disused watercress beds - what plants ?

We have four watercress beds in use, with organic status, and an
additional four beds adjacent which we do not want to run water
through. They have a shale base and high water table and we are wanting
to find a vegetable / plant / herb that would be suitable for those
conditions and would be saleable . They are in a sunny, sheltered Devon
valley and apart from the odd duck or moorhen,
are undisturbed !
All suggestions welcomed !




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stellacress