How do you grow water cress in a pond?
Growing Watert Cress
Certified GKH Gardening Expert
These will usually need moving water to grow properly. Sitting water such as in ponds will not likely let them flourish. There are still ways to grow this, so you might think about doing so in container. This article will help: https://www.gardeningknowhow.com/edible/herbs/watercress/growing-watercress-in-gardens.htm