Adiantum

Adiantum, the maidenhair fern (not to be confused with the similar-looking maidenhair spleenwort fern), is a genus of about 250 species of ferns in the subfamily Vittarioideae 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 (five-fingered fern) 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 (Venus-hair fern) has a native distribution that extends into the eastern continent. A. jordanii (California Maidenhair) is native to the west coast.

There is a rich Adiantum flora in New Zealand with 3 endemic species (A. cunninghamii, A. viridescens and A. fulvum) in a total of 10 recorded species. Many of these are common especially in the west and south of the islands.

List of species

 * Adiantum abscissum
 * Adiantum aculeolatum—synonym of Adiantum mindanaense
 * Adiantum adiantoides
 * Adiantum aethiopicum – common maidenhair, true maidenhair
 * Adiantum alarconianum
 * Adiantum aleuticum – Aleutian maidenhair, western five-fingered Fern
 * Adiantum amazonicum
 * Adiantum amblyopteridium
 * Adiantum amelianum
 * Adiantum anceps – double edge maidenhair
 * Adiantum aneitense
 * Adiantum angustatum
 * Adiantum annamense
 * Adiantum atroviride
 * Adiantum bellum – Bermuda maidenhair
 * Adiantum bessoniae
 * Adiantum blumenavense
 * Adiantum boliviense
 * Adiantum bonatianum
 * Adiantum bonii
 * Adiantum brasiliense – Brazilian maidenhair
 * Adiantum breviserratum
 * Adiantum calcareum
 * Adiantum capillus-junonis
 * Adiantum capillus-veneris – black maidenhair, southern maidenhair, Venus' hair
 * Adiantum caudatum – walking maidenhair, tailed maidenhair, trailing maidenhair
 * Adiantum celebicum
 * Adiantum chilense
 * Adiantum christii
 * Adiantum comoroense
 * Adiantum concinnum – polished maidenhair, brittle maidenhair
 * Adiantum coreanum – Korean maidenhair fern
 * Adiantum crespianum
 * Adiantum cultratum
 * Adiantum cuneatiforme
 * Adiantum cuneatum (junior synonym of A. raddianum)
 * Adiantum cunninghamii
 * Adiantum cupreum
 * Adiantum curvatum
 * Adiantum davidii
 * Adiantum diaphanum – filmy maidenhair, small maidenhair.
 * Adiantum dioganum
 * Adiantum diphyllum
 * Adiantum discretodenticulatum
 * Adiantum dissimulatum
 * Adiantum edgeworthii
 * Adiantum elegantulum
 * Adiantum erylliae
 * Adiantum erythrochlamys
 * Adiantum excisum – Chilean maidenhair
 * Adiantum fengianum
 * Adiantum fimbriatum
 * Adiantum flabellulatum
 * Adiantum formosum – giant maidenhair, Australian maidenhair
 * Adiantum fossarum
 * Adiantum fragile – fragile maidenhair
 * Adiantum fragrans
 * Adiantum fructosum
 * Adiantum fulvum
 * Adiantum gertrudis
 * Adiantum gibbosum
 * Adiantum gingkoides
 * Adiantum glabrum
 * Adiantum glaureosum
 * Adiantum glaucescens
 * Adiantum glaucinum
 * Adiantum glaziovii
 * Adiantum gomphophyllum
 * Adiantum gracile
 * Adiantum gravesii
 * Adiantum grossum
 * Adiantum hispidulum – rough maidenhair, rosy maidenhair
 * Adiantum hollandiae
 * Adiantum hornei
 * Adiantum hosei
 * Adiantum imbricatum
 * Adiantum incertum
 * Adiantum incisum
 * Adiantum intermedium
 * Adiantum jordanii – California maidenhair
 * Adiantum juxtapositum
 * Adiantum kendalii
 * Adiantum kingii
 * Adiantum klossii
 * Adiantum lamrianum
 * Adiantum latifolium – broadleaf maidenhair
 * Adiantum lenvingei
 * †Adiantum lianxianense
 * Adiantum lindenii
 * Adiantum lonrentzii
 * Adiantum lucidum
 * Adiantum macrocladum
 * Adiantum macrophyllum – largeleaf maidenhair
 * Adiantum madagascariense
 * Adiantum malaliense
 * Adiantum malesianum
 * Adiantum mariesii
 * Adiantum mariposatum
 * Adiantum mcvaughii
 * Adiantum melanoleucum – fragrant maidenhair
 * Adiantum mendoncae
 * Adiantum menglianense
 * Adiantum mettenii
 * Adiantum mindanaense
 * Adiantum monochlamys
 * Adiantum monosorum
 * Adiantum multisorum
 * Adiantum myriosorum
 * Adiantum neoguineense
 * Adiantum novae-caledoniae
 * Adiantum nudum
 * Adiantum oaxacanum
 * Adiantum obliquum – oblique maidenhair
 * Adiantum ogasawarense
 * Adiantum opacum
 * Adiantum ornithopodum
 * Adiantum ovalescens
 * Adiantum palaoense
 * Adiantum papillosum
 * Adiantum paraense
 * Adiantum patens
 * Adiantum pearcei
 * Adiantum pedatum – northern maidenhair, five-fingered fern
 * Adiantum pentadactylon
 * Adiantum peruvianum – silver-dollar fern, Peruvian maidenhair
 * Adiantum petiolatum – stalked maidenhair
 * Adiantum philippense
 * Adiantum phyllitidis
 * Adiantum platyphyllum
 * Adiantum poiretti
 * Adiantum polyphyllum – giant maidenhair
 * Adiantum pseudotinctum
 * Adiantum pulchellum
 * Adiantum pulcherrimum
 * Adiantum pulverulentum – glossy maidenhair
 * Adiantum pumilum
 * Adiantum pyramidale – pyramid maidenhair
 * Adiantum raddianum – delta maidenhair
 * Adiantum rectangulare
 * Adiantum reniforme – lotus-leaved maidenhair fern
 * Adiantum rhizophorum
 * Adiantum robinsonii
 * Adiantum roborowskii
 * Adiantum rondoni
 * Adiantum rubellum
 * Adiantum rufopetalum
 * Adiantum scabrum
 * Adiantum schmalzii
 * Adiantum schmidtchenii
 * Adiantum schweinfurthii
 * Adiantum seemannii – Seeman's maidenhair
 * Adiantum semiorbiculatum
 * Adiantum senae
 * Adiantum serratifolium
 * Adiantum shastense
 * Adiantum siamense
 * Adiantum silvaticum
 * Adiantum sinicum
 * Adiantum soboliferum
 * Adiantum sordidum
 * Adiantum stenochlamys
 * Adiantum stolzii
 * Adiantum subcordatum – big maidenhair
 * Adiantum subpedatum
 * Adiantum tenerum – fan maidenhair, brittle maidenhair
 * Adiantum tenuissimum
 * Adiantum tetragonum
 * Adiantum tetraphyllum – fourleaf maidenhair
 * Adiantum thalictroides
 * Adiantum trapeziforme – diamond maidenhair
 * Adiantum tricholepis – fuzzy maidenhair
 * Adiantum trilobum
 * Adiantum tripteris
 * Adiantum venustum – evergreen maidenhair, Himalayan maidenhair.
 * Adiantum villosissimum
 * Adiantum villosum – woolly maidenhair
 * Adiantum viridescens
 * Adiantum viridimontanum – Green Mountain maidenhair
 * Adiantum vivesii – Puerto Rico maidenhair
 * Adiantum vogelii
 * Adiantum wattii
 * Adiantum wilsonii – Wilson's maidenhair
 * Adiantum zollingeri

Cultivation
Many species are grown in the horticultural trade. There are 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. Hybrids, such as Adiantum × mairisii, are also popular.