I just go to the grocery each spring for mine cost 1.25 per bunch which is all I need for a 4 x 2 foot filter falls. I doubt that the grocery would miss identify watercress.

My original watercress came from the grocery store a decade ago. All of the stores in my area now carry the upland cress but not watercress. Upland cress really doesn't like water very much, so it really doesn't do well in ponds. My problem is the "watercress" from the pond store looks and acts like the upland cress. The two DO look very similar. The watercress I used to have grew like a weed anywhere I put it in the pond. I loved it.

I just purchased some watercress seeds(nasturtium officinale) from Amazon. I am just trying to see if I need to toss the "cress" that is now in my pond. I'm assuming it will be some weeks until my watercress is grown up enough to go into the pond.

Larry, watercress(nasturtium officinale) likes to be grown in a cool situation, and prefers running water to spread it's roots into.
I would suggest you keep the potted seeds in a temperature of no more than 65ºF or in a somewhat shaded area, for the seeds to germinate in ambient temperatures above that.
The pot should sit in a saucer of water to keep the potting soil continually moist, but not soaking.
"Horton"

Dear Horton,
I wanted to clue you in: "it's" means IT IS and never anything else. I am sure you meant "its" in your post when you wrote "spread it's roots."

Wow really???

While upland cress is more "top-growing", watercress has leaf pairs that grow opposing each other continuously up a hollow stem. At each leaf node on either side of the stem is a tiny root hair waiting to sense the presence of water. When it does, it begins to grow and can reach a length of over 10" or 25cm. Dozens of these root hairs can grow from a single watercress stem. Upland cress does not exhibit these root hairs. It is these hairs that make watercress an exceptional aquaponic plant. The cilliated root hairs mechanically filter solids from the water while offering thousands of square inches of surface area to harbor bacteria that consume ammonia to excrete nitrite and a second type that consumes this nitrite to excrete nitrate. This process both removes the ammonia from the fish waste and supplies nitrogen to the watercress to promote growth. We, the benefactors, enjoy both the fish and the watercress... all in a day's work for nature. :-)