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NZ Plants

Blechnum filiforme - thread fern, climbing hard fern

Hard fern family: Blechnaceae

Blechnum filiforme is a climbing fern with a distinct creeping juvenile stage. Adults are high-climbers with large, broad sterile and fertile fronds. The leaflets on the fertile fronds are long and thread-like..
An endemic fern of coastal and lowland forest found from the North Island to the north coast of the South Island.

Vegetative characteristics

Fertile frond and sporangia

Plant form: Creeping, climbing rhizome with fronds up to 700 mm long

Frond appearance:  similar size to sterile fronds but with long and very narrow (thread-like) leaflets

Frond stalk, midrib: scales present

Sporangium location: on lower frond surface

Frond shape: narrowly ovate-elliptic

Sporangium position: leaflet margin

Frond blade: pinnate (divided 1 x into leaflets or pinnae)

Sporangium distribution: in groups (sori)

Frond surface: leathery

Sorus shape: in a continuous line either side of midrib

Leaflets: narrowly triangular-ovate, pointed; attached by a basal stalk

Sorus covering: linear covering (indusium) opening toward midrib

Juvenile: 50-250 x 10-50 mm linear fronds with elliptic-oblong , toothed and rounded leaflets