How to Grow Broccoli

Beetroot's deep taproot draws up calcium and trace minerals from lower soil layers, which become available to broccoli's shallower roots as organic matter breaks down. Their different canopy heights also allow light to reach both crops.

Onion's sulphur volatiles mask the mustard-oil glucosinolates that attract cabbage white butterflies and cabbage root flies to broccoli. Interplanting rows of onion every 40–50 cm disrupts the scent corridor pests follow.

Rosemary's dense camphor and borneol vapours confuse the egg-laying flight of the cabbage moth (Mamestra brassicae), reducing larval damage to broccoli heads. Position rosemary on the windward side so volatiles drift over the crop.

Sage releases thujone and camphor that repel the cabbage moth and cabbage looper by interfering with their olfactory receptors. A border of sage around the broccoli bed creates a persistent aromatic barrier.

Nasturtiums act as a trap crop, preferentially attracting black aphids (Aphis fabae) away from broccoli with their glucosinolate-rich foliage. Remove aphid-laden nasturtium plants before populations migrate back to the brassica.

Mint's menthol and pulegone volatiles repel the cabbage white butterfly and flea beetles that riddle broccoli leaves with shot-holes. Keep mint in a buried pot to prevent it from spreading and crowding the broccoli.

Thyme's thymol and carvacrol disrupt the chemical cues that cabbage worm moths use to identify host plants, cutting egg-laying rates on broccoli. It also attracts Trichogramma parasitoid wasps that prey on caterpillar eggs.

Oregano's carvacrol and rosmarinic acid emissions repel cabbage moths and simultaneously attract hoverflies whose larvae consume aphids on nearby brassica foliage. Plant oregano as a low border to maximise volatile dispersal.

Tomatoes and broccoli compete for the same soil nutrients — especially calcium — and tomatoes release allelopathic compounds from their roots and leaves that suppress brassica growth. Keep at least 90 cm between them and avoid consecutive plantings in the same bed.

Strawberries and brassicas engage in a two-way allelopathic conflict: strawberry root exudates inhibit brassica germination while glucosinolates leached from broccoli roots suppress strawberry runner development. Separate by at least 60 cm.

Fennel exudes anethole and fenchone from its roots into the surrounding soil, compounds that directly inhibit brassica root elongation and reduce uptake of phosphorus. Keep fennel at least 1 m from any brassica bed.