Adiantum formosum

Giant Maidenhair Fern, Black Stem Maidenhair

Family: Pteridaceae

A perennial ground fern growing to about 120 cm.

Widespread, growing in colonies in rainforest or open forest, on alluvial flats near streams, along the coast to the ranges from QLD, down into Victoria. It can dominate the groundlayer in some cases (eg: along the southern end of Lady Carrington Drive in the Royal National Park).

Dark green fronds 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.

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

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.

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

Not overly common in cultivation but would likely do well.


Other information

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

Can regenerate from rhizomes after fire.

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: vulnerable) in Victoria but not considered at risk in the wild elsewhere.


By Jeff Howes