@farmerman,
Speaking of watercress:
I actually visited a watercress farm in the greater Tampa rural hinterlands. (Not that far away from the North American watercress capitol in Oviedo, nr Orlando FL) This farm tour was a surprise. This horse-radishy taste was very enjoyable to me (healthy for the blood as a purifier and alkalizer.)
However, a massive amount of this crop is speedily jet shipped to the UK and European markets. Being a sprout, it's highly perishable. It gets to their shelves within 48 hrs from field-to-shelf. We eat very little as a market. Also the domestic prices are way higher than, let's say, alfalfa sprouts so demand is lower as the US public is basically unaware of it and/or hasn't developed the taste for it in large numbers..