Back in February this year I wrote about my attempts to find the best way to grow watercress (Nasturtium officinale) in a container.
Growing it in a pot submerged in water hadn't worked too well for me so I tried growing it in a large tub of sandy compost with minimal drainage and giving regular waterings of tap water. This has been successful and we've harvested it a lot over the year.
It has grown better when the weather has been cooler though. The leaves are a bit smaller than shop-bought watercress. I'm not sure yet if this is because our yard is shadier than commercial watercress beds or because I've only given it an occasional feed. I'll try and remember to set up a rough trial next year to judge this.
Watercress is a brassica and suffers from a similar range of pests as cabbage. I was accidentally well-prepared for defending the watercress against cabbage white butterfly egg-laying attempts. The orange tub pictured above had been previously used for my Daubenton kale cuttings and I had constructed this frame to fit the tub and covered it in netting. It worked well for the watercress too. (The net really needs to be finer for defence against flea beetle and greenfly but we were fortunate not to get many of these in the backyard this year).
As watercress leaves can be killed by the frost I covered the frame with some polythene today. I think this will keep off all but the very worst of the weather this winter. It the temperature drops extremely low and the plants die they are very easily replaced by cuttings from a bag of shop cress.
Watercress appreciates the minerals in hard tap water. What a splendid excuse not to mend that dripping outdoor tap - just site your watercress pot beneath it! But however it is grown watercress is an excellent backyard perennial vegetable as it doesn't mind shade, grows almost all year and gives you a lot of nutrients from a small space.
N.B. I sell a range of perennial vegetable plants on my website.