Brassicas are in a family of crops that are very varied – they include all the cabbages and cauliflowers, turnips, the broccolis and calabrese, 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.
When preparing the soil beforehand you can test the pH using a specialised kit. Then you can 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 clubroot.
Get the right soil environment (soil density)
Brassicas favour compacted and firm soil so it pays to make sure the plants are well anchored. If you are preparing the soil, do sow 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 like cabbage, you’ll want to 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 – easy to grow and achieving an early harvest.
You could even grow a crop of green manure, the season before of clover or winter tares. Once they’ve produced a thicket of green stems and leaves, simply dig into soil and the they’ll add essential nutrients into the soil.
Don’t grow brassicas in the same spot year after year
Planting in the same spot year after year can spell trouble for brassicas. Despite the convenience of designating a part of the plot each year for a certain crop, it’s just not worth it. Each year there is an increased risk for 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. Yes, the problem is surmountable but prevention is better than cure.
Chafer grubs are a notorious pest that increase in numbers the longer a particular crop sticks around.
Protect brassicas with netting and collars
Many of the brassicas offer a tasty treat for 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. The resulting caterpillars that hatch then have a ready source of food – your crop!
You can prevent this attack from garden pests by providing netting- it’s a natural and organic way of keeping the pests away.
Brassicas are also victim to cabbage root flies whose maggots attack the roots in spring and summer. This results in a poor crop of brassicas that may wilt and die. You can nip the problem in the bud though by applying collars to the base of young plants. The eggs simply dry up and die on this protective barrier.
Alternatively or additionally 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. To top up and really put the young plants in good stead, add general purpose fertiliser when digging in organic matter.
Just after planting, treat the soil to a layer of mulch (a general purpose compost is fine). 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 – leave a little space around the plants.
Water plants daily from planting and twice daily (morning and evening) during hot periods in summer.