How to Sow and Grow Broccoli: A Complete Guide

Broccoli needs patience, fertile soil and firm planting, but a protected crop can be extremely rewarding. The word broccoli covers fast summer calabrese, which makes a large central head followed by side shoots, and sprouting broccoli, which usually overwinters and crops the following spring.

Choosing the right broccoli

Choose calabrese for a crop in the same growing season and purple or white sprouting broccoli for a longer-term harvest. Check the seed packet carefully: sowing dates vary widely between cultivars. Compact calabrese suits smaller plots; sprouting types become large plants and occupy ground through winter.

When to sow broccoli

Sow calabrese from early to late spring for summer and autumn heads. Sow sprouting broccoli from mid to late spring for harvest the following year in temperate climates. In very hot regions, schedule broccoli as a cool-season crop because high temperatures cause small or loose heads.

How to sow

Sow 1–2 cm deep in modules or a sheltered seedbed. Keep at about 15–20°C until germination, then grow seedlings in bright, cooler conditions. Thin promptly. Module plants should be potted on or planted before they become root-bound; crowded, stressed seedlings may form undersized heads later.

Preparing the soil

Choose full sun and moisture-retentive, well-drained soil. Add mature compost in advance. Brassicas perform best in firm ground, so avoid freshly dug, fluffy soil immediately before planting. Where soil is acidic, apply lime only after a soil test and well before planting; do not lime simply as a routine.

Planting and spacing

Harden plants for 7–10 days. Plant deeply, up to the lowest leaves, and firm the soil around each stem. Space calabrese about 45–60 cm apart and large sprouting broccoli 60–75 cm apart, with similar spacing between rows. Water in thoroughly and stake tall plants in windy positions.

Watering and feeding

Water during dry spells, especially while heads develop. Mulch to conserve moisture and suppress weeds. Fertile soil may need only compost; on poor ground, use a balanced organic feed according to the label. Excess nitrogen creates soft growth vulnerable to pests, while severe hunger limits head size.

Protecting broccoli from pests

• Cabbage caterpillars: cover with fine insect-proof mesh before butterflies arrive and inspect leaves for eggs.

• Pigeons: use strong, well-supported netting, especially in winter.

• Flea beetles: protect seedlings with mesh and keep them growing steadily.

• Cabbage root fly: fit brassica collars snugly around stems and rotate crops.

• Slugs: protect young transplants with wildlife-safe barriers and checks.

Diseases and disorders

Clubroot causes swollen roots and wilting; improve drainage, raise transplants separately and avoid moving contaminated soil. Rotate brassicas for several years. Small premature heads, often called buttoning, can follow cold, root restriction, drought or other checks to growth. Loose heads may result from heat or late harvesting.

Harvesting broccoli

Cut calabrese while buds are tight and before yellow flowers open, taking 10–15 cm of stem. Leave the plant in place for smaller side shoots. Pick sprouting broccoli regularly from the centre outward; frequent cutting encourages further shoots. Cool harvested heads quickly and refrigerate, or blanch and freeze surplus.

After harvest

Remove roots at the end of cropping and check for clubroot. Compost only healthy material. Follow broccoli with a non-brassica crop and maintain rotation across cabbage, kale, radish and other members of the same family.