Many plants used in aquariums can be grown submersed or emmersed. The Planted Tank forum is a fantastic resource for lighting, plant info, etc. here is a link to the riparium, terrarium sub forum. I am sure there are people there that can help. One thought I have is, could you put the plants in very small pots, then sink them into the peat?
http://www.plantedtank.net/for...
