A giant kohlrabi, with a white to light-green bulb that grows without losing its tenderness.
About the variety. Slow-growing, the bulb can reach 8 kg and still remain tender and flavourful; the sowing date and planting spacing influence the final size.
Itinerário técnico
Como cultivar kohlrabi superschmelz?
Um guia de cultivo passo a passo, da sementeira à colheita.
pH ideal 6.5 to 7.5Temperatura ideal 15 to 20 °CCompasso 25 cm in the row, 25 to 30 cm between rows
Sementeira
Sow direct one or two centimetres deep in rows and thin to fifteen to twenty centimetres between plants. It can also be raised in trays and planted out at three to four weeks, but without burying the stem, because the swelling must sit above the soil. Sow in succession every three weeks for a continuous supply. At about 60 centimetres tall, this variety grows well in a pot twenty centimetres deep with drainage holes. Use a pot at least twenty five centimetres deep with drainage holes, and expect to water more often, because a pot dries out far faster than open ground.
Solo
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. It likes settled rather than fluffy soil: firm the ground lightly around the plant after transplanting. Minimum four year rotation away from any other brassica, radish, turnip and rocket included.
Clima
It grows best in cool weather, between 15 °C and 20 °C, and is slow: it needs a hundred and ten to a hundred and twenty days from transplanting. Strong heat makes the swollen stem fibrous and hot tasting. The Portuguese coast offers close to ideal conditions and allows harvests over much of the year. Inland in Portugal and Spain, concentrate the crop in autumn, winter and early spring, because from June onwards heat and long days push it to bolt and turn bitter. In France it grows easily from spring to autumn, and in Germany the whole summer works because it is rarely too hot. Light shade over the middle of the day extends the harvest in any warm climate.
Fertilização
Its needs are moderate. One to two kilos of mature compost per square metre worked in before sowing covers most of the cycle. If the leaves pale, one watering with a balanced liquid organic feed halfway through is enough. Never use fresh manure, which burns roots and encourages disease.
Rega
Water regularly with no gaps. Any check from lack of water toughens the swollen stem and turns it woody, the commonest fault with this crop. Steadily moist soil gives a tender sweet product.
Controlo de Infestantes
Hoe often and always shallowly, because the roots are short, near the surface and break easily. The best method is to prepare the bed two or three weeks in advance, let the first flush of weeds germinate, remove it and only then sow: that gives you a decisive head start. A thin layer of sieved compost between the rows greatly reduces later work.
Controlo de Pragas
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 almost all of these problems at once.
Doenças
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 spots and downy mildew a grey bloom on the underside of the leaf; both like humidity, so space 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.
Colheita
This giant variety reaches fifteen or twenty centimetres across and two kilos or more without going woody, so let it grow without hurry. Harvest when the lower leaves begin to yellow or before hard frosts; it keeps for several weeks somewhere cool. Cut the root below the swelling and use the young leaves too, which cook like cabbage. Allow about 110 to 120 days from transplanting to the first harvest of this variety. The reference colour is whitish green, and that is what tells you it is ready.
