How do you actually sow watercress seeds along running water bank?
PlNting Watercress Along Stream Bank.
Watercress, Nasturtium officinale is invasive in most of North America. Planting it near a waterway will speed the spread via seed of this invasive. Here is some info on planting stream banks and plant selection. https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_043594.pdf