I found some marked down discount seeds at a garden store today. love to eat watercress, it’s like an amazing peppery spinach. I tried to grow it once before and failed but now with new knowledge I’m going to try again. Apparently you grow watercress exactly like most carnivorous plants and as a bog plant that makes sense. 1part peat, 1part sand or perlight and tray water sounds fool proof! Wish me luck! https://m.wikihow.com/Grow-Watercress
I grow some in my pond, initially by putting a couple of sprigs in from the supermarket into the pond, just laid in the water at the margins and it grows like a weed, gets very invasive and grows tall, so I would think that it would soon overshadow any plants in your bog and prevent light reaching the plants. The nutrients in the pond water (there are fish in there) obviously agree with the plant as it outcompetes all other plants, I’m not sure how it will do in a nutrient free mix such that you are proposing, I would have thought that any water mix and soil kept in say a bucket would do the job successfully as long as it doesn’t get anaerobic. I have to have a clear out a couple of times a year in the pond but it still comes back and soon inhabits any wet and boggy areas it can get to. Cheers Steve
Since it’s winter right now we are sprouting it with other seeds for salads and sandwiches Also experimentally growing it inside on our fresh spice shelf. Apparently it likes slightly acidic conditions with slow flowing cold water threw the soil much like Darlingtonia. In the spring we will try it in our bathtub pond and also the big pond out back of our place.
There is water cress growing in all the creeks behind me, one thing i think would be important to note is i have never found it in a pond, or still water. Its always along the edges of creeks, sometimes under water sometimes half under water. And it tends to grow in pockets where the creeks swirl and nutrients and substrate build up. Good luck!
