What Plants Repel Aphids?

Aphids are among the most common and damaging garden pests — they attack nearly every vegetable and ornamental, reproduce explosively in warm weather, and spread viral diseases as they feed. Companion planting tackles aphids through two strategies: deterrence (plants whose scent or chemistry makes the area less attractive to aphids) and attraction (plants that draw aphids away from valuable crops, or that attract the predators that eat them). Both approaches are valuable and work best in combination.

Catnip — Surprisingly Effective at Deterring Aphids

Catnip (Nepeta cataria) releases nepetalactone, a compound that repels aphids as effectively as DEET repels mosquitoes in laboratory studies. Crushed catnip leaves have been shown to significantly reduce aphid colonisation on nearby plants. The challenge is that catnip is attractive to cats, which may disrupt the planting. Nepeta x faassenii (ornamental catmint) releases similar compounds with less cat attraction and is a more practical garden choice. Plant dense clumps near aphid-prone crops.

Garlic and Chives — Reliable Aromatic Deterrents

Alliums release sulphur-based volatile compounds that interfere with the chemical signals aphids use to locate host plants and signal to other aphids. Dense plantings of garlic, chives, or garlic chives interspersed throughout vegetable beds measurably reduce aphid populations on nearby plants. This is one of the most frequently replicated companion planting effects and one you can implement easily — chives are perennial and essentially maintenance-free once established.

Nasturtiums as a Sacrificial Trap Crop

Rather than repelling aphids, nasturtiums attract them — and this is their value. A dense planting of nasturtiums near your most valuable crops will draw aphids to the nasturtiums and away from the vegetables. Once the nasturtiums are heavily colonised you can remove them, shake them over a bucket of water, or simply let the ladybirds and lacewings that are drawn in by the aphid concentration clean up. Nasturtiums are particularly effective as a trap crop for black bean aphid near broad beans and brassicas.

Marigolds and Their Effect on Aphid Predators

French marigolds do not directly repel most aphid species but their flowers attract hoverflies in large numbers. Hoverfly adults feed on pollen and nectar but their larvae are voracious aphid predators — a single larva can consume hundreds of aphids during its development. By providing hoverfly nectar you increase the predator population in your garden, which reduces aphid numbers on nearby crops. This is an indirect but powerful biological control mechanism.

Fennel, Dill, and Yarrow for Predator Habitat

Allowing fennel (in an isolated position away from other vegetables), dill, and yarrow to flower provides nectar for parasitic wasps that lay their eggs inside aphids, killing them. A garden that includes flowering umbellifers and composites in its borders will have significantly more of these beneficial parasitoids than a garden with only vegetable monocultures. Even a small section of flowering herbs at the edge of the vegetable area will make a difference to the biological balance of the garden.