Watercress is an old, old vegetable. Roman soldiers probably ate it, and you can too if you give it the conditions it needs to thrive. Watercress is very nutritious, containing a large amount of vitamins K, A, C, and a whole host of B vitamins. It is, along with other Brassicas, suspected to have cancer-fighting properties.
Watercress, though it has been cultivated for thousands of years, is likely not available at your local grocery store. At least not for a reasonable price. It grows commonly as a weed, however, and when I saw a healthy stand of watercress (either Nasturtium microphyllum or Nasturtium officinale, both edible) growing in a ditch I couldn’t help myself and took 5 sprigs home with me.
Watercress grows in rivers, ponds, and streams. It seems to like growing in shallow water where most of the plant can be above the waterline. Though many online sources indicated that watercress really does not like standing water, I’ve seen it growing in enough stagnant ponds to know otherwise. Since I can’t make a stream in my backyard, I decided to go with a more bog-like environment.
I took a large rubbermaid tub I had in storage (#5 plastic, should be a lot safer than other kinds) and filled the bottom half with branches and fallen leaves. I filled the top half with some potting mix I had laying around and filled it with water, so that the waterline was about the same as the soil-line. I didn’t want the waterline to be too high, in order to prevent mosquitoes from breeding.
I put the watercress cuttings in water and they very rapidly grew long roots. I then placed them in the waterlogged soil and waited.
Watercress grows quickly and it soon covered the entire container. Watercress has a sprawling habit, in which top-heavy stems fall over and adventitious roots and eventually new stems develop at each leaf node. This allows watercress to spread extremely rapidly when fragments are displaced to new environments, like my plastic tub. The watercress seems to be absolutely fine in the stagnant water and the only care it needs is adding water and removing cabbage white caterpillars (Pieris species) which seem to enjoy eating the tender leaves.
After 4 months of caterpillar attacks and wild weather, the watercress is greener and more lush than ever. Talk about a plant you can neglect – if it rains, I maybe check on it once per week. When it is baking hot and dry, I keep the water filled and otherwise ignore it.
Watercress is great raw or cooked, and it is very easy to cultivate even in a small space. I think watercress has fabulous potential as a specialty cash crop that can be grown effectively in urban places that are limited in space. It could be grown vertically in a hydroponic system, or in simple low-tech tubs and natural ponds. I look forward to keeping watercress as a regular part of my garden and diet and hope you might consider giving it a try.