Adiantum


Adiantum, the maidenhair fern, is a genus of about 250 species of ferns in the Vittarioideae subfamily of the family Pteridaceae, though some researchers place it in its own family, Adiantaceae. The genus name comes from Greek, meaning "unwetted", referring to the fronds' ability to shed water without becoming wet.

Description

They are distinctive in appearance, with dark, often black stipes and rachises, and bright green, often delicately cut leaf tissue. The sori are borne submarginally, and are covered by reflexed flaps of leaf tissue which resemble indusia. Dimorphism between sterile and fertile fronds is generally subtle.
They generally prefer humus-rich, moist, well-drained sites, ranging from bottomland soils to vertical rock walls. Many species are especially known for growing on rock walls around waterfalls and water seepage areas.
The highest species diversity is in the Andes. Fairly high diversity also occurs in eastern Asia, with nearly 40 species in China.
Species native to North America include A. pedatum and the closely related A. aleuticum, which are distinctive in having a bifurcating frond that radiates pinnae on one side only. The cosmopolitan A. capillus-veneris has a native distribution that extends into the eastern continent. A. jordanii is native to the west coast.
There is a rich Adiantum flora in New Zealand with 3 endemic species in a total of 10 recorded species. Many of these are common especially in the west and south of the islands.

Cladistics

It is now known that this genus is paraphyletic, and that the vittarioid ferns are derived from this larger paraphyletic genus. However, if Adiantum raddianum, and possibly a few other species, are removed, the remaining plants are then monophyletic.

Cultivation

Many species are grown in the horticultural trade, including all three of the species mentioned, as well as a number of tropical species, including A. raddianum and A. peruvianum. Both A. pedatum and A. aleuticum are hardy to zone 3, and are by far the most cold-hardy members of the genus. A. venustum is also cold-hardy to zone 5. A. capillus-veneris is hardy to zone 7.

List of species