The Hard Water Fern is in Family Blechnaceae.
It is endemic to eastern Australia.
A terrestrial, occasionally epiphytic, fern with a branched, creeping rhizome with dark scales.
Young fronds have pink to red leaflets.
Fronds are erect to almost so and usually from 30 to 70 cm long but can be twice that.
The stalks are long and have brown scales.
The lamina is pinnate with up to 17 pairs of leaflets on short stalks.
The leathery leaflets are dark green above, paler below and have finely toothed margins.
The sterile and fertile fronds are different.
Sterile segments are 16-18 cm long and oblong to lanceolate.
The lower segments have a short stalk but the terminal ones have none.
Sterile fronds are sometimes incompletely divided (pinnatisect rather than pinnate).
The central vein is prominent.
Fertile fronds are slightly shorter with narrower linear segments.
The leaflets have 3 longitudinal veins with an extra one on either side of the midrib.
Frond stalks are up to 65 cm long, dark purplish at the base, pale brown above and scaly.
The midribs are pale to pinkish-brown and scaly.
The sporangia are grouped along the 2 lateral central veins.