Claire Hart of Suttons explains how to sow, grow and harvest brassicas.

April may be full of showers, but its also the ideal time to start planting your winter brassicas, sowing from April through to August for a continuous supply. Broccoli, Brussels sprouts, cabbages, kale, leeks and parsnips are hardy vegetables and will stand through the winter. Rich in iron and folic acid, they are an autumn /winter staple, following on well from the summer produce. Most brassicas are relatively easy to grow although cauliflowers with their wonderful white curds, do require a little more care.

- Soil preparation

All brassica crops grow best in partial shade, in firm, fertile, free-draining soil.

Hopefully you prepared your soil back in autumn, having already removed any stones and worked in plenty of well-rotted manure or compost.

Brassicas do not like acidic soil, so add lime to the soil if necessary, aiming for a pH of 6.5-7.5.

- How to sow seeds

Nearly all brassicas should be planted in a seedbed or in modules under glass and then transferred. Seeds should be sown thinly, as this reduces the amount of future thinning necessary and potential risk from pests.

Sow seeds 1.25cm (1/2in) deep and rows should be spaced 15cm (6in) apart.

Once the seeds have germinated, thin the seedlings to 7.5cm (3in) between each plant.

Cabbage and broccoli seedlings are ready for transplanting when they're between 6 and 8cm high (2.5-3in). Brussels sprouts and kale should be 15cm (6in).Water the day before moving, and keep well watered until established.

Space the plants according to the instructions on the seed packet. It can vary from 30cm for small cabbages to 75cm for Brussels sprouts.

- Aftercare

Make sure the soil is adequately limed and well drained, and do not plant cabbages in the same place the following year.

Rotate your crops annually to avoid disease. Don't grow brassicas on the same plot more often than one year in three, as moving the crop helps avoid the build up of soil pests and diseases.

Club Root is once such serious plant disease, caused by the soil-borne ‘virus’ plasmodiophora brassicae which infects susceptible plants through root hairs. Club root will reduce yields and can cause total crop failure. It cannot be controlled by Fungicide and can live in the soil for up to 20 years! Affected plants need to be removed and destroyed.

So this is why Club Root resistant veg varieties are so important.

Brassicas are a particular favourite of birds so use a deterrent to stop them picking off seedlings. CDs on string can be effective. They're also susceptible to attack by the caterpillars of the cabbage white butterfly. Try covering crops with a crop protection mesh. It keeps the butterflies out, so they can't lay their eggs on the plants.

- Harvest and storage

Harvesting time is dependent on crop type and variety. From July onwards, summer cabbages, cauliflower, kohl rabi and green broccoli are all ready.

Harvest by cutting close to ground level with a sharp knife.

With cabbages, lift the entire plant to reduce the risk of club root.

With broccoli, harvest when the flower shoots are well formed, but before the small flower buds have opened. Timing is important, as once in flower, the shoots are woody and tasteless.

From October well into the following year, winter and spring cabbage, Brussels sprouts, early and late varieties of broccoli, autumn and winter cauliflower, kale, kohl rabi, swede and turnips are all ready.

Begin harvesting Brussels sprouts when the sprouts at the base of the stem have reached the size of a small nut and are tightly closed. Cut them off with a sharp knife, disposing of any opened sprouts and yellow leaves. Only remove a few sprouts at a time from each individual stem.

With kale, start harvesting at the crown of the plant from November onwards, removing a few young leaves at a time. This stripping of the crown encourages the development of succulent side shoots to harvest between February and May.