Blechnum orientale L.

Rhizome forming stout erect or suberect caudex, usually short (6-20 cm) but occasionally forming a tree fern up to 2 m, 4-5 or more cm diam., densely covered with linear-narrowly elliptic scales, 1-2(-3.5) cm long usually less than 0.2 cm wide at the base, entire, shiny reddish brown. Fronds: fertile and sterile fronds similar, erect, variable in size but up to and sometimes more than 200 by 54 cm. Stipes very short, 1-9 cm but usually only about 5 cm, and for large fronds up to 2 cm diam., dark purplish, with persistent narrow, acuminate scales tapering to a fine wavy and often twisted apex, mostly entire, brown to reddish brown, surface of stipe often clothed with very fine tangled pale hairs. Lamina narrowly elliptic to ovate, pinnate, pinnae dense on the rhachis, 6-70 or more pairs of pinnae (not including auricles), pairs subopposite to alternate usually 2.5-5 cm apart and 0.2-0.3 cm in length and width but the lowermost often less than 0.1 by 0.1 cm. Rhachis and costae pale pinkish brown, paler on grooved adaxial surface, glabrous or with sparse irregular hairs and slender reddish brown scales. Sterile pinnae narrowly elliptic, the apices gradually and evenly tapering to their tips, 5-30 by 0.5-2 cm, increasingly adnate and markedly basiscopically decurrent towards apex, and tending to become truncate or cuneate and sessile to subpetiolate or petiolate towards the lamina base, fresh material very variable in texture but usually coriaceous, margins entire and sometimes revolute (especially in exposed situations), gradually reducing to small rounded leafy auricles towards base, and reducing towards the frond apex, veins very fine immersed simple or forked once sometimes twice, often less than 0.5 mm apart. In juvenile plants the pinnae are fully adnate, those towards the apex are markedly decurrent while those towards the base have rounded obtuse apices and minute auricles extend down the rhachis to the stipe. Fertile pinnae similar to sterile pinnae except for presence of narrow sori (0.1-0.2 cm) closely parallel to and on either side of the abaxial costa; sori at maturity may obscure the abaxial surface of the costa. Spores 46.7 by 36.9 µm (from 13 herbarium specimens), perine with irregular ridges, loosely reticulate, rugulose or scabrous, exine smooth to scabrous.

Grows in a range of habitats, from dry exposed soil banks (where the plants are small) to creek banks, waterfalls, seepage areas, swamps, and open spaces on the margins of lowland and sometimes upland tropical and subtropical forests (where the plants may be large). A fern of high light conditions and exposed habitats and often a primary coloniser.

Uses “Blechnum orientale L. is used together with Elephantopus scaber [an abundant tropical weed in the Compositae] for dropsy. The fern is believed to entice out the ‘centipede’ [or worm or snake] which has lodged in the liver” ( Johnson Malayan Nat. J. 11 1957 59 ). A recent paper by Christensen (Holttum Mem Vol. (1997)) records the vernacular names pao abu for the Kelabit and kelindang for the Iban people; both groups use the species for medicine and as a vegetable. The Kelabit in Nanga Sumpa pound young fronds and use the resulting paste to treat blisters and abscesses; in Pa Dalih a decoction is made from the young fronds and drunk to treat mouth ulcers. Also in Nanga Sumpa, B. orientale is mixed with hot spices and other vegetables and eaten raw as ulam.

Plants are grown from spores.