Flowers That Attract Beneficial Insects: How to Plant an Insectary Border

An insectary planting is a group of flowers grown to feed the insects that eat garden pests. Many of those helpers, such as lacewings, hover flies and tiny parasitic wasps, live on nectar and pollen as adults, and lay their eggs where pests are. University of California IPM explains that without these flowers, natural enemies are less abundant or live shorter lives. This guide covers which beneficial insects you are feeding, the plant families that work best (from Penn State and Clemson Extension), how to lay out a flower border or strip, a fast filler crop, and what keeps an insectary working.

The beneficial insects you are feeding

• Lady beetles eat aphids and other soft-bodied pests as larvae and adults. Penn State notes that aster-family flowers attract them.
• Lacewings: the larvae are aphid predators. UC IPM notes that adult green lacewings, like many parasites, feed only on pollen and nectar.
• Hover flies (syrphid or flower flies): their larvae eat aphids. Penn State notes that the adults look like small yellowjackets but do not sting.
• Parasitic wasps and flies: tiny, harmless to people, and they lay eggs in pests such as caterpillars and aphids. Clemson Extension notes that they need small flowers, such as alyssum, cilantro, parsley, dill, buckwheat and fennel, because they cannot reach nectar in deep blooms.
• Ground beetles, soldier beetles and assassin bugs round out the list of predators Clemson names.

The best plant families for beneficial insects

Penn State Extension groups good insectary plants by family. Pick a few from the first two rows and you have the core of a border.

Clemson Extension, by contrast, lists sweet alyssum among the small flowers to grow in a vegetable garden. If you grow broccoli, cabbage or other mustard-family crops, our companion planting for pest control guide explains how mustard-family trap crops are used for flea beetles.

Keep something in bloom from spring to fall

Both Penn State and UC IPM stress timing: a mix of plants that flower one after another keeps food available all season, so beneficial insects stay and build up. A simple way to plan it:

1. Early.

   Cool-season herbs that flower as they bolt, such as cilantro and dill, plus sweet alyssum.

2. Early to midsummer.

   Yarrow, coreopsis and a sowing of buckwheat, which flowers within weeks.

3. High summer.

   Cosmos, sunflowers, signet marigolds and blanketflower.

4. Late summer and fall.

   Goldenrod, asters and a second sowing of cilantro or dill as the weather cools.

Let a few vegetable-garden herbs flower too. Bolting cilantro, dill and parsley are some of the best small-flowered insectary plants you can grow, as our cilantro and dill guides explain.

How to plant an insectary border

• Keep it close. UC IPM notes that the benefit of insectary plants decreases with distance from the flowers, so plant them along bed edges, at the ends of rows or in clumps inside the garden rather than in a far corner.
• Border, strip or clumps. UC IPM describes insectary plants grown as a border around crops, or interplanted in rows or clumps. In a small garden, a 1- to 2-foot strip along one side of each bed, or a few clumps at the corners, is enough to start.
• Add perennials. Penn State notes that permanent plantings such as yarrow, coreopsis and goldenrod give beneficial insects places to overwinter, so the border keeps working year after year.
• Offer water. Penn State suggests a shallow dish of water with pebbles or stones for insects to land on.
• Mind the tall ones. Put sunflowers and cosmos on the north side, so they do not shade vegetables; see what to plant with sunflowers.

A fast filler: buckwheat

Buckwheat is a quick way to put flowers in an empty bed. UW–Madison Extension's guide to home-garden cover crops says it germinates readily, grows quickly and flowers early, and attracts bees, lady beetles and lacewings. Sow it from late spring to mid-August; frost kills it. Mow or cut it 7 to 10 days after it starts flowering so it does not drop seed. Two cautions from the same guide: it also attracts Japanese beetles, which feed on raspberries, strawberries, eggplant and roses, and it grows poorly in heavy soil or soil with a pH above 7.

Keep the helpers working

• Go easy on insecticides. Clemson Extension advises against broad-spectrum insecticides (such as organophosphates, carbamates, pyrethroids and neonicotinoids), because killing beneficial insects can let pests rebound. If you must treat, Penn State suggests low-residual products, used only where needed.
• Do not overfeed or overwater. UC IPM notes that excess nitrogen fertilizer and irrigation favor aphids.
• Control ants. Ants protect aphids and other honeydew-producing pests from their natural enemies, UC IPM explains.
• Tolerate a few pests. Predators arrive after their prey, so a few aphids are what bring lady beetles and hover flies in.

What to avoid

• Plants that host your crops' pests or diseases. UC IPM warns that some insectary plants also support pests, so choose flowers that do not share problems with the vegetables next to them.
• Fennel among the vegetables. It attracts beneficial insects but is listed as a poor neighbor for many crops; grow it in its own spot. See what to plant with fennel.
• Expecting a cure. UC IPM notes that insectary plants do not always increase pest control. Treat a border as one part of good garden habits, alongside healthy soil, crop rotation and checking plants often.

Frequently asked questions

What flowers attract beneficial insects?

Small, open flowers such as dill, cilantro, sweet alyssum, buckwheat, parsley and fennel attract tiny parasitic wasps and flies, and daisy-type flowers such as yarrow, cosmos, coreopsis, sunflowers and signet marigolds attract lady beetles and other larger predators. Penn State and Clemson Extension list these groups.

What is an insectary garden?

A planting of flowers grown to feed beneficial insects with nectar and pollen, so they stay in the garden and attack pests. It can be a border, a strip along a bed or clumps among the vegetables.

Where should I plant flowers for beneficial insects?

Close to the crops you want to protect. UC IPM notes the benefit decreases with distance, so plant along bed edges, at row ends or in clumps inside the garden.

What flowers attract ladybugs?

Penn State Extension says aster-family flowers such as yarrow, cosmos, coreopsis, sunflowers and signet marigolds attract lady beetles. A few aphids also help, because lady beetles follow their prey.

Do insectary plants really reduce pests?

They often help, but not always. UC IPM notes they do not always increase biological control. They work best alongside other habits, such as avoiding broad-spectrum insecticides, not overfeeding plants with nitrogen and controlling ants.