Polypodium is a genus of
ferns in the family
Polypodiaceae, subfamily
Polypodioideae, according to the
Pteridophyte Phylogeny Group classification of 2016 (PPG I).[1] The genus is widely distributed throughout the world, with the highest species diversity in the
tropics. The name is derived from
Ancient Greekpoly ("many") + podion ("little foot"), on account of the foot-like appearance of the
rhizome and its branches. They are commonly called polypodies or rockcap ferns, but for many species unique vernacular names exist.
They are
terrestrial or
epiphytic ferns, with a creeping, densely hairy or scaly
rhizome bearing
fronds at intervals along its length. The species differ in size and general appearance and in the character of the fronds, which are evergreen, persisting for 1–2 years, pinnate or pinnatifid (rarely simple entire), and from 10 to 80 cm or more long. The
sori or groups of spore-cases (
sporangia) are borne on the back of the frond; they are globose and naked, not covered with a membrane (indusium).
Polypodies have some use in
herbalism, but are today most important in
horticulture where several species, hybrids, and their
cultivars like Polypodium 'Green Wave' are commonly used as
ornamental plants for shady locations. Polypodium have a bitter-sweet taste and are among the rather few ferns that are used in
cooking; in this case as a spice e.g. for
nougat.
Species
Several of the species form
hybrids with other species in the genus; these may often be distinguished by being sterile, with very small "blind" sori. As of February 2020[update], Checklist of Ferns and Lycophytes of the World accepted the following species and hybrids:[2]
^PPG I (2016). "A community-derived classification for extant lycophytes and ferns". Journal of Systematics and Evolution. 54 (6): 563–603.
doi:10.1111/jse.12229.
S2CID39980610.