A few days ago we bought a punnet of growing Watercress from a local supermarket. It was very reasonably priced (£1), and provided us with a decent amount of salad material. We are not normally very impressed with the thin weedy stems found in those ready-cut bags of Watercress that are so often the only option; we prefer the big sturdy stalks you can sometimes buy in our Farmers' Markets. This living Watercress seemed like a reasonable compromise. Furthermore, I saw its future potential...
With the punnet of cress nearly finished, I commandeered it to make my own Watercress bed. Many people think that Watercress has to have running water to grow in. Not true. Yes, it will grow better in running water (e.g. the chalk streams of the Meon Valley in Hampshire), but it can manage OK in still water or very wet soil, as long as you top up or change the water fairly frequently.
This is how I made my Watercress bed.
First, find a suitable (watertight) container. I used this slightly damaged black plastic storage-crate, but I'm sure you could easily find something suitable at your Recycling Centre, or even in a nearby skip!
I half-filled it with large stones. This is basically because I wanted to economise on the amount of soil I was going to use.
I covered the stones with a layer of ordinary garden soil about 4 or 5 inches deep.
I added a copious amount of water, making the soil extremely wet - basically mud.
A sprig of Watercress can be successfully rooted in a jar of water in just a few days, but mine already had a mass of roots, and it was only necessary to simply carve it up into suitable chunks.
My chosen container was quite big, so it was easily able to accommodate five of those "chunks". Planting them was a bit like I imagine planting rice is - just push it into the gloopy mud!
So there you go - I now have an ultra-low-cost Watercress Bed.
I'm hoping the Watercress will soon spread out and take over the whole of that container, allowing us to have our own source of fresh cress just outside the back door. I'll let you know how it goes...