Gardening glossary
Companion planting
Companion planting is gardening folklore meeting working biology. Some pairings are backed by solid research; others are passed down because gardeners notice they work. Used together they form a productive, lower-maintenance bed.
Pairings worth using:
- **Tomatoes + basil** — basil is thought to repel thrips and whiteflies, and the two share the same water and feeding needs. - **Carrots + spring onions or chives** — the onion family masks the scent that carrot fly uses to locate carrots. - **Brassicas + dill or nasturtium** — dill attracts parasitic wasps that target cabbage caterpillars; nasturtium acts as a trap crop for aphids. - **Squash + nasturtium** — nasturtium pulls aphids away from young squash leaves. - **Beans + sweetcorn + squash** ("three sisters") — beans fix nitrogen, corn provides a trellis, squash shades the soil and suppresses weeds. - **Lettuce + tall crops (tomatoes, sunflowers)** — the tall crop shades the lettuce through summer and slows it bolting.
Combinations to avoid:
- Onions/garlic near beans and peas — alliums inhibit legume growth. - Fennel near most vegetables — fennel suppresses neighbours and is best grown in its own corner. - Brassicas near strawberries — they compete heavily and share pests.
The deeper logic behind companion planting is diversity. A bed with five species in it is harder for any one pest to wipe out than a monoculture of one. Adding flowers — calendula, alyssum, borage, phacelia — feeds beneficial insects and improves pollination of nearby fruiting crops.
Companion planting is not a substitute for healthy soil, sensible spacing, or rotation. Treat it as one tool that stacks on top of the others.