February in the hills with Chris Horne
Microsorum pustulatum subsp. pustulatum, Kōwaowao, Hound’s tongue
Microsorum means ‘with little sori’; pustulatum means ‘raised blisters’, referring to the lumps on the upper side of the fronds of this fern, which match the clusters of sori below. The repetition of ‘pustulatum’ in the botanical name is to separate it from a closely related species in Australia. You will find the Māori name easy to remember, as a dog’s bark resembles ‘wao wao’. The common name comes from the outline of the juvenile frond.
Distribution and habitat
Kōwaowao is widespread. It ranges from the Kermadec Islands and Three Kings, right down to the Auckland and Antipodes islands, and to Rēkohu/Chatham Islands. It is abundant throughout, except in central Otago. You will often see it creeping on the ground, or over rocks, or epiphytic (growing perched on other plants). It occurs in montane forest, scrub and open areas, usually in drier habitats.
A prominent feature of kōwaowao is its fleshy, far-creeping, branching, often slightly bluish-green rhizome, 4-10 mm in diameter, with blackish-brown scales pressed against it.
The fronds, leathery and very variable in form, are bright glossy-green above, and paler below, with prominent veins. The juvenile fronds have simple, undivided, strap-like blades, narrowly elliptic, 7-25 cm long x 1-3 cm wide.
The adult fronds are 6-45 cm long x 4-30 cm wide. The fronds have up to twelve pairs of pinnae/segments up to 17 cm long x 4 cm wide, with blunt points and smooth or wavy margins, and adnate bases i.e. they are attached to the rachis by their whole width. The fronds are attached to the rhizome by pale brown stipes/stalks 2-25 cm long. This form is described as pinnate, which you can liken to a feather with its filaments either side of the quill.
The underside of fertile fronds bear numerous orange-brown round sori, sunk into the underside of the pinnae/segments, creating bulges on the top side of the frond. The sori are clustered in single rows each side of the main and secondary veins. There may be up to forty sori on each lobe of a frond. When the sori ripen and open, they release the spores, which are spread by the wind to germinate in new sites.
The Te Urewera Tūhoe people cooked the young fronds as a vegetable in hangi/earth ovens. Some Wellington sites Hound’s tongue is common in the city’s reserves. You may spot it covering several square metres of the forest floor, or climbing trees, including the rough trunks of pine trees on the Town Belt. You may also see it scrambling up stone or brick walls.