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Broccoli

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Introduction

Broccoli has had a resurgence in popularity - for its high vitamin content and anti-cancer agents. It is a fast-growing and easy-to-grow crop, producing bluish-green heads that are harvested in the summer or autumn, depending on the time it is sown. The sprouting types – white or purple sprouting - are hardy and overwintered for harvest in spring, filling the gap between sprouts and spring cabbage.

Sow

Seeds are generally sown between March and June. Sow two seeds per cell of cell trays in a greenhouse or similar environment until April and outdoors from April. Thin to one plant as soon as the seedlings can be handled.

Give liquid fertiliser every week. When rootball is well bound together plant out into any fertile garden soil in full sun or very light shade.

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

Allow 30cm (12in) between plants and 45cm (18in) between rows. Closer spacing will reduce the number of side shoots formed.

Before planting add 150g per square metre of general purpose fertiliser such as Growmore, or, if manure or other rotted organic matter has been dug in use half amount of fertiliser.

From April, seeds can be sown in the open where the plants are to grow; sow three seeds, 2cm (¾in) deep, every 30cms (12in) along the row. When seedlings are large enough to be handled, thin out each ‘station’ leaving one healthy seedling behind.

Cover seedlings and seed beds with fleece to exclude cabbage root fly, removing fleece in May when risk of damage less.

Control slugs and snails as they will quickly devour seedlings.

Grow

Broccoli prefers fertile, well-drained, moisture-retentive soil.

When the young broccoli plants are 10-15cm (4-6in) high transplant indoor grown plants to their growing positions, leaving 45cm (18in) between them. Before lifting the plants, water them well and water well again after transplanting.

Thin directly-sown broccoli to 30cm (1ft) apart.

Water every 10-14 days in dry periods. Add high nitrogen fertiliser, such as sulphate of ammonia, at 35g per square metre when plants about 20cm tall.

Birds can be a problem, so net the plants when the heads are being produced.

Harvest

Cut when the flower shoots (spears) are well formed but before the individual flowers begin to open. Cut the central spear first. This is followed by a series of sideshoots, which can be picked regularly over four to six weeks.

Varieties

‘Fiesta’ AGM: Very reliable large tight heads followed by side-shoots, high yielding variety for all periods.

‘Kabuki’ AGM: Compact plants suited to small garden, especially good for autumn cropping

‘Tenderstem’: Not a heading cultivar, matures five weeks after planting. Each plant carries small crops of young spears that taste like asparagus.

Problems

Birds: Some birds, especially pigeons, will strip the leaves from broccoli, affecting the plants vigour and yield. They will also pull up seedlings.

Remedy: Scarecrows and other devices for frightening birds may work for a while, but the best way of protecting crops is to cover with fine netting, such as Enviromesh. This will also help to protect plants from caterpillars.

Read more information on birds

Caterpillars: A number of caterpillars will feed on cabbages, 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. You can spray with pyrethrum, deltamethrin or lambda-cyhalothrin. Insect-proof mesh or fine netting (5-7mm mesh) can prevent egg-laying.

Read more information on caterpillars

Club root: This is a fungal disease causing stunted growth, purplish foliage and wilting in hot weather. The root system also becomes swollen and distorted. It is worse on acidic soils and in warm, wet weather.

Remedy: If you have acidic soil you should apply lime before you plant. Test soil acidity using a pH meter which you can buy from DIY stores, or garden centres. If the pH of your soil is less than pH6, it is acidic. Once you see the symptoms of club root, there is very little you can do.

Read more information on club root

Cabbage root fly: Adult cabbage root flies resemble house flies. Their larvae are white maggots that feed on the roots and can kill seedling and recently transplanted brassicas

Remedy: Protect seed beds and young plants with fleece or insect proof mesh. Remove these when plants 15-25cm (6in-10in) tall, and place a felt collar at the base of each plant to prevent eggs being laid.

Read more information on cabbage root fly

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Sow
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Do Now

  • Sow seeds indoors
  • Once sprouted, thin to one seedling per ‘station’
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