Brussels sprouts

About

A blown sprout is one that has opened into a loose leafy rosette instead of a firm button, and it is what happens when the plant has been able to move.

Brussels sprouts need the firmest ground of any vegetable. The plant is tall, top-heavy and stands through autumn gales, and every time the stem rocks in the wind the root plate is disturbed and the sprouts loosen. Firm soil, deep planting, earthing up and a stake are the four things that prevent it, and skipping any of them shows in the crop.

The other half is soil preparation done the previous autumn. Manure the bed, leave it to settle all winter, tread it firm in spring, and do not fork it again. Sprouts planted into freshly dug fluffy ground blow whatever else you do.

Get that right and they are straightforward. One planting in June gives a crop from October to February, picked a few at a time from the bottom of the stem upwards.

Frost improves them. Cold weather converts starch to sugar and sprouts picked after a hard frost are noticeably sweeter, which is why they belong on a Christmas table rather than an August one.

Modern cultivars are far less bitter than the ones people remember from the 1970s, since breeders have reduced the glucosinolate content substantially.

Appearance and character

A biennial grown as an annual, reaching 60 cm to 1 m on a single stout upright stem.

Sprouts are miniature cabbages, 2 to 4 cm across, formed in the leaf axils all the way up the stem, and they mature from the bottom upwards.

Leaves are large, blue-green and long-stalked, held on the stem above and among the sprouts, with a substantial rosette at the top.

The top rosette is edible and is a good vegetable in its own right, often called sprout tops.

A good plant carries 50 to 100 sprouts, tightly closed and firm.

Red cultivars such as ‘Red Ball’ and ‘Rubine’ produce purple-red sprouts, which are handsome and generally lower yielding.

F1 hybrid cultivars produce sprouts that mature more evenly up the stem, which suits picking the whole stem at once, and open-pollinated types mature over a longer period, which suits picking a few at a time.

Left to a second year the plant bolts, and the flower shoots are edible.

Where it is from

Bred from wild cabbage, Brassica oleracea, in the Low Countries, with records from around Brussels in the sixteenth century and probably earlier.

The name records that origin, and the crop remains particularly associated with Belgium and the Netherlands.

It reached Britain in the late eighteenth century and became a standard winter vegetable in the nineteenth.

Sprouts are the same species as cabbage, kale, broccoli, cauliflower and kohlrabi, each being a selection of a different part of the same wild plant. Sprouts are the selection for the lateral buds.

Britain grows a disproportionate quantity by European standards, and the Christmas association is a British and Irish habit rather than a general one.

Bitterness in sprouts comes from glucosinolates. Dutch breeders identified the compounds responsible in the 1990s and bred them down substantially while keeping yield, which is why sprouts taste milder now than they did a generation ago.

Sprouts are frost hardy to around -10 deg C and improve in flavour after frost, which fits them to a British winter better than almost any other vegetable.

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 leave the ground to settle all winter. This matters more for sprouts than for any other brassica.

Tread the bed firm before planting, and do not dig or fork it again.

Sow from March to April in a seedbed or in modules, 1 to 2 cm deep.

Choose the cultivar by season. Early cultivars crop from September to November, mid-season from November to January, and late from January to March. Growing two gives a longer harvest.

Transplant in May or June when the plants have five or six true leaves and are 10 to 15 cm tall.

Plant at 60 to 75 cm spacing. Sprouts need room, and crowded plants produce small loose sprouts.

Plant deeply, burying the stem to the base of the lowest leaves, and firm in hard with your heel until the plant resists a firm tug on a leaf.

Water in generously.

Net the bed with fine insect mesh from planting to harvest, which excludes cabbage whites in summer and pigeons in winter.

Top dress with a nitrogen feed in midsummer, and stop all nitrogen after August, since late soft growth produces loose sprouts and frost damage.

Earth up the stems in early autumn, drawing soil up 10 to 15 cm around each stem, which steadies the plant against wind.

Stake each plant on an exposed site, using a cane or a stout stick tied to the stem.

Remove yellowing lower leaves as the season goes on, which improves air movement and reduces whitefly.

Start picking from October, taking the lowest sprouts first when they are firm and walnut sized, and working up the stem over the following months.

Snap or cut each sprout off cleanly at the stem.

Pick the top rosette last, in late winter, and cook it as a green.

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

Through the seasons

Winter is the main harvest, and the flavour is best after frost. Pigeon protection matters most now.

Spring clears the last of the crop, picks the top rosettes, and is the sowing season.

Summer transplants and builds the plants, takes the midsummer nitrogen feed, and is the peak caterpillar period.

Autumn earths up and stakes the plants, and picking starts in October.

Care difficulty

Moderate. Sprouts are not difficult to grow and they are easy to grow badly, and the difference is almost entirely soil firmness and wind.

The failures are all versions of the same thing. Blown sprouts come from loose ground, from freshly dug soil, from insufficient firming at planting, from not earthing up, from no stake, or from too much nitrogen late in the season.

Beyond that they are a hardy undemanding crop that gives a long harvest from a single planting.

They occupy the ground from June to February, which is a real commitment on a small plot.

Watering

Water in generously at transplanting and through the first fortnight.

Water in dry spells through the summer while the plants are building their frames.

A thorough weekly soak in dry weather beats a daily sprinkle.

Established plants need little water through autumn and winter, when rainfall does the job.

Mulch after planting to conserve moisture, keeping it clear of the stems, and do not let the mulch loosen the soil surface around the plant.

Warning signs, diseases and pests

Sprouts opening into loose leafy rosettes instead of firm buttons is blowing. The causes are loose soil, wind rock, planting too shallow, not earthing up, no stake, or too much nitrogen late in the season. Prepare the ground the previous autumn, tread it firm, plant deep, firm hard, earth up and stake.

A cloud of tiny white insects rising when the plants are touched, with sticky leaves and sooty mould, is cabbage whitefly. It is largely cosmetic and washing the sprouts deals with it. Removing yellowing lower leaves reduces the population.

Leaves reduced to veins in summer with caterpillars on the undersides is cabbage whites. Net the crop from planting.

Leaves stripped in winter is pigeons. Net the crop, with the netting held clear of the foliage.

Plants leaning or blown over is wind on unstaked plants. Earth up and stake.

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.

Small sprouts on a crowded plant is spacing. Allow 60 to 75 cm.

Black rot showing as yellow V-shaped patches at the leaf edges with blackened veins is a bacterial disease. Remove affected plants and rotate.

Growing environment

Full sun.

Very firm, fertile soil limed to pH 6.5 to 7, manured the autumn before and left to settle all winter.

Very hardy, standing around -10 deg C, and the flavour improves after frost.

Allow 60 to 75 cm between plants.

It suits an allotment or a well-prepared vegetable bed, and it is a poor container crop because of the size, the wind and the length of the season.

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.

Consider the ground commitment. Sprouts occupy a bed from June to February, and on a small plot that is a significant proportion of the space.

Grow an early and a late cultivar together for a harvest running from October to March.

Feeding

Manure or compost the ground the autumn before planting and leave it to settle.

Apply a general balanced fertiliser before planting.

Top dress with a nitrogen feed in midsummer, hoeing it in and watering it.

Stop nitrogen after August. Late feeding produces soft growth and loose sprouts, and it makes the plant more vulnerable to frost.

A high-potash autumn feed is more useful than nitrogen at that point.

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

Troubleshooting

My sprouts opened into loose rosettes. Blowing, caused by the plant moving in the ground. Prepare the bed the previous autumn and let it settle, tread it firm before planting, plant deep to the lowest leaves, firm hard with your heel, earth up the stems in early autumn and stake each plant.

Why does the soil need to be so firm? The plant is tall and top-heavy and stands through autumn gales. Every time the stem rocks, the root plate is disturbed and the sprouts loosen.

When do I start picking? From October, taking the lowest sprouts first when they are firm and about walnut sized, and working up the stem over the following months.

Do they taste better after frost? Yes. Cold weather converts starch to sugar, so sprouts picked after a hard frost are sweeter. That is why they suit Christmas rather than autumn.

Should I take the top off? Stopping the plant by removing the top rosette in autumn makes the sprouts mature more evenly and is worth doing where you want to pick the whole stem at once. Otherwise leave it and eat it as a green in late winter.

There is a cloud of white flies on the plants. Cabbage whitefly, which is largely cosmetic. Wash the sprouts before cooking, and remove yellowing lower leaves.

Why are my sprouts so small? Usually crowding or a shortage of nitrogen early on. Allow 60 to 75 cm per plant and top dress in midsummer.

Can I still feed them in autumn? Not with nitrogen. Stop it after August, since late soft growth produces loose sprouts and frost damage. Potash is more useful then.

Are they less bitter than they used to be? Yes. Dutch breeders identified the compounds responsible for the bitterness in the 1990s and bred them down substantially, so modern cultivars taste milder than those grown a generation ago.