How to Grow Broccoli
Brassica oleracea var. botrytis cymosa
Sproutingis very similar to but instead of culminating in a single, terminal curd the plants produce a more branched and loose collection of flower heads, many of which are in leaf axils lower down the stem. Purple sprouting broccoli — which goes green during cooking—is most popular, but there is a lesser known white form. Both mature in the winter and are hardy in most areas, providing a useful continuity and variation of winter greens. Green sprouting broccoli is better known as calabrese and is becoming increasingly popular. It is much-liked in Italy but is not winter hardy in Britain and must be harvested in August and September. Calabrese is a superb vegetable for your freezer. There is also a perennial sprouting broccoli which will go on producing for several years.
Soil and fertilizer requirements
Overwintering purple and white forms of broccoli have the same needs as winter cauliflower. They do best after well-manured crops such as earlyand, of course, need well-drained soils. Once again there is a danger of high winds blowing plants over during the winter so it is worthwhile earthing up around the stems. Calabrese is a summer-grown brassica which must be grown rapidly if you are to get young tender shoots or ‘spears’. This means that summer/ autumn cauliflower conditions are needed. Soils must be fertile and well-drained but also moisture-retentive. Constant supplies of water and nitrogenous fertilizer are needed if the necessary strong plant framework is to be produced.
Sow the seed of purple and white sprouting forms in an outside seedbed in mid-April. Sturdy plants are required which means that themust develop at a spacing of 1.5cm (3/4in) apart—in drills 1cm (1/2in) deep and 20cm to 30cm (8in to 12in) apart. The tender calabrese requires an earlier start to plant raising. Seed can be sown in an outside seedbed during late March or early April—as described above—in very sheltered areas with light well-drained . Better results will be obtained if the plants are raised in a cold frame or under cloches. Having put the frames/cloches over the soil well in advance to warm it up, you can sow the seed in the same way as for purple and white sprouting forms, in early April. Plants of perennial broccoli are best raised in the same way as purple and white sprouting forms.
Transplanting and crop management
Winter and perennial broccoli are transplanted in June or July—the former at 75cm (30m) square and the latter at 90cm (36m) square. Purple and white sprouting forms will probably respond to a worked-in top dressing of 50g per m2 (2 oz per sq yd) of Nitro-Chalk in early spring.
Calabrese should also be planted out in June at 75cm (30in) square and grown rapidly through the summer months. It is necessary to look out for the common brassica pests such as aphids, caterpillars androot fly.
Remove sprouting side shoots when they are mature so that more will be produced further down. Snap them off as close to the main stem as possible. A number of purple/ white cultivars are available to spread the season from January until April or May. Perennial broccoli produces a large central head surrounded by half-a-dozen or so smaller axillary heads. In order to keep the perennial habit of the plant these heads must all be cut off at the end of the season before going to seed. Calabrese plants also produce a central head of terminal shoots initially but when these are cut side branches quickly develop. The increased popularity of this vegetable has led to the recent introduction of new cultivars—including a number of very uniform and high yielding F1 hybrids —which allow you to extend the season from August until October.
Pests and diseases
Sprouting broccoli are liable to be attacked by the sameas . Reduce the destructive effects of aphids as soon as they become evident with sprays of malathion. Cabbage root fly, the pest common to all members of the brassica family, is resistant to many insecticides. The only effective defence against infestation by this pest is to apply a root chemical such as triclorphon to the seedlings before trans-planting. Malathion, triclorphon and derris may also be used against caterpillars.
* indicates suitability for freezing
Purple/white Sprouting broccoli ‘Early Purple Sprouting’: February/March. ‘Late Purple Sprouting’: April. N.B.—there are White Sprouting forms of both cultivars.
Green Sprouting broccoli/Calabrese ‘Express Corona’*: F1 hybrid; heavy crop in August/ September. ‘Green Comet’*: F1 hybrid; large, early heads. ‘Italian Sprouting’: September onwards.
Perennial broccoli ‘Nine Star’: late spring. ‘Hen and chickens’: produces small white heads in May.