How to grow broccoli
Overview
Broccoli is a cool-season brassica grown for its edible flower heads, stalks, and leaves. It thrives in mild weather and requires consistent moisture and full sun for best yield. The key to perfect broccoli is harvesting the head while the buds are still tight and before any yellow petals appear.
Varieties
- Green Sprouting Calabrese — Standard large-headed variety, reliable in Australian conditions.
- De Cicco — Italian heirloom producing many small side shoots after the main head.
- Romanesco — Vibrant green fractal heads with nutty flavour, a striking garden feature.
- Waltham 29 — Cold-tolerant variety ideal for cool and mountain regions.
Soil Preparation
Broccoli prefers a pH between 6.0 and 7.0, in fertile, well-drained soil rich in organic matter. Before planting, dig in plenty of well-rotted compost or aged manure. In heavy clay soils, raise beds or add gypsum to improve drainage.
Growing Guide
Plant broccoli in full sun with well-drained, fertile soil. Space transplants 30–50cm apart in rows 60cm apart. Direct sow or start in seed trays; transplant when seedlings have 4–6 true leaves. Keep soil consistently moist and mulch to cool roots. For a continuous harvest, stagger plantings every 2–3 weeks during the growing season.
Sowing
Sow seeds 1–2cm deep, 30cm apart if direct sowing, or in punnets and transplant when 4–6 true leaves appear. Seeds germinate in 5–10 days. Broccoli transplants better than many brassicas, but avoid disturbing roots. Harden off seedlings before planting out.
Care
Feed every 3–4 weeks with a balanced nitrogen-rich fertiliser or liquid seaweed. Side-dress with compost when plants are half grown. Remove yellowing lower leaves to improve airflow and reduce disease. Maintain consistent watering to prevent stress and head splitting.
Companion Planting
Good companions include celery, dill, onion, garlic, and potatoes. Avoid planting near strawberries, tomatoes, or other brassicas to reduce pest and disease pressure. Dill attracts beneficial insects that prey on cabbage worms.
Common Pests & Risks
Cabbage white butterfly caterpillars are the most common pest; protect plants with fine netting or floating row covers. Aphids and diamondback moth also attack broccoli; spray with neem oil or insecticidal soap as needed. Slugs and snails can damage young plants; use barriers or iron-based baits.
Harvesting
Cut the main head when it is tight, firm, and 10–20cm across, before individual flowers begin to open. After the main head is harvested, side shoots will develop and can be harvested regularly for weeks. Use a sharp knife to cut the stem at an angle to prevent water pooling.
In the Kitchen
Harvest as soon as possible for sweetness; heads can be stored in the fridge in a plastic bag for up to a week. Broccoli is delicious steamed, stir-fried, roasted, or eaten raw in salads. Blanch and freeze surplus for later use.
Troubleshooting
Yellowing leaves: nitrogen deficiency or poor drainage — side-dress with blood and bone and improve soil. Brown, corky spots on stems: boron deficiency — apply a trace element mix with boron. Loose, button-sized heads: heat stress or inconsistent watering — mulch and water deeply. Hollow stems: rapid growth from excess nitrogen — reduce fertiliser frequency. Caterpillar holes: cabbage white butterfly — use fine netting from day one.