People have recognised the health benefits of watercress for centuries. Although the story that Hippocrates set up his first hospital by a spring in 400BC so armfuls could be grown to feed patients is probably false, it’s taken modern medicine a little while to catch up to the benefits of watercress. Eaten raw it releases mustard oils which cause it’s peppiness. These oils, similar to brassicas are antioxidant and may slow the growth of certain cancers. It is also high in vitamin C and other vitamins and minerals.
To grow your own watercress firstly buy a large properly with a pure chalk spring free from impurities, follow generations of farmers gently tending their watercress beds donning your waders to harvest as this photograph from Harpenden history shows
Chalk beds, Spring fed or bore fed watercress beds were traditionally always used as a guarantee of purity, free from pollutants, especially free from a liver fluke which comes from fish, mud snails, cattle or sheet that can infect humans. This fluke makes watercress eaten raw from sources, where hygiene standards have not been maintained a health risk. Therefore if you do decided to forage for watercress then cooking is advised.
Alternatively you can grow your own with no need for a stream. Watercress needs to be kept moist but it does not need flowing water. You can mimic it’s conditions at home with little more than a pot and a waterproof dish.
You can either grow watercress as a short term micro greens or let it grow on to become a cut and cut again salad. Micro greens have a higher initial nutritional value and more tender shoots but much less yield. Watercress is perennial so as long as you look after it well, you should be able to crop from it year after year. The initial process is the same for both.
n spring mix a compost (John Innes Number 3 or similar for potted plants) with a little water retaining granules (according to granules instructions) and place in a dish of water. Top up until the compost is saturated. Sprinkle the surface of the compost thinly with the watercress seeds, press down lightly but do not cover. For micro greens sow much more thickly. Keep above 8 degrees, ensuring that the water is topped up if needed and germination should happen in just over a week.
If growing micro greens you would harvest now
Photo from greencityinitiative
If growing your watercress on, place in a lightly shaded position that is above 8 degrees until the first true leaves are showing. In a trug, pot or trough with a waterproof tray plant up the watercress, again using John Innes Number 3 and some water retaining granules allowing 10 cm per plant or 3 plants per a 30 cm pot. Water well. Plants can be moved outside in late spring, with a one week hardening off period when you take the plants outside during the day and bring back in at night. Never let your watercress dry out. Pick often to ensure tender stems and prevent flowering. You should be able to harvest watercress until November/December when production will slow down. You can grow a later sowing under cover for cropping through the winter, although yields will be less.
In the Kitchen
Watercress can be used raw in salads, sandwiches or smoothies. It is advisable to remove or chop any large stalks first as these can be tough. Watercress can also be used in soups, risotto, pasta fillings or where ever you would use spinach. Cooking negates it’s health giving antioxidants. Even if cooked though it will still be high in vitamins and minerals.
Yield and plant health
Unless you have a watercress bed you are unlikely to keep a family supplied with watercress if you eat it often however it is a fun addition to your growing. Keep the watercress well watered and protected from the worst of the frost and you should be able to get a salad bag per plant per year.
Watercress can suffer from both slugs and aphids. If your tray of water is big enough and constantly topped up slugs should not be a problem as they cannot swim! Aphids are more likely to be a problem if kept indoors. Wash the leaves gently to remove the aphids.