April in the hills with Chris Horne
Pyrrosia eleagnifolia, Ota, Leather-leaf fern
Pyrrosia, derived from the Greek word for ‘flame-coloured’, refers to the fawn-coloured hairs on the undersides of the fronds of this endemic fern – eleagnifolia, also of Greek origin, means ‘with leaves like the olive tree’.
Distribution and habitat
Leather-leaf fern grows on the North and South islands, and on the Kermadec, Three Kings, Rakiura/Stewart and Rekohu/Chatham islands. This tough, adaptable fern can survive in very dry conditions. It is common throughout the country, ranging from exposed coastal areas to montane forests. Look for it growing on the ground, climbing over rocks, or as an epiphyte on native and introduced trees.
Ota’s rhizome, 1-2 mm in diameter, is long-creeping, branching and scaly.
Ota’s appearance differs markedly from that of many other ferns. The thick, fleshy, leathery, blunt-ended, tongue-like fronds are leaf-like, dark green, with scattered hairs on top, and dense, fawn-coloured hairs underneath. The thickness of the fronds and their hairy undersides make them drought-resistant. Their shape is extremely variable, and their margins are smooth. They are attached to the rhizome by winged stipes/stalks up to 2 cm long. The fronds have two forms:
- fertile – elongated, 4-12 cm long x 1-2 cm wide;
- sterile – shorter, egg-shaped, or almost round, up to 7 cm long x 2 cm wide.
The fertile fronds bear dome-like, round or oval sori on their undersides in two or more rows either side of the midrib and away from the margins. When the sori ripen and open, they release the yellow spores, which are spread by the wind to germinate on the ground, on rocks, or on tree trunks.
Other than providing an eye-catching subject for your photographs, there are no recorded uses for ota in either pre- or post-European times.
Where to look for ota
Keep an eye out for this common fern wherever you go tramping, up to c.1000 m above sea level. A fine specimen of it is growing on a large ngaio* on the berm outside 106 Upland Road, Kelburn. With its rhizome clinging to the bark, ota almost surrounds the trunk and climbs all four main limbs to a height of c. 5 m above the ground. This example is one of several you can see on Upland Road, some on native trees, others on exotic trees.