many of the candlelabra primulas do well as does iris psudocarpus, bog bean, globe flower, lobelia cardinalis like it damp too. larger plants include gunnera and the skunk cabbage. then there are the ligularias for late summer/autumn
depending on how wet there are the hostas also.

hope there are some ideas to get you going. why not join us and then you can tel us more about your garden.