Broccoli

Growing Conditions

Broccoli forms its best heads in cool weather with temperatures between 65°F and 75°F during the day. Temperatures above 80°F during heading cause loose, open heads that flower quickly. Light frost doesn’t harm broccoli and can improve flavor. Full sun is required for compact, dense heads.

Cold climates: Start indoors 6–8 weeks before last frost. Transplant 2–4 weeks before last frost — broccoli tolerates frost well once established. For fall, start indoors in midsummer and transplant 8–10 weeks before first frost.

Warm climates: Fall and winter are the reliable seasons. Spring plantings often don’t have enough cool weather to produce quality heads before heat sets in.

Sowing & Planting

Start seeds indoors ¼ inch deep in cells or small pots. Transplant when seedlings are 4–6 weeks old with a sturdy stem. Harden off over 7–10 days before planting out. Space transplants 18 inches apart in rows 24 inches apart. Broccoli needs room — crowded plants produce smaller heads.

Care & Maintenance

Water consistently — 1–1.5 inches per week. Irregular moisture causes hollow stems and poor head development. Side-dress with a balanced fertilizer or compost when plants are 6 inches tall. Avoid excess nitrogen close to heading time — it promotes leaf growth over head development.

Common Problems

Cabbage worms (imported cabbageworm and cabbage looper) are the primary pest. Check the undersides of leaves for eggs and small caterpillars. Bacillus thuringiensis (Bt) is effective and safe for beneficial insects. Row cover prevents egg-laying. Aphids cluster on stems and under leaves — knock off with water or treat with insecticidal soap. Clubroot is a soilborne disease that causes swollen, distorted roots. Prevent through 3-year rotation and maintaining soil pH above 7.0.

Harvest

Cut the main head when it’s fully formed but before any yellow flowers open. A tight, deep green head with compact buds is ready. Cut at a 45-degree angle 5–6 inches below the head to encourage side shoot development. Side shoots will continue producing for 4–6 weeks — harvest them regularly at 3–4 inches to maintain production.

Varieties

Calabrese types (the standard supermarket broccoli) produce large central heads followed by abundant side shoots. These are the best choice for home gardens focused on extended harvest. Sprouting broccoli varieties skip the large central head entirely and produce only side shoots over a longer season. Romanesco is technically a broccoli-cauliflower cross with a striking spiral head — grow it like broccoli.