Few crops repay a little planning as generously as broccoli. A single spring sowing of calabrese gives a firm green head in summer and then weeks of side shoots; a sowing of purple sprouting broccoli made at the same time stands through the winter and crops in February and March, when almost nothing else in the garden is ready. Both are forms of Brassica oleracea var. italica, and both are easy from seed — provided you understand the one thing broccoli will not forgive: a check to growth. Here is how to grow broccoli from seed, from choosing between calabrese and sprouting types to sowing, planting out, protecting and harvesting.
- Sow Calabrese February (under glass)–July · sprouting broccoli February–May
- Germination 10–20 °C · 5–10 days · 1–1.5 cm deep in modules
- Spacing Calabrese 30–40 cm · sprouting broccoli 60 cm · firm, fertile, limed soil
- Harvest Calabrese June–November · purple sprouting February–April (or summer for Summer Purple)
Calabrese or sprouting broccoli: what is the difference?
What most of us buy in the supermarket as "broccoli" is calabrese: a fast annual that forms one large, domed green head, followed by smaller side shoots once that head is cut. It is sown in spring and summer and harvested 12–16 weeks later, from June into autumn. Sprouting broccoli — in purple, green or white — forms no big central head. Instead the plant grows into a large, branching bush that produces dozens of slim, tender spears over several weeks. Traditional purple sprouting broccoli is a slow, hardy crop: sown in spring, it grows all summer, sits through the winter and crops in late winter and early spring, filling the "hungry gap" before the new season's vegetables arrive.
Botanically, both belong to the same species as cabbage, kale, Brussels sprouts and cauliflower. That matters in practice: they share the same pests, the same soil preferences and the same place in a crop rotation, so everything you already know about growing brassicas applies here.
Broccoli varieties to grow from seed
Our broccoli seeds cover both groups, so you can plan a harvest across most of the year:
- Calabrese for summer and autumn heads — Belstar F1 (also available as organic broccoli seed) is a dependable all-rounder with a good crop of side shoots after the main head. Marathon F1 is a later variety that holds its head well into cool autumn weather. Calabrese Natalino, an Italian heritage calabrese, is traditionally grown for a late harvest and is offered in conventional and organic seed.
- Purple and green sprouting — Purple Sprouting and Summer Purple give the classic tender purple spears; Summer Purple has been selected to crop in its first summer and autumn rather than waiting for spring. Montebello F1 is a green sprouting broccoli for spring sowing.
- Something different — Spigariello is an Italian leaf broccoli grown for its loose, slightly sweet leaves and small florets rather than a head; pick it like kale.
And if you want broccoli this week rather than next summer, broccoli sprouting seeds grown in a jar on the kitchen worktop are ready in four to six days — see our sprouting seeds and the guide to growing microgreens and sprouts. It is one of the few things worth sowing in the dark months; our guide to what to sow in December lists the others.
When to sow broccoli seeds
For the earliest calabrese, sow under glass in late February or March at 10–20 °C and plant out in April or May once the seedlings are hardened off. From April to early July you can sow successionally every three to four weeks for a run of heads from early summer to November; late sowings of a cold-tolerant variety such as Marathon F1 give the autumn crop. Purple sprouting broccoli is sown from March to May — April is ideal — and planted out in June or July to grow on through the summer. Check each packet: the sowing months on our product pages follow the variety, and the vegetable sowing calendar puts them side by side with everything else.
How to grow broccoli from seed, step by step
- Sow in modules, not a seedbed Calabrese in particular resents root disturbance. Sow two seeds per module or small pot, 1–1.5 cm deep, in seed compost, and thin to the strongest seedling. Germination takes 5–10 days at 10–20 °C; no extra heat is needed. More on technique in how to germinate seeds.
- Grow cool and bright Once up, keep seedlings in good light at 12–16 °C. Warm, dim windowsills give long, weak stems — the classic leggy seedling problem.
- Prepare a firm, fertile bed Choose a sunny spot that did not grow brassicas in the last two to three years. Dig in well-rotted compost in autumn or winter, lime acid soil to around pH 6.5–7.5 (this also discourages clubroot), and tread the soil firm before planting. Loose, fluffy soil lets the plants rock and gives smaller heads. See how to prepare your soil.
- Harden off and plant out young Plant out after hardening off, at four to six true leaves and four to six weeks old. Older, pot-bound calabrese often "buttons" — forms a tiny premature head and stops. Plant slightly deeper than in the module and firm in well.
- Space for the crop you want Calabrese 30–40 cm apart in rows 45–60 cm apart (closer spacing gives more, smaller heads); sprouting broccoli 60 cm each way, because the plants become large bushes.
- Net immediately Cover the bed with fine insect mesh or butterfly netting on hoops straight after planting, to stop cabbage white butterflies, cabbage root fly and pigeons. Our guide to common garden pests covers the alternatives.
- Water steadily and stake the winter crop Never let calabrese dry out — drought is the commonest trigger for bolting and small heads. Mulch to hold moisture and give a nitrogen-rich feed once a month in summer (feeding plants). In autumn, earth up and stake purple sprouting broccoli so winter gales cannot rock the roots loose.
Calabrese vs purple sprouting broccoli at a glance
Calabrese
Fast, one large head plus side shoots — the summer and autumn crop.
- Sow February (under glass) to July
- Ready 12–16 weeks after sowing
- 30–40 cm apart; sensitive to drought and transplanting checks
- Try Belstar F1, Marathon F1 or Calabrese Natalino
Sprouting broccoli
Large, hardy bushes that crop over weeks — the late-winter treat.
- Sow March to May, plant out June–July
- Overwintering types crop February–April
- 60 cm apart; stake against winter wind
- Try Purple Sprouting, Summer Purple or Montebello F1
Harvesting broccoli
Cut a calabrese head while the buds are still tight and dark green, before any yellow petals show. Take it with 10–15 cm of stem, using a sloping cut so rain runs off the stump. Leave the plant in the ground: within two or three weeks it produces a second crop of side shoots, smaller but just as good, and with regular picking it can keep going for a month or more.
Purple sprouting broccoli is picked like a cut-and-come-again crop. Snap or cut the spears when they are 10–15 cm long and the flower buds are still closed, starting with the central shoot. The more you pick, the more the plant produces — leaving spears to flower signals the plant to stop. Broccoli keeps only a few days in the fridge, so freeze any surplus: blanch florets for two to three minutes, cool in iced water and freeze flat on a tray, as described in how to freeze vegetables.
Common mistakes
- Planting out old, pot-bound seedlings. Calabrese held too long in modules buttons instead of forming a proper head. Plant out at four to six weeks.
- Letting the soil dry out. A dry spell in summer makes calabrese bolt into flower. Water deeply once or twice a week and mulch.
- Skipping the netting. One week of cabbage white caterpillars in August can strip a bed; pigeons do the same to sprouting broccoli in winter.
- Loose or acid soil. Brassicas like firm ground and a neutral to slightly alkaline pH. Tread the bed before planting and lime acid soil.
- Harvesting too late. Once yellow flowers open, the head turns tough and bitter. Check plants every couple of days in warm weather.
- Sowing sprouting broccoli too late. An overwintering crop needs a full summer to build a big frame; plants sown in July rarely produce much.
Frequently asked questions
How long does broccoli take to grow from seed?
Calabrese is ready about 12–16 weeks after sowing. Overwintering purple sprouting broccoli takes much longer — sown in April, it crops the following February to April, so up to ten months.
Why is my broccoli flowering before it forms a head?
That is bolting, usually caused by stress: dry soil, a cold snap after planting out, or seedlings that were pot-bound. Plant out young, keep the soil evenly moist and sow summer crops in succession rather than all at once.
Does broccoli grow back after you cut it?
Yes. Most calabrese produces a flush of side shoots after the main head is cut, and sprouting broccoli is designed to be picked again and again for several weeks.
Can I grow broccoli in a container?
Calabrese grows well in a large pot of at least 30 litres, one plant per pot, if you water it daily in summer. Sprouting broccoli gets too big for most containers; for small spaces, broccoli sprouts and microgreens are the easier route.
Broccoli rewards a firm bed, steady water and a net over the top — and with one calabrese and one sprouting variety in the plan, you can be cutting fresh spears for much of the year. Explore the wider brassica family in our Brassica oleracea seeds and leafy brassicas, browse all vegetable seeds or the whole seed shop, and find every growing guide in one place on our guides page.
