Broccoli

About

Two quite different crops are sold as broccoli, and confusing them is the commonest reason a sowing disappoints.

Calabrese is the one in the shops. A large tight green head on a thick stem, ready within three months of sowing, cropping from July to October, and killed by hard frost. It is an annual, it is sown in spring and eaten the same year, and it bolts in hot dry weather.

Purple sprouting broccoli is a different proposition. Sown in spring, planted in summer, it stands all winter as a large leafy plant and produces its crop of small purple spears from February to April. It occupies the ground for nearly a year and it arrives in the hungry gap when a vegetable garden has almost nothing else.

For a small plot calabrese makes more sense. For an allotment, purple sprouting is one of the best things you can grow, because nothing else fills February and March.

Both are cut-and-come-again. Take the central head first and the plant produces a succession of side shoots for several weeks afterwards, and cutting regularly is what keeps them coming.

Appearance and character

An upright brassica reaching 45 to 60 cm for calabrese and 75 to 90 cm for sprouting types.

Calabrese produces a single large dense head 10 to 20 cm across, made of tightly packed green flower buds on thick fleshy stalks, followed by smaller side shoots from the leaf axils.

Purple sprouting broccoli produces no large central head. Instead it makes many small spears 10 to 15 cm long, each a loose cluster of purple buds on a slender stem, from the top of the plant downwards.

White sprouting broccoli is the same crop with cream-white spears.

Leaves are blue-green, oval and toothed, larger and coarser on sprouting types.

Sprouting broccoli plants are substantial by autumn, up to a metre across, and they need the space.

The heads and spears open into yellow four-petalled flowers if left, at which point they are tough and past eating.

Tenderstem broccoli is a hybrid between calabrese and Chinese kale, producing long thin green spears, and it is grown like calabrese.

Where it is from

Bred from wild cabbage, Brassica oleracea, in southern Italy, where the selections for flower heads were developed.

The name comes from the Italian broccolo, meaning the flowering top of a cabbage, and calabrese refers to Calabria.

Broccoli reached England in the early eighteenth century, where it was known as Italian asparagus, and it stayed a minor crop until the twentieth century.

Calabrese became a major commercial crop only after the Second World War, driven largely by American production and freezing.

Purple sprouting broccoli is the older type in Britain and has been grown here since at least the eighteenth century as a winter and spring vegetable.

Broccoli is the same species as cabbage, kale, cauliflower, Brussels sprouts and kohlrabi, each being a selection of a different part of the same wild plant.

Sulforaphane, produced when the tissue is damaged, has been the subject of extensive research into brassicas and health, and broccoli sprouts are one of the richest sources.

How it grows

Lime the bed the autumn before if the soil is acid, aiming for pH 6.5 to 7.

Dig in well-rotted manure or compost the autumn before and let the ground settle over winter.

For calabrese, sow from March to June, in modules rather than in a seedbed, since calabrese resents root disturbance and bolts if checked.

Sow every three weeks for a succession, or sow a bolt-resistant cultivar for a later crop.

Plant out at 30 to 45 cm spacing when the plants have four or five true leaves, and do not let them get pot-bound first.

For purple sprouting broccoli, sow from April to May in a seedbed or in modules, plant out June to July at 60 cm spacing, and harvest February to April.

Tread the bed firm before planting and firm each plant in well, particularly for the tall sprouting types.

Water in generously.

Net the bed with fine insect mesh from planting to harvest, which excludes cabbage whites, pigeons and cabbage root fly together.

Water steadily. Calabrese in particular bolts if it dries out.

Top dress with a nitrogen feed six weeks after planting.

Stake sprouting broccoli in autumn and earth up the stems, since a metre-tall plant in a February gale goes over.

Top dress sprouting broccoli again in late February as the spears start.

Cut the central head of calabrese while the buds are still tight, before any yellow shows. Cut it with 10 cm of stem and the plant produces side shoots for another four to six weeks.

Cut sprouting broccoli spears when they are 10 to 15 cm long and still in tight bud. Take the topmost spear first, which triggers the side shoots, then pick every few days.

Keep picking. Both types stop producing as soon as any shoot is allowed to flower.

Rotate. Do not grow brassicas in the same ground more than one year in three or four.

Through the seasons

Winter is when sprouting broccoli stands in the ground, and the first spears appear from February in a mild year.

Spring is the sprouting broccoli harvest through to April, and the main sowing season for both types.

Summer plants out both types, harvests early calabrese from July, and is the peak caterpillar period.

Autumn harvests late calabrese, builds the sprouting plants, and is when to stake and earth them up.

Care difficulty

Moderate. Sprouting broccoli is straightforward and calabrese is the fussier of the two.

Calabrese bolts. Heat, drought, root disturbance at transplanting and any check to growth send it straight into flower with a small useless head, and module-raising plus steady watering is the answer.

Sprouting broccoli asks for space, firm ground, staking and eleven months of patience, and it repays all of it.

Both need netting from day one, and both stop cropping the moment you let a shoot flower.

Club root affects them as it does all brassicas.

Watering

Water in generously at transplanting and through the first fortnight.

Water regularly and steadily through the growing season, and calabrese in particular needs consistent moisture to avoid bolting.

Give a thorough weekly soak in dry weather rather than a daily sprinkle.

Water sprouting broccoli through dry summers while the plants are building, and it needs little through the winter.

Mulch after planting to conserve moisture, keeping it clear of the stems.

Warning signs, diseases and pests

Calabrese producing a small loose head that opens into yellow flowers is bolting, caused by heat, drought or a check at transplanting. Raise plants in modules, keep them watered, and choose bolt-resistant cultivars for late sowings.

Leaves reduced to veins with caterpillars on the undersides, or caterpillars inside the head itself, is cabbage whites. Net the crop with fine insect mesh from planting, and soak harvested heads in salted water to bring out anything hidden.

Leaves shredded in winter is pigeons on sprouting broccoli. Net it.

Tall plants leaning or blown over is wind. Stake sprouting broccoli and earth up the stems in autumn.

Swollen distorted club-shaped roots with stunted wilting plants is club root. There is no cure and the spores last up to twenty years. Lime to pH 7.2, improve drainage and raise plants in large pots first.

Grey-white mealy colonies in the growing tip is mealy cabbage aphid. Squash small colonies and cut out affected tips.

Sprouting broccoli making a big leafy plant and no spears is usually a cultivar sown too late, or too much nitrogen. Sow April to May and top dress in late winter rather than late autumn.

Spears going straight to flower is picking too infrequently. Cut every few days once the crop starts.

Growing environment

Full sun.

Firm, fertile, moisture-retentive soil limed to pH 6.5 to 7, manured the autumn before.

Calabrese is damaged by hard frost at the head and is a summer and autumn crop. Sprouting broccoli is very hardy and stands the winter.

Allow 30 to 45 cm between calabrese plants and 60 cm between sprouting plants.

It suits a vegetable bed, an allotment or a raised bed. Calabrese works in a large container and sprouting broccoli does not, because of the space and the time.

Rotate on a three or four year cycle with the other brassicas, following legumes or potatoes.

Grow the whole brassica bed under one run of netting.

Think about the ground commitment before sowing sprouting broccoli, since it occupies a bed from July to April. On a small plot calabrese gives more per square metre.

Feeding

Manure or compost the ground the autumn before planting.

Apply a general balanced fertiliser before planting.

Top dress with a high-nitrogen feed about six weeks after planting, hoeing it in and watering it.

Top dress sprouting broccoli again in late February as the spears begin, which increases the crop noticeably.

Avoid heavy nitrogen in late autumn on overwintering plants, which produces soft growth that frost damages.

Lime the ground in autumn where the pH is below 6.5, keeping lime and manure applications in different seasons.

Troubleshooting

What is the difference between calabrese and purple sprouting broccoli? Calabrese is the supermarket type, an annual sown in spring for a single large green head from July to October, killed by hard frost. Purple sprouting is a biennial sown in spring, standing all winter and producing small purple spears from February to April.

My calabrese ran straight to flower. Bolting, caused by heat, drought or root disturbance at transplanting. Raise plants in modules rather than a seedbed, keep them watered, and use bolt-resistant cultivars for late sowings.

When do I cut it? While the buds are still tight and no yellow shows. Cut the central head with 10 cm of stem, and the plant produces side shoots for another month or more.

How do I get more side shoots? Cut the central head or the topmost spear first, then pick every few days. Both types stop producing as soon as any shoot is allowed to flower.

My sprouting broccoli made a big leafy plant and no spears. Usually sown too late, or too much nitrogen. Sow in April or May, and hold the nitrogen top dressing until late February.

There were caterpillars inside the head. Cabbage whites laying in the developing head. Net the crop from planting, and soak harvested heads in salted water for half an hour.

The plants blew over in winter. Sprouting broccoli reaches a metre and catches the wind. Stake it and earth up the stems in autumn.

Is it worth the ground it takes? Sprouting broccoli occupies a bed from July to April, which is a lot on a small plot. It is worth it if you want something to pick in February and March, when nothing else is ready.

Can I grow it in a container? Calabrese yes, one plant per 30 cm pot with steady watering and feeding. Sprouting broccoli is too large and stays too long.