Insects that can act as a predatory police force in your garden will help to keep it free of pests throughout the growing season. While you can order beneficial insects online, this can get expensive, and they can occasionally arrive in less than perfect condition. Even if you do release beneficial insects into your garden, they will not stay unless conditions are optimal for them.
You can circumvent both of these problems by planting vegetables and ornamentals that naturally attract beneficial insects to your garden and encourage those already there to stay. For example, leafy greens are feasts for hungry aphids, and should be protected by ladybugs and praying mantises. The latter insects can be attracted to your garden in turn by planting dill and fennel around your lettuce.
There are many more insects that you can attract to your garden which will keep harmful pests at bay, and which are not harmful to humans or plants. They include green lacewings, parasitic wasps, damsel flies, hoverflies, and bees.
The following list explains which plants attract each of these beneficial insects, and has notes on planting and care of each.
Green Lacewings
Green Lacewings are beautifully iridescent insects with brown or green wings. Their larvae do most of the work destroying pests such as mites and aphids. They are sometimes called aphid lions because of this.
| Green Lacewing Attractors | |
| Common name | Planting and Care |
| Dill | Plant in full sun in well-drained rich soil. May need to be staked. Water regularly. Harvest individual leaves as plant matures. |
| Fennel | Plant in full sun in well-drained soil. Water moderately. Survives light frost. Harvest individual leaves as plant matures. |
| Queen Anne’s Lace | Plant in full sun in well-drained, sandy soil. Tolerates some shade and requires little maintenance. Water moderately. |
| Prairie sunflower | Plant in full sun and water moderately. Somewhat drought tolerant. |
| Coriander | Plant in moderate sun as coriander prefers some shade at the hottest part of the day. Water moderately. |
Ladybugs
Ladybugs are a boon to any garden. The larvae are voracious eaters of aphids and mites, and both they and the adults will quickly eradicate infestations of either.
| Ladybug Attractors | |
| Common name | Planting and Care |
| Marigold | Start seeds indoors before last frost. Transplant seedlings two to four weeks after the frost partial to full sun in well-drained soil. Prune flowers regularly to promote robust growth. |
| Fennel | Plant in full sun in well-drained soil. Water moderately. Survives light frost. Harvest individual leaves as plant matures. |
| Butterfly weed | Plant in full sun in well-drained soil. Water moderately. |
| Prairie sunflower | Plant in full sun and water moderately. Somewhat drought tolerant. |
| Yarrow | Plant in full sun in well-drained soil. Yarrow prefers hot, dry conditions and will not tolerate wet soil. |
Parasitic Wasps
Parasitic wasps attack a variety of harmful insects. They do not sting humans. Their stingers have adapted to let the female wasps lay their eggs in the bodies of host insects. When the eggs hatch, they kill the pest insects from the inside out. Straight sci-fi junk. Parasitic wasps control beetles, moths, flies, and other pests.
| Parasitic Wasp Attractors | |
| Common name | Planting and Care |
| Cosmos white sensation | Plant in full sun in well-drained soil after danger of frost has passed. Water moderately. |
| Parsley | Plant in sun or partial shade in well-drained, rich soil. Water moderately. |
| Zinnia | Plant in full sun in soil that is amended with compost. Water moderately. Deadhead to prolong flowering. |
| Lavender globe lily | Plant in full sun in well-drained soil. Water moderately. |
| Yarrow | Plant in full sun in well-drained soil. Yarrow prefers hot, dry conditions and will not tolerate wet soil. |
Praying Mantis
Praying mantises are a top predator in the garden, and one or more will patrol the length of a moderately-sized garden, wreaking havoc on any pests. These are a bit harder to attract unless there is already an endemic population in your area, so you may want to consider purchasing one or two mantis egg capsules online. Mantises require the presence of trees or shrubs. Good candidates are maples, pine trees, and any green, leafy shrubs that will attract insects for the mantis to hunt.