Article originally published 8th March 2018. Updated 7th March 2023.
On the coastal cliffs of southern England grows a leafy, straggly plant that is the wild ancestor of much of the supermarket veg aisle. Broccoli, cabbage, cauliflower, kohl rabi, Brussels sprouts and kale were all derived in Europe from the wild cabbage – Brassica oleracea. It is rare for a crop type to be native to the UK and even more unusual for one species to spawn so many diverse crop types. The name colewort once covered all leafy, edible brassica plants but they developed new names as the forms became more distinct – some bred for tightly packed leaves (cabbages and sprouts) or swollen stems (kohl rabi) or tight heads of flower buds (cauliflowers and broccoli). Kale is closest in appearance to the wild plant and was the first of these to be cultivated.
Large family
As befits an ancient crop, kale comes in a variety of shapes and colours. Most commonly seen are those with green, tightly curled leaves or the long, dark, blistered leaves of ‘Cavolo Nero’, the Tuscan black kale. Both of these can be enjoyed from early autumn throughout the winter. There is also a dark red leaved version of the curly green type, which looks beautiful in the garden but I find that the leaves go tough quickly as the winter weather bites. There are flat leaved types that are probably closest to their wild ancestor. In parts of Spain and Portugal it is known as ‘Couve’ and used in soups; the similar looking collard greens are eaten in the Southern US, cooked with ham or bacon. Some of these types are perennial – look for the varieties ‘Daubenton’ or ‘Taunton Dean’. These will make large plants that can be harvested year round and are easily multiplied by breaking off young shoots in spring and potting on. A final subgroup are the Siberian kales (Brassica napus var. pabularia), which have blue/green leaves with ruffled edges, tinged with red. They are actually more closely related to oilseed rape and are much more cold-tolerant – these were the only outdoor kales to survive the winter of 2010, with six frozen weeks and temperatures down to -15C. Despite this, the leaves are more tender and less bitter than the true kales so these are ideal for use, raw shredded in salads.
Sowing and growing
Kale can be enjoyed more or less-year round if you so desire. Seeds sown in spring can be cut young for salads or left to grow on at a wider spacing for mature plants. For a winter harvest, seeds can be sown as late as July as they are quick growers. They will sit though the worst winter conditions, growing new leaves whenever the temperature is over 5C.
Leaf munchers
The only major pests are pigeons and cabbage white caterpillars. Nets with gaps no larger than 1cm will suffice for both pests and as soon as the butterflies stop laying eggs in late summer, the pigeons start getting hungry, so I leave them covered all year. The caterpillars can strip the plants down to the ribs but if it is any consolation, once the caterpillars go, the plants usually regrow in time for winter! Scottish crofters up as far as the Shetland Islands would have all had their kailyards, which were sheltered stone walled enclosures to protect the plants from winter gales. If you live in a windy area, some stakes will probably suffice as the plants can grow quite tall.
On-trend
Kale makes a great cut and come again salad crop, either indoors or out. However, for the ultimate in trendy eating, you can grow kale ‘micro greens’ – even through the winter if you have a south-facing windowsill. Fill a seed tray with a couple of inches depth of potting compost. Scatter a mix of kale seeds over the surface, lightly cover with compost and keep watered. In 2 to 3 weeks you can cut the leaves with scissors, leaving the young growing point intact to grow a second flush of leaves. Eaten either raw, steamed or chucked by the handful in the juicer, this primitive crop is very much in the present and on-trend.
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