Itinerário técnico
Um guia de cultivo passo a passo, da sementeira à colheita.
Sow in trays one or two centimetres deep at 15 °C to 20 °C. Germination takes five to ten days. Transplant at four to six true leaves, about five weeks later, setting the plant in up to the first leaves and firming the soil well: a loosely planted cabbage rocks in the wind and never hearts up properly. Water well on transplanting day and fit the cabbage root fly collar straight away.
It wants firm, deep soil, rich in organic matter and never acid: the ideal pH is between 6.5 and 7.5, and acid soil invites clubroot. Unlike root crops, this family likes settled rather than fluffy soil, so firm the ground lightly around the plant after transplanting. Minimum four year rotation away from any other brassica, radish, turnip and rocket included.
It is a cool weather crop, at its best between 15 °C and 20 °C, and its flavour improves after a frost. Strong heat halts head formation and pushes the plant to bolt. It takes cold well and a light frost even improves the flavour, which makes it an autumn and winter crop in southern Europe. On the Portuguese coast it grows through the whole winter without trouble. Inland in Portugal and Spain night frosts do it no harm, but the summer there is too hot and dry for it. In France and Germany it is a summer and autumn crop, and in a cold winter a fleece or a low tunnel keeps the leaves in good condition well into the cold season. In Italy it is an autumn and winter crop in the centre and south, as in Portugal, and a spring and autumn crop in the north, where the Po valley winter is too hard to leave it outside unprotected.
This is a hungry crop. Work two to three kilos of well rotted compost or mature manure into each square metre before planting and add a handful of bone meal or wood ash to top up phosphorus and potassium. Once growth is away, feed with a liquid organic fertiliser every two or three weeks, moving from a balanced formula to a higher potassium one as cropping begins. Avoid excess nitrogen, which gives lush leaves, a poor crop and a lot of aphids.
Water regularly and generously, because the leaves transpire heavily. Irregularity is what splits formed heads: after a dry spell, one heavy watering cracks the cabbage open. Water at the base and mulch the soil with straw to smooth out the swings.
Hand weed in the first weeks, while the plant is small and loses every contest for light and water. Once it is established, mulch with five to seven centimetres of straw, dried grass or leaves: it holds weeds back, keeps moisture in and stops rain splashing soil onto the lower leaves, which is how most diseases begin. Always hoe shallowly so you do not cut the roots running just under the surface.
This family has many pests and prevention beats cure. Flea beetle, a small jumping beetle, riddles young leaves with round holes in hot dry weather: keep the soil moist and cover with fine mesh from sowing. Cabbage white caterpillars and diamondback moth eat the leaves from within: apply Bacillus thuringiensis while the caterpillars are small and check the underside of the leaves every week. Cabbage root fly lays at the collar and the larva destroys the root: a cardboard or felt collar around the stem stops the egg laying. Grey cabbage aphid forms waxy colonies on the shoots and is dealt with using potassium soap. A fine insect mesh put on at planting solves practically all of these at once.
Clubroot is the most serious disease: it deforms the roots, the plant wilts, and the fungus persists in the soil for close to twenty years. Prevent it with a four to five year rotation, good drainage and a pH above 7.0, corrected with lime. Alternaria makes dark concentric leaf spots and downy mildew a greyish white bloom on the underside, both favoured by humidity: space the plants well and water at the base. Black rot enters at the leaf margins as a yellow V and is carried by seed and irrigation water. Clear all crop debris at the end and keep it out of the compost heap.
Cut when the head feels firm in the hand. Cut at the base with a knife and leave the stump in the ground with a few leaves: many varieties push out side shoots that give a smaller second crop. A head that starts to split should be cut at once. It keeps for several weeks somewhere cool and dark. Allow about 150 days from transplanting to the first harvest of this variety. The reference colour is white, and that is what tells you it is ready.
