I have gathered quite a few plants from some of the many local lakes & ponds. They were growing in the shallow edges, in sand. The (pond) water tested at 6.8PH, 15GH.
Hornwort is happy in an unheated(72F) tank with about 3/4WPG and also a tank at 76F, with almost 5WPG. The higher light tank also has a ludwigia species (I think) that was alot more red & had rounder leaves in the pond. Also found hairgrass which is doing well emersed in my paludarium. Had a couple others but they melted.