These days watercress is a proven antibiotic, too, so it is interesting that Hippocrates is reputed to have sited the first hospital by a stream in order to have it in ready supply. Modern cultivation is based in beds around freshwater springs. The main British season is from October to May.

Varieties
Thick steams indicate that the watercress is older and will have a very strong flavour. Wild watercress can still be found growing in clumps among the rocks in clear-running streams and brooks.

Serving suggestions
During the industrial revolution, freshly cut watercress and bread was a typical breakfast for workers, and watercress sandwiches - perhaps with the addition of eggs, prawns or salmon - are still a nourishing treat. Watercress soup, made with potatoes, is one of the best-known uses. It can also be made into baked savoury mousses and quiches. In salads its peppery flavour works well with baby potatoes, chicken, tomatoes, orange, pears, blue cheese, goat's cheese, and bacon. Watercress makes an easy garnish for grilled steak or lamb, its mustardy taste helping to cut through the fattiness of the meat. You can also treat it like a herb, adding it finely chopped to butter sauces or mayonnaise, or stirring a handful into noodle dishes.

How to prepare
As it is grown in water, watercress is usually very clean on purchase. Discard any wilted, yellow or bruised leaves or stems. Remove any string-like roots and use your fingers to pick the sprigs from any particularly large stems. Don't remove the stems entirely, however, for that's where most of the flavour is.