I grow D. intermedia and D. filiformis and tracii var. outside all
year here in northern NJ. They are in 90% peatmoss top dressed with 1/4
in. layer of sand. I saw filiformis growing wild in near 100% sand
along the edge of a pond in the Pine Barrens. I keep them very wet and
they receive full sun 2/3 of any given day. I had trouble growing them
indoors. But when moved out they improved dramatically. D.
rotundafolia and D. anglica grow well the same conditions.
Dave Evans