flies) can go a long way when it comes to controlling the pest.

If you mistake a hover fly for a yellow jacket, you won't be the first. These bugs usually have bright markings of yellow-orange and black. Their coloration looks similar to yellow jackets but the hover fly has just two wings. Plus it won't sting. Moreover, they help out both as pollinators as well as bad-bug predators. The hover fly adults won't attack pests, since they eat nectar. But their larvae are voracious predators. They crawl around on flower foliage searching for prey. They regularly take out caterpillars, as well as aphids, beetles. and thrips, sucking the innards out in juice form.

6. Predator: Spidermite Predator

Another insect pest that lurks in flower gardens is the spider mite. Both nymphs and adults produce a recognizable webbing that alerts you to their presence. The bugs feed on the underside of leaves, causing yellowing and reducing the photosynthetic area of the leaf. The plant stops growing and can die. While you can find pesticides to deal with these destructive flower-garden bugs, spider mites have some natural enemies that can step in to take care of the situation if you don't use pesticides.

Beneficial Insects for Flowers: Hover Fly
credit: Alchetron

The most important predators of the spider mite are the predatory mites, called spidermite predators. These predatory mites are also tiny, about the same size as the spider mites, but their legs are longer and they move quicker. Predator mites don't feed on plants so they never become pests themselves. If they can't locate any spider mites to eat, the predators move elsewhere. According to experts, one predator mite can take out 10 spider mites per day. If you are able to get these predator mites established on perennial plants in your flower garden, they will reproduce there and offer biological control indefinitely.

7. Parasitoids: Tachinid Flies

Parasitoids are also good bugs in the garden. They don't take out bad bugs by eating them, but instead they lay eggs on or in the bad bugs. Larvae eventually emerge from those eggs, and larvae emerge hungry. They feed on the host insects, eating them alive.

One great parasitoid for a flowering garden is the tachinid fly. It lays its eggs on caterpillars, and the larvae burrow into the bugs, destroying these garden pests from the inside. Their prey includes the cutworm, the nemesis of many gardeners.

Cutworms are fat worms about an inch long and either gray or black. Rarely seen during the day, these worms become active — and destructive — at night, eating young flower seedlings and transplants throughout North America. The cutworms keep to the ground and chew through the stems at ground level, usually killing the plant. If a seedling is small enough, cutworms can eat it entirely.

Tachinid flies also kill Japanese beetles. Those are the metallic green insects that munch your rosebuds and other flowers.

8. Parasitoid: Trichogramma Wasps

Not all wasps are big and angry. One tiny wasp, the Trichogramma wasp, is definitely a bug you want in your flower garden. Although it is truly small and looks like a small housefly, the Trichogramma pretiosum wasp knows how to kill. It parasitizes some 200 pest insects including armyworm, bagworm, European corn borer, peach borer, squash borer, cankerworm, alfalfa caterpillar, cutworm, corn earworm, wax moth, tomato hornworm, cabbage looper, and codling moth.

Beneficial Insects for Flowers: Trichogramma Wasps
credit: Garden Simply

Unlike the Tachinid fly, the Trichogramma wasp doesn't look for adult pests on which to lay its eggs. It lays its eggs in the eggs of the undesirable insects after using its sense of smell to determine whether the host is suitable. The parasitic wasp larva kills the host eggs before they even get to the larval stage. That means that the bad bugs never live to eat your plants.

9. Parasitoid: Aphid Parasitoid

Another wasp that lays eggs on bad bugs is named the aphid parasitoid. Truly tiny, aphid parasitoids are only about 1/10 inch long at their biggest. Like other wasps, they are slender with a pinched in "wasp" waste.

Beneficial Insects for Flowers: Aphid Parasitoid
credit: R. Berg

These beneficial bugs live in or near aphid colonies and female wasps lay their eggs inside the pests. In time, the eggs hatch into tiny white grub. As the larvae feed on the aphids, they kill them, but turns the bodies of the bugs into sorts of mummy, papery, swollen and dark in color. As the larvae turns into wasps, they chew holes in the mummies to fly away. And don't worry, the adults aren't dangerous. They feed on and can be attracted by nectar from little blossoms like anise, caraway, dill, parsley, mustard, and white clover.


Teo Spengler

Teo Spengler

From Alaska to California, from France's Basque Country to Mexico's Pacific Coast, Teo Spengler has dug the soil, planted seeds and helped trees, flowers and veggies thrive. A professional writer and consummate gardener, Spengler has written about home and garden for Gardening Know How, San Francisco Chronicle, Gardening Guide and Go Banking Rates. She earned a BA from U.C. Santa Cruz, a law degree from U.C. Berkeley's Boalt Hall, and an MA and MFA from San Francisco State. She currently divides her life between San Francisco and southwestern France.