On Apr 2, 9:54*pm, houndsy wrote:
Is it possible to grow watercress in the soil, or is running water
required? I'm in London. 6 inches of nice friable soil, then solid clay.
Can I use the watercress that I would buy at the supermarket?

The plant does not require running water: growing it in pots is not
unknown. It does require water.

The requirement for running water is to prevent the transmission of
liver fluke, whose cysts can be attached to the leaves in still water,
contaminated by animal faeces. There is a lot of conflicting advice
about what is safe. I don't know, so I just buy it commercially.