black tree fern blackt·ree·fern uncommon noun 1. showy tree fern of New Zealand and Australia area having a crown of much-pinnated fronds with whitish undersides Synonymssilver tree fernsago fernblack tree fernCyathea medullaris Related words Broader terms tree fern Parts Cyathea WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
