Not in a container but here is my experience growing watercress in the garden, Star Stuff: The neighbor has a 4" irrigation pipe along the fence line. A few years ago, his main irrigation valve had a leak and the water traveled about 100 yard were it leaked out of the irrigation pipe along the fence line. It was actually leaking thru several years. I talked to him about how I was going to take advantage of that: put in a 2" pvc pipe and ran that slowly leaking water to a little pool in my garden about 6 feet away from the fence. The pool was about 2' by 4' and 6" deep. The soil here is very rocky so drainage isn't a problem. I just replaced some of the top soil in the bottom of the pool after I'd dug down about 10". A trip to the grocery store provided me with the watercress starts. I remember that the pool ran dry once or twice for half a day or so. That didn't seem to make any difference to the plants. They were lush and beautiful. The next year, the neighbor replaced his irrigation valve and my little pool was filled in and went back to being a bed in the garden. I think I embarrassed him . . . digitSteve

"But with plants in the dirt, do I simply rinse the dirt from their roots & place them in the grate in the top of the filter with their roots in the water?" Karen, for your purposes it is best to plant aquatic plants in mesh containers with gravel to weigh and anchor them down. No need to plant in dirt as that will just cloud the water with the brisk flow through the bio-filter. Place the mesh containers with the plant and gravel atop the filter media and grate. If it's like my Atlantic filterfalls, the top of the mesh pots (containers are about 4" to 5" tall) are just about even with the water line. The gravel and mesh also allows the roots to continue to extend into the filter area. You can either cut them back every so often or just let them grow and grow... however, they can tangle-up filter media pretty good.

Pfaf.org... " sow spring in a pot emmersed to half its depth in water. Germination should take place within a couple of weeks. Prick out seedlings into individual pots whilst they are still small and increase the depth of water gradually until they are submerged. Plant out into water in the summer. Cuttings can be taken at any time in the growing season" If doing this indoors, you may want to change the water in the holding container from time to time. And provide a fan periodically for air movement...but that's thinking out loud, I haven't grown watercress.

Hi brodpro. The short answer is toss the pot along with the potting soil and get the watercress into the water where it will root & multiply and function as a filter. Watercress can be persnickety but it's easy to grow given the right conditions. It does best in cool temp moving water so a stream is ideal. I just tuck sprigs under rocks where water is flowing & leave it alone. It dies back in the intense summer heat here but reappears when cooler weather approaches and is back every spring. Btw, I buy mine in the produce dept of the grocery store for a buck & some change. It will root almost overnight once in the pond. I also toss a few sprigs in my skippy & it is totally obscured in short order. It fares better there as the skippy is shaded during the heat of the summer. No room for a floating island in my pond (actually three puddles that flow together) so I had to get creative. I took one of those rectangular foam pads meant for kneeling in the garden, drilled it full of holes & slipped a sprig of watercress in each hole. I anchored my tiny makeshift island at the base of my waterfall (a delusion of grandeur, more like a cascade). The foam kneepad was soon hidden by the watercress. Been doing this for years with excellent results. Can't beat a successful project for under $3 On the other hand, water hyacinth flat out refuses to perform for me yet I stubbornly continue to buy it year after year. It will live - and bloom even! - but it will.not.multiply. Makes me crazy to see ponders here tossing it by the bucket load on the compost pile. Good luck with your watercress. It's mid-spring for you isn't it? blessings, ~digger