Watercress

Good for horses!:
http://holistichorse.com/equine-therapy/herbs/474-combat-cancer-with-watercress
Good for you!:
http://www.dailymail.co.uk/health/article-436358/Daily-bunch-watercress-cut-cancer-risk.html
Grow it at home!:
http://www.clarkarty.com/at-home/how-to-grow-watercress-at-home/
Most seems to be grown in the UK:
http://www.thewatercresscompany.co.uk/process.php
What is this? Is it for real? Is it safe to buy chemicals from China?:
http://www.ebiochem.com/product/watercress-extract-powder-5-1-13702
The Government says so! It must be true!:
http://www.ncbi.nlm.nih.gov/pubmed/21442676
This supplier is in the U.S.:
http://www.21food.com/products/watercress-powder,-extract,-concentrate-749858.html
http://www.npnutra.com/