Watch your ­cauliflowers’ stress levels

Although many aspects of cauliflower production are similar to ­cabbage and broccoli production, some aspects require particular attention.
Issue date 15 June 2007

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One of these is basic fertilisation. The nitrogen requirement of cauliflower is slightly lower than that of cabbages, which allows the leaves to grow at ­maximum vigour for better ­protection of the curd in hot ­conditions. It is much easier to produce cauliflower in cool weather c­onditions. Although varieties adapted to warmer summer conditions can be rather ­successful, all it takes is a brief period of stress to turn the crop into a disaster.

Good on the outside, rotten on the inside

At first glance, the size and colour of the leaves may seem intact, but when ­harvested the curds could be ­discoloured or hairy. In this case, ­previous signs of wilted leaves during a heat wave might have been overlooked. This is what makes growing cauliflower a lot ­different from growing cabbages.

The cabbage leaves that are harvested can take a knock once in a while which will only reduce the yield, but when the flower buds of cauliflower suffer stress, the edible part of the plant is ruined. Heat stress will not only set the plants back in summer but also magnify any other stressors, such as insufficient nitrogen levels or a high population of diamondback moth larvae.

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Damage in the early stages

Buds that constitute the curd already develop many weeks before ­harvesting, which means that stress can adversely affect these plants at a very early stage. Vigorous, uniform growth is crucial right up to harvesting.

Effective nitrogen application

As with cabbage, the first nitrogen side dressing should be applied from three to seven days from transplanting and the ­second application two to three weeks later. A third application is optional and will depend on the growth rate and colour of the leaves. Modern varieties mature much earlier and the third dressing is often unnecessary. In the end experience will be the judge of what is necessary, as so much depends on other factors such as the soil ­condition, basic fertiliser and leaching.

Sprinklers for crispy crops

Irrigation can effectively cool down the ­temperature to a tolerable level during a heat wave. When soil is fairly moist, light, frequent irrigations can keep up high evaporation to cool off crops. In this case, sprinklers are safer than drip irrigation.
These measures should be taken to reduce stress, as we are ­growing a crop out of season. – Bill Kerr

Contact Bill Kerr on (016) 366 0616 or e-mail [email protected].