How to Grow Cauliflower
Brassical oleracea var. botrytis cauliflora
This very important member of the Cabbage family has cultivars which mature at different times of the year and, if a careful choice is made, it is possible for you to haveready almost all the year round. It is difficult to maintain continuity in early summer and mid-winter due to the weather conditions prevailing at those times. In commercial horticulture the cultivars which mature in summer and autumn are termed ‘cauliflowers’ while those which mature in the winter are confusingly called ‘ ’. The former types are not frost hardy and have a more tender and delicate flavour than the hardier winter types. Complete success with winter is only likely in mild coastal areas where frost damage rarely occurs. The single stem of cauliflower culminates in a large, swollen, domed flower head comprising a mass of white or creamy-white undeveloped flower buds. This structure is known as the ‘curd’ and nestles snugly within the leaves. In the case of summer and autumn cauliflower, the leaves are usually upright or spreading whereas they tend to be wrapped over winter cauliflower as protection.
While the generalrequirements for all cauliflowers are similar there are slight variations depending on whether you are growing summer/autumn or winter types. As with all brassicas you should go for an alkaline soil which has not recently grown a related crop. It may be necessary to add lime but it is much better if club root can be kept out of the garden altogether. Summer and autumn crops must be grown without any form of check, otherwise small, immature curds will form. To avoid this condition, known as ‘buttoning’, the soil must be open, fertile and able to sustain un-interrupted growth.
The previous crop should have been well-manured, since the well-rottedwill help retain water—an essential ingredient for successful cauliflower growing. The very earliest crops which are planted in March or April to provide snowy white curds in early June need very light, open soils which drain and warm up quickly in the spring. Attempts to grow this early crop on anything but ideal soils in well-favoured districts will almost certainly end in the condition known as ‘buttoning’.
Summer and autumn cauliflower also need inorganic fertilizers, particularly nitrogen, if they are to produce large, good quality curds. A suitable programme would be a base dressing of 50g per m2 (2 oz per sq yd) of a general purpose fertilizer followed by a top dressing of 25 to 50g per m2 (1 to 2 oz per sq yd) of a nitrogenous fertilizer if required. The formula for success with summer and autumn cauliflower is, therefore, to grow them rapidly in soils which are well supplied with nitrogenous fertilizer and water. Winter cauliflower are somewhat different in that they are in their final positions during the winter period. Choose soils and fertilizer programmes which discourage lush, sappy growth developing in the autumn since this kind of plant is likely to be damaged by cold weather. Good soil drainage is important, however, along with plenty of body and depth so that a strong root system can develop. This will hold the plants steady during the winter winds and storms. When the plants start to grow again in February give them a top dressing of 50g per m2 (2 oz per sq yd) of Nitro-Chalk applied carefully around the base of the plants and hoed in. They may respond to another application in March.
The earliest summer cauliflowers require very careful plant raising. Seed may be sown in a cold frame in late September and the developingeither potted into g-cm (3-½-in) pots or pricked out into the frame soil at a spacing of 4cm x 6cm (1-1/4in x 2-1/2in). The soil/ in which the cauliflowers are overwintered should be well-drained and low in nitrogen so that sturdy young plants are produced by March/April. No heating is given but the frames must be ventilated on warm, sunny days. An alternative method of raising this group of cauliflowers is to sow seed in January in seed trays which are kept in a greenhouse with a temperature of 13°C/ 55°F. The seedlings are pricked out when they are large enough to handle into other seed trays at a spacing of 5cm x 2.5cm (2-in x 1-in).
A proprietary potting compost should be used for the pricked out seedlings. The January sowing will produce plants which are ready for planting a little after those from the September sowing, but is likely to be a more successful method. Later summer and autumn cauliflowers can be raised in an outdoor seedbed. Depending on your location and soil type sow the seed from mid-March onwards in drills 1cm (1/2in) deep and 20 to 30cm (8in to 12in) apart.
Further sowings can be made until the end of May to produce plants which are transplanted in mid-late July. Winter cauliflower plants are produced by sowing seed in an outdoor seedbed in April or May as described for the late summer/autumn types. Sow the cultivars which mature latest before those which mature first. Make sure that outdoor seedbed areas have not grown brassica plants recently and that club root fungus is not present.
Transplanting and crop management
Early summer cauliflowers are planted in March or April depending on weather and location. Spacings of between 45cm x 45cm (18in x 18in) and 55cm x 55cm (2iin x 2iin) are best. Planting too early into cold soil will cause checking and induce ‘buttoning’. Hoeing will be necessary to keep downand growth must be maintained with top dressings of nitrogen and regular waterings. Cabbage root fly larvae may attack the plants in late May as they approach readiness for cutting and you should water on a protectant chemical beforehand.
Summer/autumn cauliflowers are probably the easiest group to grow and your plants should be ready for planting about 8 to 10 weeks after sowing. The mature plants are larger than early summer types so wider spacings—up to 60cm x 60cm (24m x 24m) are used. Continuous, unchecked growth is important if you are to get top quality curds. Protection againstroot fly is likely to be necessary both in the seedbed and in the final position. Winter cauliflowers which are planted in July produce the largest plants of all and must, therefore, be spaced 75cm x 75cm (30in x 30in) and 90cm x 90cm (36m x 36m). Short, sturdy plants are essential, so thin the plants out in the seedbed if they come up too close together. A spacing of 1.5cm (1in) between seedlings in the seedbed row will ensure sturdy development. When the rate of growth slows down during the autumn months, guard against weeds.
If you live in a windy area earth up the soil around the base of the stems to prevent the plants being damaged by rocking. After topdressing in the spring the fertilizer should be worked in with a hoe to encourage rapid uptake by the plants.
Cauliflowers should be cut early in the day before the curds become over-heated. Inspect the plants regularly as they approach maturity to make sure that curds are cut as soon as they are ready. Some cultivars have leaves which curl over the tender curd and protect it from the sun’s rays. Most have upright leaves, however, and in this case break a leaf over the young curd to prevent it yellowing. Curd quality rapidly deteriorates in warm weather so regular cutting is essential.
Pests and diseases
Many of thewhich attack Brussels sprouts can also be a problem on cauliflowers—namely aphids, whitefly, cabbage root fly, flea beetles, caterpillars, birds and club root. There are no other common pests to worry you, but mention must be made of a few additional diseases and disorders. All cauliflowers are liable to develop symptoms of ‘whiptail’—a condition caused by deficiency of the micro-nutrient molybdenum. In severe cases the area of leaf blade is so reduced that the leaves become strap-like in appearance. Often the real reason for this condition is that acidity in the soil prevents the plants absorbing molybdenum. Water the plants with a molybdate solution before planting if your soil is likely to induce ‘whiptail’.
There is always a chance of frost damage on late autumn and winter crops. In the case of frost it is more likely that a secondary infection, such as grey mould (botrytis), will invade the damaged tissues and be more obvious. Cauliflower seedlings are particularly prone to downy mildew infection. Be especially vigilant with early summer types which are raised from an autumn sowing. The upper surfaces of the young leaves show yellow patches while white fungal growth can be seen on the undersides.
Damping off of the seedlings is caused by a number of soil-borne fungi while wire-stem, which causes a brown, corky constriction of the young stem at ground level, is also a soil-borne disease.
Curd peculiarities and deformities are not usually caused by disease organisms but are often a reaction to weather conditions or the absence of micro-nutrients. Brown spots on the curds can be caused by boron deficiency or by very dry growing conditions. Projections from the surface of the curd giving an uneven appearance—a condition known as ‘riciness’—are often caused by very warm weather while the curd is developing. Wide fluctuations in temperature may cause small leaves to appear in the curds when they are referred to as ‘bracted’.
All the following may be frozen.
Early Summer cauliflowers: ‘Alpha’: large, early pure white heads. ‘Snow King’: F1 hybrid; very fast growing. ‘Snowball’: reliable heads until the end of June.
Summer/Autumn cauliflower ‘All the Year Round’: aptly named, general purpose. ‘South Pacific’: good heads in early autumn. ‘Brisbane’: protected heads mature in October/November. ‘Beacon’: high quality heads in September.
Winter cauliflower: ‘Early White’: heads in January/February. ‘Snow White’: usually ready in March/April. ‘English Winter Leamington’: reliable heads in April. ‘Late Enterprise’: heads at the end of May.