Adiantum formosum

Giant Maidenhair Fern, Black Stem Maidenhair

Family: Pteridaceae

A perennial ground fern with erect fronds, growing to about 120 cm tall.

It has a widespread natural occurrence, growing along the entirety of the coastal subdivisions of NSW into the Blue Mountains and parts of the Hunter Valley, extending into Queensland, mostly to Gladstone but with disjunct occurrences around Mackay. It also extends disjunctly west into Carnarvon National Park. It grows in the north-east of Victoria only, between Orbost and north-east to the border. It also grows in New Zealand on the north island.

It is often grows in colonies, in rainforest or wet-sclerophyll forest, as well as on alluvial flats near streams, usually on enriched soils. It can dominate the groundlayer in some cases (eg: along the southern end of Lady Carrington Drive in the Royal National Park).

Adiantum spp. can present with a variety of frond-appearances. In this species, dark green fronds with very dark stalks / stipes grow to 1.2 m tall, stemming off long-creeping rhizomes that are deeply buried sometimes to a depth to 60 cm. The fronds have a very attractive appearance with the frond foliage about 60 cm or more long by 50 cm wide. Each frond is considered compound-pinnate with the foliage divided twice or more into lobed segments, to 15 mm long, ranging from mid to dark green.
This contrasts strongly with the stipes (frond stalks) which are black and shiny and rough to touch. The minor parts where the frond-segments attach can have reddish-hairs.

Being a fern, no flowers or fruits are produced. Rather, spores are produced.

Spores are produced in sporangia, which are housed in a sorus (plural sori). The sori are produced on the underside of frond segments and follow the segment edges.

In the garden

This species is not overly common in cultivation but would likely do well.

Grows best in acidic, well-drained soil and requires plenty of water and high humidity to grow at its best. It is a very attractive and vigorous fern that is tough and hardy provided it has enough moisture.

It can make a dense groundcover over many metres. Fronds can die off over time. These can be cut back to encourage new growth. Grow in dappled shade for best results. May also work well in a pot.

Susceptible to leaf burn in low humidity or when soil dries out.


Propagation is from plant division (rhizomes) or by spores.

Other information

Can regenerate from rhizomes after fire and can be observed to thrive in some areas after fire.

Adiantum is a genus of around 200 species – cosmopolitan in distribution. Australia reportedly has around 8 species, found in all states and territories. NSW currently has 7 species.

Adiantum – from the Greek adianton (ἀδίαντον) meaning “not wetting” or “un-wet-table, referring to the fronds’ ability to shed water without becoming wet, likely due to the waxy surface of the segments.

formosum – is the Latin word for “handsome” or “beautiful” in reference to the fronds.

Listed as threatened (category: critically endangered) in Victoria but not considered at risk of extinction in the wild elsewhere.

NSW Flora Online (PlantNET) – Adiantum formosum profile page    https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Adiantum~formosum

VICFlora – Flora of Victoria Online – Adiantum formosum profile page https://vicflora.rbg.vic.gov.au/flora/taxon/8248f208-5b0f-4a1e-8f10-95c8584a90f9

Wikipedia – Adiantum formosum profile page https://en.wikipedia.org/wiki/Adiantum_formosum

By Jeff Howes. Editing and additional text by Dan Clarke