How to Grow Cabbage

Beetroot's taproot mines potassium and calcium from deep subsoil and returns them to the upper horizon as its leaves decompose, feeding the shallow fibrous roots of neighbouring cabbage. The pairing works well in rows 30 cm apart.

Onion's sulphur volatiles mask the glucosinolate odours that guide cabbage white butterfly, cabbage root fly, and aphids to their host. A border row of onions on each side of a cabbage bed creates an effective olfactory barrier.

Rosemary's high-borneol and camphor vapours create a scent screen that the cabbage moth cannot navigate through, preventing females from landing to oviposit. Plant rosemary as a permanent hedge on the prevailing wind side.

Sage's monoterpenes — particularly alpha-thujone — interfere with the sensory apparatus of the cabbage white butterfly, reducing oviposition on outer leaves. A few sage plants interspersed every 50 cm through the bed are sufficient.

Nasturtiums are a classic trap crop for black bean aphids and cabbage aphids, drawing them away from the cabbage head with irresistible glucosinolate signals. Check nasturtiums weekly and remove heavily colonised plants before populations explode.

Chard and cabbage have complementary root architectures — chard's fibrous lateral roots feed at the same depth as cabbage but in the gaps between plants, making efficient use of soil volume without head-to-head competition.

Spinach thrives in the dappled shade cast by maturing cabbage plants, using light that would otherwise be wasted while its leaf litter conserves moisture at the base of the cabbage stem. Sow spinach two weeks after transplanting cabbage.

Mint's menthol volatiles repel both the cabbage white butterfly and flea beetles, which riddle young cabbage leaves with shot-holes. Confine mint in a pot sunk to the rim to prevent invasive spreading through the bed.

Thyme's thymol disrupts the host-finding behaviour of the cabbage root fly by masking the CO₂ and glucosinolate plumes that attract egg-laying females to the soil surface around cabbage stems. Plant thyme as a dense ground-cover ring around each plant.

Oregano's carvacrol repels the cabbage moth and also draws in predatory ground beetles that hunt cabbage root fly larvae in the soil. A low border of oregano around the bed serves both as volatile barrier and beetle habitat.

Celery releases phthalides and volatile terpenes that repel cabbage white butterflies by disrupting their ability to identify the glucosinolate odour profile of their host. Alternate rows of celery and cabbage for maximum coverage.

Tomato foliage releases solanine-related alkaloids that inhibit brassica germination and slow cabbage head formation when grown in close proximity. Both also compete intensely for calcium, increasing the risk of tip-burn in cabbage. Keep at least 90 cm between them.

Strawberry root exudates contain phenolic acids that suppress the germination and establishment of brassica seedlings, while cabbage's glucosinolate leachate damages strawberry feeder roots. The antagonism runs in both directions; keep them in separate beds.

Fennel's anethole and fenchone root exudates are strongly allelopathic to brassicas, stunting root development and reducing nutrient uptake even at distances up to 1 m. Fennel should be isolated to its own dedicated bed away from all brassica family members.