Watercress grows wild in rivers and streams all over the UK, and here in Cornwall’s balmy climate, it’s still going strong. It’s a very delicious and nutritious plant and easily identified but care should be taken before picking and eating it, especially if it’s growing near where there are cattle.
Unfortunately, watercress is often inhabited by water snails that carry the cysts of liver fluke, a waterborne parasite that is deeply unpleasant. Apparently, the cysts cannot survive for very long out of water, so if you are careful just to pick the tallest tips of the plant, it should be safe. The only way to be certain though is to cook it thoroughly, so it’s probably best to stick to watercress soup or sauce if you’re going to pick it wild.