There are a number of varieties of cabbage, they mature at different times in the year, and have subtle differences in flavour. They are usually sown thinly in a row then transplanted to their final position when they are about 15cm tall - space about 50cm apart, all around. The young plants must be firmed in well to prevent them from falling over later as they develop - this results in smaller, looser heads.
Summer cabbage are the earliest to be sown from March to May, and are ready to harvest from July to November.
Winter and Savoy Cabbage are sown in April and May, transplanted in July and are ready from November to January.
Spring Cabbage are sown in July and August, transplanted in September or October to grow through the winter for cropping the following spring. They are planted closer than the other varieties (about 15cm apart) as they are usually harvested before they develop a hard head. Harvest alternately to allow remaining plants to develop.
They require plenty of water, one or two nitrogenous feeds during the growing season, and benefit from the addition of about 50g/m2 of lime before planting.
Pests: Cabbage Root Flies lay eggs at the base of the stems and the larvae devour the roots. 15cm discs of thick card or matting fitted snugly around the stem at soil level, prevents the hatching larvae getting down to the roots. The Cabbage White Butterfly caterpillars can turn the leaves to lace. Also Slugs and Snails can reduce young plants to stumps virtually overnight as can the attention of Pigeons. Placing a ring of lime around the plant discourages the slugs and supplies the alkaline conditions preferred. Butterflies can be kept away with a fine mesh net, which should be held away from the plants or they will lay through it. It will also keep the Pigeons at bay. If the attack is not too severe the plants should recover and the hard heads will not be affected.
Grey-green Cabbage Aphids are very unsightly and reduce the vigour of the plants. They can be rubbed off by hand or washed off with a jet of water.
Diseases: Clubroot is the main problem. It causes the roots to swell, they cannot take up as much water or nutrients and secondary rots can invade - the liming discourages it. Raising the plants in pots to establish a good rootball and using a resistant variety, may overcome the problem. Some growers remove a pocket of soil and replace it with a mixture of garden compost, fertilizer and some lime.
Growing the crop under a tunnel of Enviromesh or similar product, can avoid most of the pests, apart from slugs which always find a way in. The fine mesh can be supported with hoops of stout wire or flexible plastic piping to hold it away from the crop, and anchored around the edges with stones or bricks to ensure there are no gaps to admit the root flies or butterflies. The tunnel should be used from first planting out and high enough to allow for the final size of the plants, with minimal disturbance as the pest could sneek in at any time the canopy is raised.
The other Brassicas, eg. Cauliflower, Broccoli, Brussel sprouts and Kale are grown in a similar way.