When to plant cauliflower

Cauliflower is grown from young plants. For the first crops, sow indoors in February or March; from April you can also sow into an outdoor seedbed under fleece, and from May under insect mesh. Plant out from April to July.

Instead of one big planting, set out a few plants every two to three weeks. Each batch ripens within about ten to fourteen days, so small, regular plantings give you heads over a long season rather than ten at once. Plants set out in July grow in the cooler autumn and are a good batch for freezing.

Cauliflower only forms its head properly after a spell of about two weeks below 68°F, around the time it has six to eight true leaves. In a heatwave at that stage, many varieties simply wait and head up later. For summer crops, choose varieties sold as heat-tolerant.

In mild parts of the UK, winter and spring cauliflowers are sown in late spring, stand over winter and are cut from winter into spring. In most of Central Europe that is too risky.

Sow one or two seeds per module or spot, 0.4–0.8 in deep, and keep only the strongest. The seeds need about a week to come up. After three to six weeks, with three or four true leaves and 4–6 in tall, the young plants are ready. Don't let them sit in their pots much longer: plants that grow too big before planting tend to form tiny heads early.

Cauliflower is the most demanding of the cabbages. It wants deep, humus-rich soil with plenty of compost and a pH of about 6.5 to 7.5; lime acid soil before planting, which also protects against clubroot. Plant only when the soil has dried out enough to work, never into wet ground.

Set the plants 0.4–0.8 in deeper than they grew, firm them in and water well. Allow 20 in between plants and 20–24 in between rows, three to four plants per square metre. A 120 × 80 cm raised bed has room for four.

The secret with cauliflower is to never let it stop growing. Any check, from dry soil, hunger or cold, can end in a small or loose head. Water regularly and thoroughly in dry weather and mulch the soil to keep it moist.

It is a Starkzehrer, a heavy feeder, and puts on a huge amount of leaf in a short season. Work in a generous amount of compost before planting. If the leaves turn pale and growth slows in otherwise healthy plants, give a nitrogen-rich organic feed.

Once the head appears, protect it from strong sun, which turns white curds yellow. Snap a few of the big outer leaves and fold them over the head, or tie them loosely together. The head is usually ready four to eight days later in summer, longer in autumn.

Start cutting when the heads are about 4 in across. Well-grown plants can reach 6–8 in, but the head must still be firm and tight. As soon as the florets start to separate, it is running to flower and gets worse by the day. When in doubt, cut it sooner.

Harvest in the cool of the morning in summer. A fresh head keeps for about a week in the fridge. For longer storage, blanch the florets and freeze them.

Besides the classic white, there are green-yellow, orange and purple cauliflowers, and Romanesco with its pointed spiral turrets. Purple heads lose their colour in boiling water, so steam them or eat them raw.

Coloured cauliflowers and Romanesco are less forgiving than white ones and do best planted from early June to mid-July, maturing in cooler weather. They take about two weeks longer.

If clubroot is already in your soil, 'Clapton' and 'Clarify' are clubroot-resistant cauliflower varieties.

Cabbage root fly is the pest that hits cauliflower hardest. Its maggots eat the roots and bore into the stem; plants wilt and die, often within days. Young plants are at risk from sowing until about four weeks after planting. Fit a collar 3–6 in across tightly around each stem at planting, or cover the bed with mesh. Later generations in late summer can also tunnel into the curd.

Caterpillars of the cabbage whites and cabbage moth, and mealy cabbage aphids, can strip a crop quickly. Check the leaf undersides weekly and remove eggs and caterpillars from about May to October.

Insect mesh laid straight after planting keeps nearly all of these out. Holes of about 1.3 mm stop cabbage whites and root fly; 0.8 mm also stops flea beetles and mealy aphids. Bury the edges and lift it only briefly. In hot spells the mesh adds warmth; you can take it off four to five weeks after planting, once root fly is less of a risk, but then watch for caterpillars.

Clubroot turns roots into solid, swollen clubs; plants wilt in warm weather and stay small. The spores survive 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 any cabbage-family crop returns, seven or more after an outbreak.

Cauliflower belongs to the cabbage family (Brassicaceae), with cabbage, broccoli, kale, kohlrabi, radishes, turnips and rocket. All of them count for rotation, and so does mustard as a green manure. Leeks, celery, tomatoes and peppers are good crops to grow before it.

Mixed-planting charts list many partners for cauliflower, such as celery, lettuce, spinach or beans. We found no good evidence that any of them help; treat them as tradition.

The idea with research behind it: a low living mulch of clover between brassicas makes them harder for cabbage root fly to find, and mixed plantings generally have fewer pests than a bed of one crop.