Thought For Food: The new rocket

t's delicious, really good for you, 'purifies the blood and keeps away the rheumatics for a year'. Darina Allen can't recommend watercress highly enough

Watercress is the 'new rocket'. After decades of being pushed to the edge of the plate as nothing more than a decorative garnish, watercress is suddenly the hippest 'new' ingredient, enjoying a huge renaissance as diners discover its not just a bit on the side. Chefs can't get enough of it and they are using their creativity to use the peppery little salad leaf in a myriad of different ways. It was all over California on a recent visit. In New York, it features on virtually every restaurant menu. Pick up an Australian food magazine and you'll find the same – everyone going crazy for the peppery green leaves which are reported to be rich in beta-carotene, iron and vitamin C.

Watercress is bursting with goodness; its health benefits have been known since ancient times. Greek general Xenophon insisted that his soldiers ate it as a tonic, and Hippocrates, the father of medicine, chose the location of his first hospital because of its proximity to a stream so that he could use only the freshest watercress to treat his patients.

Gramme for gramme, watercress is a better source of vitamins C, B1, B6, K and E, iron, calcium magnesium manganese and zinc than apples, tomatoes and cooked broccoli. It's got more iron than spinach, more Vitamin C than oranges and more calcium than whole milk.

It is also a brilliant detox ingredient; the peppery mustard oils boost and regulate the activity of the liver's enzymes. Watercress is packed with beta-carotene and Vitamin A equivalents, which are great for healthy skin and eyes. It provides iodine and most B vitamins, including folic acid, which is important for a healthy pregnancy.

Watercress is naturally low in calories and fat. Apparently, Liz Hurley drinks up to six cups of watercress soup a day when she's on one of her famous diets.

Watercress rings all sorts of bells for me. One of my earliest memories was of picking tender young watercress leaves with Mrs Lalor in the Chapel Meadows near Cullohill, Co Laois. When we came home we made salad, using it instead of lettuce to accompany the predictable tomato, hard-boiled eggs and scallions liberally doused with salad cream – a flavour sensation I still love to this day.

When I arrived at Ballymaloe many years later, again we picked watercress and used it to make robust watercress soups and dainty little 'butterfly sandwiches' with thinly sliced white bread. Watercress grows wild in rivers and streams all over the country, but it has to be emphasised that one needs to be extremely careful where one picks it. The water must be clean, unpolluted and constantly flowing. Check that there are no animals, particularly sheep, directly upstream, or it's possible that it may harbour liver fluke. This is not to be taken lightly: it's a very nasty and tenacious disease. However, there are some clean streams where one can pick beautiful fresh sprigs of watercress.

For the uninitiated, watercress grows side by side with wild celery, a plant which looks remarkably similar. So how can one distinguish one from the other? The top leaf is always the biggest on watercress and the leaves get smaller as they go down along the stem. The leaf pattern is the opposite on wild celery. Older people always spoke about watercress in the same reverential tone that they used for nettles, the other wild green which 'purifies the blood and keeps away the rheumatics for a year', according to ancient lore. What makes watercress unique is its high levels of a compound called phenylethl isothiocyanate, or PEITC. This gives the plant its unique peppery flavour and in scientific studies has been shown to increase the body's potential to resist certain carcinogenic (cancer causing) agents.

Watercress is a classic ingredient in salads and sandwiches and of course it makes a delicious soup. Here are 12 suggestions for ways to use this classic little salad leaf.