When to plant broccoli

Broccoli, or calabrese, is a fast crop. Raise plants indoors from March, or sow into a seedbed outdoors from April, and plant them out from April to July. Several small sowings a few weeks apart give you heads from early summer until the first frosts, instead of a glut all at once.

Very early plantings need fleece. A long cold spell after planting can make young broccoli form a tiny, premature head or run to seed. In the heat of high summer, head formation can also go wrong; heat-tolerant varieties cope better with summer plantings.

In the UK, purple and white sprouting broccoli are sown in spring as well, but stand over winter and crop from late winter into spring. In most of Germany, Austria and Switzerland winters are usually too hard for that.

Sow two seeds per module or spot, 0.4–0.8 in deep, and keep the stronger seedling. Seed trays want a bright place and at least 59°F; seedlings come up in about a week. After four to five weeks, when they stand 4–6 in tall with a few true leaves, they are ready to go out.

Plant into rich, well-limed soil with plenty of compost; a pH of 6 to 7.5 suits broccoli, and the upper end helps against clubroot. Set each plant 0.8–1.2 in deeper than it grew, up to the lowest leaves, firm it in and water well.

Allow 16–20 in between plants and 20–24 in between rows, or 20 in each way. A 120 × 80 cm raised bed holds four plants at full spacing, or six at 16 in apart.

Broccoli puts on a lot of growth in the eight to ten weeks after planting, so it needs plenty of nutrients. It is a Starkzehrer, a heavy feeder. On poor soil, work in a generous amount of compost before planting and give a nitrogen-rich organic feed once the plants are about 8 in tall.

Water young plants until they are established and whenever the soil dries out. A check in growth from drought, cold or hunger can leave you with small, early heads.

Cut the main head while the buds are still tightly closed, before any yellow flowers show. Take it with a good piece of stalk: peeled, the stalk is as good as the florets.

Once the main head is gone, many varieties send out smaller side shoots from the leaf joints. Keep cutting them before they flower and you can pick for several more weeks. Varieties bred for many small heads are especially good for this.

Broccoli doesn't keep long. It lasts a few days in the fridge; for longer, freeze the florets.

Calabrese is what supermarkets sell as broccoli: one big green head in summer or autumn, followed by side shoots. It takes about 12 weeks from sowing.

Sprouting broccoli, purple or white, is a much bigger, slower plant that crops over about eight weeks in late winter and spring. Snap the spears when they are 4–8 in long, before the flowers open. It is popular in the UK because it fills the hungry gap; whether it survives colder Central European winters is a gamble.

Three pests do most of the damage: cabbage root fly maggots, mealy cabbage aphids and caterpillars. Aphids and caterpillars can hide deep inside a head, which is no fun to find in the kitchen.

Cover the plants with insect mesh straight after planting and tuck the edges in all round. Mesh of about 1.3 mm keeps out cabbage whites and root fly; 0.8 mm also stops mealy aphids and flea beetles. Bird netting has holes far too big for insects.

Without mesh, fit a collar 3–6 in across tightly around each stem at planting to stop root fly laying eggs, check the leaf undersides every week for yellow egg clusters and caterpillars, and remove the first aphid colonies straight away. Cabbage white caterpillars feed from about May to October.

Clubroot makes the roots swell into solid clubs; plants wilt on warm days and stay small. The spores last in soil for many years, up to 20. Keep the pH around 7, raise plants in pots, bin infected roots and leave at least four years before cabbage-family crops go back in the same bed, seven or more after an outbreak. Clubroot-resistant calabrese varieties exist, such as 'Komodo' and 'Monclano'.

Broccoli is in the cabbage family (Brassicaceae) with cabbage, kale, cauliflower, kohlrabi, radishes, turnips and rocket. All of them, and mustard as a green manure, count for rotation.

Mixed-planting charts suggest all kinds of partners for broccoli, such as celery, lettuce or herbs. We found no solid research behind these pairings; they are tradition. The one sensible rule is not to crowd it among other cabbages, which share its pests.

The advice with real support: underplanting brassicas with low clover makes them harder for cabbage root fly to find, and mixed plantings in general tend to carry fewer pests than a bed of a single crop. Plan good rotation partners too: leeks, onions, courgettes or sweetcorn are good crops to grow before broccoli.