Plant profile
Broccoli
Brassica oleracea (Italica Group)
Broccoli is a cool-season brassica grown for its main head and smaller side shoots after the first harvest.
- Grows well in
- Tropical, Subtropical, Temperate, Cool / mountains, Arid / inland, Mediterranean
- Lifecycle
- Cool-season annual vegetable
- Light
- Full sun
- Mature size
- Usually about 45–90 cm tall and 45–60 cm wide, depending on variety and growing conditions.
- Spacing
- About 45–60 cm apart for full-sized plants.
- Growth habit
- Upright leafy brassica that produces a central flower head above a stout stem.
- Native range
- Cultivated group; its wild ancestor Brassica oleracea is native to the Atlantic coasts of Great Britain, France and Spain.
- Natural habitat
- Cultivated crop with no separate wild habitat; wild Brassica oleracea grows naturally on seaside cliffs.
When to plant
Tropical
April–June
Subtropical
March–June
Temperate
February–May, August–October
Cool / mountain
March–May, August–October
Arid inland
March–June
Mediterranean
February–May, August–October
Planting
Sow in trays or punnets, then transplant young seedlings. In warm districts, grow broccoli through the coolest part of the year.
Position and light
Full sun. Cooler afternoon conditions can help in warm districts.
Soil
Fertile, well-drained soil with compost. Dig in aged manure or compost several weeks before planting, and lime acidic soil to reduce the risk of clubroot.
Watering
Keep moisture even through leaf growth and head formation.
Feeding
Feed during strong leaf growth with a complete vegetable fertiliser at the label rate. A side dressing of blood and bone or a nitrogen-rich fertiliser about four weeks after transplanting supports strong leaf growth before heads form.
Pruning
No routine pruning is needed. After the main head is cut, leave healthy stems so side shoots can form.
Harvest
Cut the main head while buds are tight, often around 12 weeks. Continue picking side shoots. Harvest promptly once buds are tight and still green, since heads left too long start to open into small yellow flowers and lose quality.
Propagation
Grow from seed. Succession sowing can extend harvests.
Common problems
Cabbage white butterfly caterpillars, aphids, clubroot, snails and heat stress are common. Netting young plants keeps butterflies off before caterpillars establish, and crop rotation over several seasons helps reduce clubroot buildup in the soil.
Worth knowing
Broccoli is a brassica bred from wild cabbage, and it cross-pollinates readily with other flowering brassicas nearby, so keep flowering brassica crops separated if saving seed. Hot weather during head formation can cause the buds to open prematurely, producing small, loose or bitter heads. Growing broccoli in the same bed as other brassicas in consecutive seasons increases the risk of clubroot and other soil-borne brassica diseases, so rotate the bed between unrelated crops each season.
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