A-Z of growing cauliflower

Cauliflower is a flower vegetable that belongs to the brassica family together with cabbage, broccoli, kale, Chinese cabbage and Brussel sprouts.

The only difference is that while cabbage forms a head, cauliflower forms white curds. The edible part is the white flower buds and stems.

The crop has low demand in the domestic market and is grown mainly for the high-end market, according to the Horticulture Validated Report (2014).

Cauliflower is mainly produced in Kiambu, which accounts for 89 per production mainly due to the county’s close proximity to Nairobi, the main market. Other producing counties include Taita Taveta and Kakamega.

The crop has numerous health benefits, including it helps to reduce cancer risk, fights inflammation, decreases the risk of heart diseases and brain disorders, improves digestion, is a good detoxifier, aids in weight loss, helps balance hormones and maintains good eye health.

It is rich in vitamins C and K and other minerals such as calcium, magnesium, phosphorous, potassium, zinc, sodium and iron.

Environmental requirements

For best growth and quality cauliflower, moderately uniform cool temperatures are needed. Too much heat can prevent curd formation.

While still vegetative, plants have some frost resistance, but freezing temperatures can cause considerable damage once buds and inflorescence have formed.

Exposure of cauliflower to temperatures below 10°C after field planting leads to premature flowering and the formation of smaller heads called ‘buttons’.

The optimum temperature range for curd formation is 13.9-20°C. Above 20°C, the quality is reduced. Above 25°C, curds may not form at all.

Cauliflower curd formation is more sensitive to temperature extremes, which may cause several different types of market defects.

As temperatures near 0°C, freezing injury to shoot apices may result in no curd development. High temperatures may cause the plants to regress into vegetative growth and cause small leaves to develop in the curd.

The crop needs well-drained soils, friable and with high water-holding capacity. The best soil pH is 5.5 – 6.5. The crop requires constant water supply for good growth and yields. Hence, where rainfall is inadequate, irrigation water should be available.

Cauliflower has a relatively high requirement for molybdenum, whose deficiency occurs in acidic soils with pH less than 5.5. Molybdenum deficiencies can be corrected by liming, foliar fertiliser applications or seed treatment.

Crop establishment

Cauliflower is propagated by seed, which are sown in the nursery bed and later transplanted after three to four weeks to rows 60-75cm apart and 45-60cm within the rows.

Wider spacing (75x60cm) is usually adopted for late-maturing cultivars and closer spacing (60x 45cm) for early-maturing cultivars.

Before transplanting, the nursery bed should be thoroughly watered three to four hours in advance to minimise damage during lifting of seedlings.

Preferable, remove seedlings separately, never pull as this may damage feeding roots.

Fertiliser application

Cauliflower is a heavy feeder of nitrogen and potassium. Organic matter, phosphorous and potassium fertilisers should be applied before transplanting.

Top dressing using nitrogenous fertilisers is done four weeks after transplanting and three weeks thereafter. Rates are 5-10g/plant (185-370 kg/ha) of CAN and 200 kg/ha DSP.

Irrigation

Cauliflower has a shallow root system and, therefore, when the plants are growing, they will require constant availability of moisture.

Adequate moisture promotes production of large heads. Lack of adequate moisture may lead to tough, fibrous stalks and tip-burn of broccoli.

Weed control

It is shallow-rooted and care should be taken not to damage roots in the field as this would encourage entry of fungi and bacteria.

Clean weed control methods should be practised to avoid competition for water and nutrients. Mulching may also be carried out for weed control and moisture conservation.

In cauliflower, as the white curds appear, they should be protected from full sunlight which tends to turn them to creamy yellow, reducing market quality.

Early-maturing cultivars must be protected from sun injury by tying the long outside leaves loosely over the forming heads, a procedure referred to as blanching.

Late-maturing cultivars usually have enough foliage and are self-blanched by the in curving of the inner leaves.

Harvesting

It is harvested by hand as soon as the curds have attained market size but before they become discoloured, loose and ricey. Marketable heads should be cut with three to four whorls of leaves.

These should be trimmed long enough to leave a circle of petioles to protect the head.

PESTS AND DISEASES

The pests and diseases which attack cabbage, broccoli and kale are the same ones that attack cauliflower.

Pests

Aphids

They suck sap, causing curling of leaves and transmit viruses. Control: systemic insecticides; biological – lady bird beetle; cultural – intercropping, mulching using coloured mulch.

Diamond back moth

The caterpillar causes damage to cauliflower. It is the most important pest of brassicas worldwide. It feeds on leaf lamina from the underside causing windowing effect.

Control: Use of chemicals; biological – Bacillus thuringiensis; cultural – intercropping with strong smelling crops like garlic, parsley.

Cut worm

Larvae feed on stem base cutting it off. It is more serious at transplanting.

Control: Chemical – dusting around stem bases of transplants, using chemical baits (sugar in water + poison); cultural – unearth larvae and kill them.

Diseases
i) Black rot

Caused by Xanthomonas campestris pv campestris.

Characterised by yellow angular spots that progress inward from the leaf margin. Leaf veins become dark brown to black and heads may be deformed.

Control: Crop rotation with crops that are not related to broccoli. Use of clean seeds for planting, use of clean transplants, use of resistant varieties and practising good sanitation.

ii) Alternaria leaf spot

Caused by Alternaria brassicae. Symptoms include yellow, concentric spots on foliage. Infected broccoli seedlings may be stunted or killed.

Control: Crop rotation and use of clean seed.

iii) Downy mildew

Caused by Peronospora parasitica. The symptoms are yellow spots on the upper surface with bluish white fungal growth on the lower surface of leaves.

Control: Crop rotation, practise good sanitation, and weed management.

iv) Damping off

Caused by Rhizoctonia solani or Phytium spp

It’s a fungal disease and more problematic at the nursery stage. It causes a dark brown or black rot at stem base of seedlings resulting in death. It is common in overcrowded and or over-watered nurseries.

Control: Use of fungicides, avoid overcrowding and over watering of seedlings.