Brassicas are a family of crops that are very varied and include all the cabbages and cauliflowers, turnips, broccoli, Brussels sprouts and kales.
They also cover some ornamentals too like wallflowers Erysimum that are happy in more alkaline soil. Although brassicas are varied there are some characteristics that they all have in common.

Get the right soil environment (pH)
Before planting brassicas create a soil environment ideal for them to take up maximum nutrients for healthy growth. The pH of the soil is all important, and all brassicas favour a neutral to alkaline soil. Make sure the soil has an adequate level of alkalinity by adding lime . For particularly acid soils you’ll want 1.3-1.8kg per square metre. For soil that is more neutral, you’ll want to aim for about 0.4-0.6kg per square metre. With a corrected alkalinity  your brassica plants will perform much better and give you fuller lusher plants, less susceptible to diseases like club root.

Get the right soil environment (soil density)
Brassicas favour compacted and firm soil so make sure the plants are well anchored. If you are preparing the soil do so a few months before planting. This will give the soil time to settle and consolidate which is more favourable for growing brassicas.

Grow the right crop in the soil beforehand
For leafy brassicas make certain that the plants have access to as much nitrogen and nitrates as possible. A natural and organic way of doing this is by growing nitrogen-fixing crops the year before. Nitrogen-fixing plants include legumes like peas and beans. The nodules on the roots of peas and beans allow nitrogen to get to the soil and build it up. Try a crop of broad beans the year before. They are easy to grow and mature early.

Don’t grow brassicas in the same spot year after year
Planting in the same spot year after year can spell trouble for brassicas. Each year there is an increased risk of a build-up of soil borne pests and diseases.
One such disease is club root which causes discoloured leaves and wilting when the brassica plants are growing. Chafer grubs are a notorious pest that increase in numbers the longer a particular crop sticks around.

Protect brassicas with netting and collars
Brassicas attract birds such as woodpigeons and doves. The leafy varieties like spring cabbage attract cabbage-white butterflies too that lay eggs of the underside of leaves. You can prevent this by covering with netting. Brassicas are also victim to cabbage root flies whose maggots attack the roots in spring and summer. You can apply collars to the base of young plants. The eggs simply dry up and die on this protective barrier. Alternatively you can apply a solution containing nematodes that is a biological means of controlling cabbage root fly and pests of other crops.

Water and feed brassicas
In the previous season dig in plenty of organic matter to improve the soil texture and to introduce nutrients into the soil. Add general purpose fertiliser when digging in organic matter. Just after planting treat the soil to a layer of mulch.  This has a dual-purpose of conserving water in the drier summer months and feeding the growing brassica plants. Don’t allow mulch and brassica plants to be in direct contact. Water plants daily from planting and twice daily during hot periods in summer.