CABBAGEBrassica oleracea, B. napus och B. napa
The cabbage plants belong to the cruciferous family and have an exciting wealth of shape and form. Their origin is still considered to be one single species, a leaf cabbage (Brassica oleracea var. silvestris) growing wild on the beaches of Southern and Western Europe. Its closest relative among the cultivated sorts grown now is Kale.
All kinds of cabbage grown now, commonly, prefer to grow in a little heavier, well drained soil with a good supply of nutrients. They are therefore grateful for good compost and natural and green manure. The cabbage plants like a relatively high content of moisture in both soil and air and thus grow best in late summer and autumn. If it is impossible to water the plants during dry periods, it is a good idea to cover the ground with organic materials to keep it moist and free of weeds.
It is important to keep the PH-value quite high because of the risk for clump-root disease, a devastating fungal disease which prefers wet soils and a low PH-value. The spores of the fungus survive for many years, so avoid growing cabbage plants and other cruciferous plants, for instance radish and black radish, in the same place more often than every 6 years. One must wait for at least 6 years before cabbage plants can be grown again after an attack of clump-root disease. Growing green manure and mixing in organic materials and compost aid the soil in taking care of the fungus spores in the meantime.
The cabbage plants have many enemies which are not visible to the naked eye. There are a number of fungi, bacteria and viruses, which harm the plants more or less seriously. The choice of the correct sort, crop rotation and uncontaminated soil in sowing boxes and hot beds are the best methods of eluding these invisible threats. The attacks can be diminished and sometimes avoided by spreading lime and algomin before sowing and spraying the soil and seedlings with extracts of algae or a broth of horse-tails. Burn sick plants! Do not put them in the compost.
Several kinds of insects also attack cabbage plants, chiefly the larvae of the cabbage-fly and the cabbage butterfly. The cabbage moth is also a scourge in some years. Earth-fleas can cause problems as well, especially to directly sown cultivations. The most important measure to keep the attacks under control is to give the plants as good a start as possible, planting them in moist soil with lots of nutrients. The plant is weakened by drought, which is favourable to insects and diseases. Keeping the soil moist all the time by watering it at least once a week is a good way of making things inhospitable to cabbage-flies and earth-fleas. A nettle-water shower and spraying with extracts of algae also strengthen the plants and their resistance to disease making it easier for them to withstand an attack.
Co-cultivation with aromatic herbs, the onion-family, celeriac, broad beans, marigolds and Tagetes also helps against attacks. Early sowing of lettuce cabbage, May turnips or radishes as a capture crop tempt the majority of the cabbage-fleas and cabbage moths and those plants are discarded accordingly. Covering the ground around the plants with strong smelling herbs keeps the fleas away too.
Butterflies, flies, larvae, and fleas detest repeated powdering with lime, algomin, wood-ash, rock-flour, or salt on damp leaves and around the throat of the root as well as spraying with water of common tansy, wormwood or soap. When there are serious and persistent attacks poisonous extracts of plants can be used, pyrethrum and rotenone. A bacterial preparation, Bacillus thuringiensis, works against larvae of butterflies in southern Sweden. A boring and expensive, but a proportionately simple way of avoiding attacks from many kinds of insects and also four-legged animals is to cover with a fibre-cloth, but if there are lots of wintering insect eggs in the ground the cloth has the opposite effect. Birds and various predatory insects are shut out and the vermin come to a ready laid table.