What are some good beginner plants for a fern or moss terrarium?
maidenhair ferns, heart fern, small adiantum, button ferns, brake ferns, & selaginalla
Note: Concerns w/ collecting moss from outdoors Wild patches of moss can be very slow to recover from the depredations of collectors. Rather than damaging/destroying the micro-ecosystems these are a part of, it is best to leave them alone.
Further more wild mosses are usually very specific with regards to their habitat. A moss growing on a rock is not going to be happy growing on wood mulch for example. Unless care is made to duplicate their microhabitat, they rarely flourish when brought indoors. Also wild mosses may harbor unwelcomed critters like snails.