Itinerário técnico
Um guia de cultivo passo a passo, da sementeira à colheita.
Sow in trays or a seedbed one centimetre deep, ten to twelve weeks before transplanting, or sow direct and thin later. Germination takes ten to fourteen days. Transplant when the plant is the thickness of a pencil, trimming a third of the leaves and roots, and plant shallowly with the bulb at soil level. Planting the bulb too deep is a classic mistake and rots the neck.
It wants loose, free draining soil with no fresh manure, at a pH between 6.0 and 7.0. Waterlogged soil rots the bulb easily, so a raised bed is a good option on heavy ground. Three to four year rotation away from garlic, leek and chives.
It grows between 13 °C and 24 °C, and bulbing is driven by day length rather than temperature. This is the key to the whole crop: a short day variety planted in Germany never bulbs, and a long day variety planted in the Algarve bolts without swelling. Always choose varieties suited to the latitude you grow at. It adapts to most of western Europe. On the Portuguese coast and in southern Spain use spring and autumn and avoid the peak of summer. Inland in Iberia water more through the dry months. In France and Germany the natural season is spring and summer, sowing once the soil has warmed steadily. In Italy the same rule applies as in the rest of the Mediterranean: spring and autumn in the centre and south, spring and summer in the north.
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.
Water regularly while the leaves are growing and stop watering once the bulbs are formed and the tops begin to fall over. Watering at the end of the cycle is the mistake that ruins storage: it gives bulbs that rot in store within weeks.
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.
Onion fly lays at the neck and the larva burrows into the bulb: cover with fine mesh and do not leave crop debris in the bed. Thrips cause silvery patches on the leaves in hot dry weather and are treated with potassium soap and occasional overhead watering. Nematodes distort the plant and call for a long rotation.
Onion downy mildew covers the leaves with a violet felt in cool damp weather and is the main problem on the Atlantic coast. White rot attacks the base of the bulb and persists in the soil for many years. Neck rot appears in store, from badly cured bulbs. Prevention means generous spacing, watering at the base, drainage and thorough curing in the sun before storing.
Lift when half to three quarters of the tops have fallen over and dried naturally. Do not bend the tops over by hand to hurry things, because that shortens storage life. Lift in dry weather, leave in the sun for two or three days, then cure for two or three weeks somewhere airy and shaded with the tops still attached. Well cured, it keeps six to eight months. Allow about 100 to 120 days from sowing to the first harvest of this variety. The reference colour is dark red, and that is what tells you it is ready.
