The peppery leaves of watercress fetch a premium price when you buy them pre-packed at the supermarket, but you can grow your own fresh leaves at a fraction of the cost.
You dont need a river or stream running through your garden to grow watercress. You dont even need a garden to grow it - a large pot and a shady spot is all youll need for regular harvests of mineral and vitamin-rich leaves through summer.
Growing watercress in containers is a safer option than growing it in water - commercial growers know how to keep the water fresh and bacteria-free, this is much harder to do in a garden situation. As long as your watercress plants are kept well watered they will thrive in a pot of good quality compost. To provide the right growing conditions for watercress, simply set your pots in deep trays or dishes that are kept topped up with water. To prevent any stagnation make sure to flush the pots heavily once or twice a week with fresh water. Mixing charcoal with the compost will also help to keep things fresh.
Dont go chasing hard to find watercress plug plants - growing watercress from seed requires no specialist skills or equipment. Outdoor watercress crops should be sown directly into the pot you wish to grown them during March or April - once average day temperatures reach 8-15°C it will be warm enough to encourage germination within 14 days. There is no need to cover watercress seeds, they will sprout happily simply scattered on the surface of the compost. Further sowings can be made through spring and early summer for a constant supply of fresh leaves.
You can also treat watercress seed as a windowsill microgreen, surface sowing in small seed trays pre-saturated with water. Once growth is underway, keep the trays on saucers of water and harvest watercress microgreens when plants are 5cm (2") high or so.
Top tip: If you have a surplus of fresh leaves through summer, dont let them go to waste. Rabbits and guinea pigs eat watercress and will enjoy this tasty treat whenever you have some to spare. Pet birds may also appreciate the fresh leaves too.