Choose watercress with large, dark green leaves. Reject slimy or yellowing specimens, and remember that even the freshest watercress will last only a couple of days in the fridge.
Bunches of watercress weigh about 100 g (3 1/2 oz). Supermarket bags weigh 75 g (3 oz), about the same as a bunch, allowing for the fact they have less waste.
Watercress and mustard are from the same family.
Although wild watercress grows in many parts of Britain, it may carry liver fluke, so stick to cultivated watercress.
Watercress was once the only leafy salad available through much of the winter. It must have been a welcome relief from root vegetables and cabbage. Growing wild in streams throughout most of Britain, only when the weather became so cold that the beds flowing with water iced over did supplies dry up.
Watercress makes wonderful sandwiches, a great accompaniment to soup, especially if you use cheese bread. The crisp mus-tardy leaves are fabulous with roast meat, soaked in the dark caramelized roasting juices.