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NZ Plants

Blechnum colensoi - peretao, Colenso's hard fern

Hard fern family: Blechnaceae

Blechnum colensoi has a stout, erect stem with dissimilar sterile and fertile fronds (dimorphic).
The elliptic sterile fronds are dark-blue green and leathery, undivided or divided once into a small number of broad leaflets. Fertile fronds are extremely slender with long terminal leaflets.
An endemic fern found in wet lowland to mountain forest from Auckland southwards.

Vegetative characteristics

Fertile frond and sporangia

Plant form: a short, erect trunk with fronds up to 500 mm long

Frond appearance: about as long as sterile, very narrow, with long, narrow leaflets

Frond stalk, midrib: scales

Sporangium location: on lower frond surface

Sterile frond shape: elliptic to rhomboid

Sporangium position: leaflet margin

Frond blade: undivided or 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: oblong, smooth margins and a tapering, pointed tip; attached along leaflet base (adnate)

Sorus covering: linear, opening toward midrib