Itinerário técnico
Um guia de cultivo passo a passo, da sementeira à colheita.
Always sow direct where it is to grow, one or two centimetres deep in rows, because transplanting deforms the root. Germination takes four to seven days. Thin early to ten or fifteen centimetres between plants, once the seedlings have two true leaves. Failing to thin is the number one reason for harvesting turnips the size of a finger.
It wants loose, deep, stone free soil with no fresh manure, at a pH between 6.0 and 7.0. Compacted or cloddy soil gives forked, deformed roots. Work the ground to twenty five centimetres and break the clods down well before sowing. Rotate away from other brassicas.
It is a cool weather crop, ideal between 10 °C and 20 °C, and the root sweetens after a spell of cold. Strong heat makes the root hot tasting, fibrous and hollow inside. This is a cool season crop and heat is its main enemy. 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. In Italy follow the Iberian calendar in the centre and south, concentrating the crop in autumn and winter, and the French calendar in the north, where the Po valley summer rarely makes it bolt too early. Light shade over the middle of the day extends the harvest in any warm climate.
Do not use fresh manure or strong nitrogen feeding: that gives forked, hairy and tasteless roots. Use a bed that was composted for the previous crop and top up potassium only, with sieved wood ash, which improves sweetness and keeping quality.
Water regularly and without gaps. Alternating drought and heavy watering splits the roots and makes them fibrous and hot. Steadily moist soil gives tender sweet roots.
The crop germinates slowly and is completely overrun by weeds in the first weeks, which is the number one cause of failure. Prepare the bed in advance, clear the first flush of weeds before sowing and mark the row with radish, which comes up within days and shows you where to hoe. Hoe shallowly between the rows and never pile soil over the crown.
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 soil that is never acid: if the pH drops below 6.0, lime it back up to the top of the range given for this crop. 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.
Harvest young, when the root is five to eight centimetres across: that is where the flavour is. Past that it goes fibrous, hollow and hot. Pull by the leaves after watering, while the soil is damp. The young leaves are also good eating and should not be wasted. Allow about 60 to 70 days from sowing to the first harvest of this variety. The reference colour is yellow, and that is what tells you it is ready.
