Growing Cavolo nero

Cavolo nero is a type of kale from Italy, mainly from Tuscany, which is why it also goes by Tuscan kale, black kale or lacinato kale. Instead of curly leaves, it grows long, narrow, dark blue-green, blistered leaves on an upright stem. Over time the plant looks like a small palm tree. Unlike most brassicas, cavolo nero handles summer heat well, and it doesn't need frost to taste good. It usually gets through frosts down to about minus 10 degrees without damage. Because of its shape, some people grow it as an ornamental in large pots.

Sow cavolo nero from April to June in pots or a seedbed. The seeds germinate from as low as 2 degrees, fastest at around 20 degrees. After about four weeks, once the young plants have three or four leaves, they can go into the bed. Older transplants tend to bolt later on. For a long harvest into winter, plant out in June or July, so cavolo nero fits in nicely after early potatoes, peas, French beans or lettuce. Space the plants 50 x 50 cm, tall varieties 75 x 50 cm, and add well-rotted compost when planting. The seeds stay viable for at least six years.

Cavolo nero does best in full sun, but it will put up with a bit of shade. Deep, humus-rich loam that holds water well is ideal. On light, sandy soil it works if you add plenty of compost. The soil should be well limed, as a pH of around 7 makes life hard for clubroot. In a container, cavolo nero needs at least 10 litres of compost and regular watering.

The most widely grown variety is the old Italian Nero di Toscana, also sold as Negro Romano or Cavolo nero. It grows to about a metre tall, and noticeably taller in its second year. There are also newer varieties such as Black Magic or the hybrid Raven. There's not much difference between the different strains.

Cavolo nero is a heavy feeder. Work plenty of well-rotted compost into the bed before planting and feed again a few weeks later with a homemade plant tea. Regular feeding and, above all, an even supply of water are key to good leaf growth. Mulching with grass clippings helps a lot, and until then you should loosen the soil regularly. Insect mesh from planting onwards keeps most pests away. Tie tall plants to a stake before winter so wind and snow don't push them over.

Cavolo nero is as tough as curly kale, but it's not completely trouble-free. On soil with clubroot it fails just like other brassicas. So keep four years between it and other crucifers, and make sure the soil has enough lime.

The main pest on cavolo nero is the cabbage whitefly, a tiny white insect that gathers in huge numbers on the undersides of the leaves in warm late summer and autumn. Its sticky honeydew turns black with sooty mould. Netting from planting onwards and clearing away old brassica stalks help most, and you can also blast them off with a strong jet of water.

Caterpillars of the cabbage white, diamondback moth and cabbage moth eat holes in the leaves, and the cabbage root fly lays its eggs at the base of young plants. Because cavolo nero also grows through summer, flea beetles hit it especially hard in hot, dry weeks. A fine insect mesh reliably protects against these pests too, as well as against the mealy cabbage aphid.

In autumn you'll sometimes see a white coating on older leaves that you can wipe off. That's powdery mildew, which often affects cavolo nero and curly kale. In cool, wet weather, white pustules can appear on the undersides of the leaves. That's white rust.