When the weather gets cold, the leek takes the spotlight as one of the stars of the winter garden. You can pick them fresh from the garden to add great flavoring to any recipes that normally use onions or enjoy them as the featured vegetable of your meal.
Though nowadays the leek is considered one of the more refined members of the onion family, for most of its history it was an everyday staple of the common people. This was partly due to the fact it was easy to grow and could be left in the ground all winter, even at -10 F. But it was surely also appreciated for its sweet and delicate flavor. It is milder and easier to digest than other onions and was very important for enhancing the bland staple foods that made up the European peasant diet for centuries.
Perhaps the leek’s most common use was in making soup, no doubt because when cooked it has a slightly mucilaginous quality, which make soups smooth and creamy. Notable leek soups have been prepared in Scotland, Wales, France, Spain, Italy, Greece and Turkey. The ingredients in Scottish Cock-a-leekie soup hint at its humble peasant origins. You don’t get much more basic than leeks, chicken stock (the bird was boiled in the soup for a couple of hours and then eaten separately) and barley (later potatoes were added). The more refined vichysoisse, involving lots of cream, is a 20th century transmutation of a French leek soup and was invented by a French chef at the Ritz Carlton in New York (not exactly a peasant hangout).
From the gardeners viewpoint the best thing about leeks is that they are so easy to grow. Unlike the related onions and garlic, you don’t have to worry about day length and its effect on bulb development. Leeks are a biennial and so, unlike many annual vegetables, they have little inclination to bolt or turn bitter in their first year. They just keep getting bigger. In mild climates like we have in California, they will continue to grow right through the winter and still be good to eat in early spring. In colder climates they won’t grow much in the winter, but they can be left in the ground for months, even at below freezing temperatures. The outermost leaves might get a little slimy, but the interior will be perfectly fine (mulch can help to protect them and keep the ground from freezing). They will eventually bolt in spring when the days lengthen and the weather warms, but you will probably have run out of Leeks to harvest before this happens.
If any leeks do get around to bolting you can admire the spectacular flowers and then save their black seeds for planting next year (they are cross-pollinated, but there are unlikely to be too many leeks flowering around about). The flowering plants also produce offsets, which can be used to grow new plants (these are known as leek pearls).
To grow a winter Leek crop you must choose a winter variety (these are hardier than summer varieties) and start the seeds in mid-summer (they are fairly slow growing). This gives them plenty of time to grow so they are close to maturity by the time cold weather arrives and the day length drops below 10 hours. The plants will then stay in good condition for eating all winter and will even continue to grow slowly. The Leeks you grow for summer use can simply be left in the ground into the winter, to be harvested as needed for the kitchen. These varieties don’t tend to be as hardy as the preferred winter types, so eat them first.