Cyathea smithii Hook.f.

Rhizomes erect, forming a woody trunk up to c. 8 m tall, 120–320 mm in diameter, covered in dark brown appressed stipe bases; bearing scales near the apex. Rhizome scales marginate, acicular, lacking dark-coloured setae, dark brown, shining. Fronds 1650–3000 mm long, held horizontally; midribs of dead fronds persistent as a skirt around trunk. Stipes 80–450 mm long, 15–30 mm wide and 10–20 mm deep at the base, dark brown proximally, becoming chestnut or yellow-brown distally, weakly tuberculate and slightly rough, bearing hairs and scales; hairs fine, acicular, colourless or pale brown, up to 1 mm long; scales densely covering base of stipe, acicular, dark brown or chestnut-brown, shining, up to 60 mm long and 3 mm wide, becoming narrowly ovate, pale brown, and more scattered distally, interspersed with dense red acaroid scales c. 0.1 mm in diameter. Laminae 2-pinnate-pinnatisect to 3-pinnate-pinnatifid, ovate or elliptic or obovate, 1000–2000 mm long, 450–750 mm wide, dark green on adaxial surface, pale green on abaxial surface, herbaceous; adaxial surfaces of rachis and costae of primary pinnae abundantly covered in fine, acicular, colourless or pale brown hairs up to 1 mm long, becoming scattered on costae of secondary pinnae; abaxial surfaces bearing very scattered colourless acicular hairs, narrowly ovate or acicular pale brown scales lacking dark setae and up to 3 mm long and 0.5 mm wide, and colourless scales with ciliate margins or red acaroid scales c. 0.1 mm in diameter; rachis chestnut-brown, becoming yellow-brown distally. Primary pinnae in 20–30 pairs, narrowly ovate or narrowly triangular; the longest at or above the middle, 230–500 mm long, 60–130 mm wide, short-stalked, reducing proximally to a basal pair less than half the length of the longest pair. Secondary pinnae narrowly ovate or narrowly triangular, the longest 30–65 mm long, 7–16 mm wide, sessile. Longest tertiary pinnae 4–9 mm long, 1.5–2.5 mm wide, adnate or decurrent; apices acute; margins serrate or divided up to halfway to the costa. Sori 0.5–0.9 mm in diameter; paraphyses shorter than sporangia; indusia open on side away from costa before maturity, saucer-shaped at maturity and forming less than a hemisphere, not splitting with age.

Cyathea smithii is readily recognised in the field by its persistent dead stipes and rachises with abraded pinnae, which appear like a grass skirt around the trunk. The only other mainland New Zealand tree fern that regularly forms a skirt is Dicksonia fibrosa, where entire dead fronds are retained. Young immature plants of C. smithii are sometimes confused with C. colensoi, but fertile fronds are only produced on C. smithii when plants have developed trunks more than 1 m tall and can no longer be mistaken for C. colensoi.

Cyathea smithii can be distinguished from C. cunninghamii by its saucer-shaped, rather than hood-shaped indusia. The pale brown lamina scales are also distinctive in lacking dark setae at the apex (Brownsey 1979), and the acaroid scales never have an expanded pale brown base, as is sometimes the case in C. cunninghamii.

One collection of C. smithii from the Chatham Islands (WELT P021516) has larger pinnae than any mainland collection, with primary pinnae up to 600 mm long and 145 mm wide, secondary pinnae up to 80 mm long and 20 mm wide, and tertiary pinnae up to 14 mm long and 4 mm wide. It is unclear whether plants are generally bigger on the Chatham Islands.

Cyathea smithii is a hardy, subcanopy species which favours colder, wetter conditions, and is the dominant tree at higher altitudes and in the far south of the country. It occurs under podocarp, beech, kānuka and broadleaved forest.

n = 69 (Brownlie 1958).

There are six syntype specimens of Hemitelia stellulata Colenso in WELT (P002506-10, P003307), another at AK (143440), and two at K. Allan (1961, p. 43) lectotypified one of the specimens in WELT (P003307) by describing uniquely the material on the sheet ("a portion of a rachis with 8 pinnae").

Buchanan (1887) recorded a specimen of C. smithii from Dunedin which branched to form several heads.