Kale companion plants: brassicas need help
Kale (*Brassica oleracea* var. *sabellica*) is among the most heavily attacked vegetables in the home garden. Imported cabbageworm (*Pieris rapae*), cabbage looper (*Trichoplusia ni*), diamondback moth (*Plutella xylostella*), and aphids -- primarily cabbage aphid (*Brevicoryne brassicae*) -- treat.
Kale (Brassica oleracea var. sabellica) is among the most heavily attacked vegetables in the home garden. Imported cabbageworm (Pieris rapae), cabbage looper (Trichoplusia ni), diamondback moth (Plutella xylostella), and aphids — primarily cabbage aphid (Brevicoryne brassicae) — treat kale as a primary host. Because kale is typically grown over a long season (spring through fall frost and sometimes beyond), the pest window is long.
Companion planting for kale works on three mechanisms: aromatic masking of glucosinolate signals, provision of nectar and habitat for parasitic insects, and trap cropping.
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The companion planting table
| Plant | Role | Friend / Foe / Neutral | Notes |
|---|---|---|---|
| Dill (Anethum graveolens) | Attracts Braconid wasps, parasitizes caterpillars | Friend | Allow to flower |
| Cilantro (Coriandrum sativum) | Attracts Aphidius wasps that parasitize aphids | Friend | Succession-sow every 3 weeks |
| Sweet alyssum (Lobularia maritima) | Syrphid fly attractor; larvae eat aphids | Friend | Row edges and paths |
| Nasturtium (Tropaeolum majus) | Aphid trap crop | Friend | Remove when infested |
| Thyme (Thymus spp.) | Aromatic confusion for cabbage moths | Friend | Low-risk; plant as row border |
| Sage (Salvia officinalis) | Aromatic deterrent for cabbage moths | Friend | Some evidence; mechanistic proof limited |
| Garlic / onion | Sulfur volatiles may deter aphids | Friend (tentative) | Low-risk addition |
| Marigold, French (Tagetes patula) | Beneficial insect habitat; nematode management | Friend | Works best at dense, bed-scale planting |
| Mint (Mentha spp.) | Strong aromatic; anecdotal evidence of deterrence | Friend (tentative) | Plant in container to prevent spreading |
| Beets | Compatible; useful space sharing in cool season | Neutral | No pest interaction documented |
| Spinach | Low, non-competitive; efficient use of space | Neutral | Harvest before kale canopy closes |
| Fennel (Foeniculum vulgare) | Strongly allelopathic to brassicas | Foe | Separate beds entirely |
| Other brassicas | Concentrates specialist brassica pest load | Foe | Rotate brassicas as a family; don't block-plant |
| Mustard (mature) | Hosts diamondback moth and cabbageworm | Foe | Young plants only as trap crop; remove before maturity |