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 don’t need a river or stream running through your garden to grow watercress. You don’t even need a garden to grow it - a large pot and a shady spot is all you’ll 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.
Don’t 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, don’t 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.
Kris Collins works as Thompson & Morgan’s communications officer, making sure customers new and old are kept up to date on the latest plant developments and company news via a wide range of media sources. He trained in London’s Royal Parks and has spent more than a decade writing for UK gardening publications before joining the team at Thompson & Morgan.