Broccoli

Broccoli is popular for its high vitamin content and anti-cancer agents. It’s a fast and easy-to-grow crop, producing bluish-green heads for harvesting in summer or autumn. Sprouting broccoli – white or purple – is hardy and overwinters outdoors for harvesting in spring, filling the gap between Brussels sprouts and spring cabbages.

Jobs to do now

  • Water in dry spells and control weeds by hoeing
  • Harvest the first broccoli heads
  • Apply a liquid feed
  • Cover with mesh to protect from cabbage white butterflies and birds
  • Plants raised indoors can be planted out once large enough to handle

Month by month

Sow

Sow indoors

Seeds are generally sown between March and June. Until April, sow in modular trays, two seeds per module, in a greenhouse or indoors, then from April sow outdoors.

After germination, thin out the seedlings, removing the smaller or weaker one to leave one per module.

Apply a general purpose liquid feed every week.

When the young plants are 10–15cm (4–6in) tall with a good rootball, plant them outside into fertile soil in sun or very light shade.

Prepare the ground by adding a high potassium general fertiliser, such as Vitax Q4, at a rate of three handfuls per square metre/yard. Alternatively, if well-rotted manure or garden compost has been dug in, use half the amount of fertiliser.

Space plants 30cm (1ft) apart, with 45cm (18in) between rows. Closer spacing will reduce the number of sideshoots, leading to a smaller crop.

Sow outdoors

From April, seeds can be sown outdoors where the plants are to grow. Sow three seeds, 2cm (¾in) deep, every 30cm (1ft) along the row.

Control slugs and snails as they will quickly devour seedlings.

When the seedlings are large enough to be handled, thin out each ‘station’, leaving one healthy seedling every 30cm (1ft).

Grow

Grow

Broccoli grows best in fertile, well-drained, moisture-retentive soil, in full sun or very light shade.

Cover seed beds and newly transplanted indoor-raised plants with fleece to exclude cabbage root fly. You can remove it in May, when the risk of damage is reduced.

Water broccoli every 10–14 days in dry weather.

When plants about 20cm (8in) tall, add a high nitrogen fertiliser, such as sulphate of ammonia, at 35g (1oz) per square metre/yard.,

Birds can be a problem, so net the plants when heads are starting to form.

Better heads are produced in cooler summers, as hot weather can encourage plants to go to seed prematurely – some cultivars resist this tendency better than others (see Recommended Varieties below).

Harvesting

Harvesting

Regular sowings of broccoli can provide crops from late winter through to autumn, depending on sowing time and variety. Plants generally take two or three months to start cropping, then provide pickings for about a month.

Broccoli is ready to harvest when the heads or spears are well formed but still in bud, before individual flowers begin to open.

Cut the central spear first. This is followed by a series of smaller spears on the sideshoots, which can be picked regularly over four to six weeks.

Recommended Varieties

Common problems

Birds
Birds

Birds, especially pigeons, can cause an array of problems including eating seedlings, buds, leaves, fruit and vegetables.

Remedy

Protect the plants from birds by covering them with netting or fleece. Scarecrows and bird-scaring mechanisms work for a while, but the most reliable method of protection is to cover plants with horticultural fleece or mesh.

Caterpillars
Caterpillars

A number of caterpillars will feed on brassicas, but the most common are those of cabbage white butterflies. You will usually see the caterpillars, if not, you will see the holes they make in the leaves. They will also bore into the heart of cabbages.

Remedy

In mild attacks, or if you have only a few plants, you may be able to pick the caterpillars off. Insect-proof mesh or fine netting (5-7mm mesh) can prevent egg-laying.

Club root
Club root

Roots become swollen and distorted, and leaves become pale and yellow and wilt easily. Plants may die.

Remedy

Improve drainage and add lime to make soil more alkaline. Do not grow in affected soil.

Cabbage root fly
Cabbage root fly

White larvae approximately 5cm (2in) long, feed on the roots just below the soil surface, stunting growth and causing plants to wilt and die.

Remedy

Grow under insect-proof mesh or horticultural fleece. Seedlings are most vulnerable.

Recipes

This recipe for purple sprouting broccoli with anchovy dressing is perfect to serve as a main meal or as a side vegetable dish, and can be eaten all year round.

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.