‘Soft Tree Fern’
Botanical Information and Overview
There are two common Maori names for this beautiful New Zealand tree fern Katote or Whe. Cyathea smithii is commonly known as the soft tree fern.
The tree fern was named after botanist John Smith (1798-1888) who presided over the transition of Kew Gardens from private Royal Gardens to national Botanic Gardens.
Cyathea smithii natural distribution includes species natural distribution covers North Island, South Island, Stewart Island, Auckland Islands, and the Chatham Islands. The soft tree fern can be found growing from sea level to 600m (2000ft), in damp lowland and montane forest throughout both the North and South Islands. The species is the dominant tree fern in the cooler forests of higher altitude. Cyathea smithii can be found growing on the Auckland Islands giving it the distinction of being the world’s southern most distributed tree fern.
Cyathea smithii is abundant in the cool damp forests around the Fox and Franz Joseph glaciers in the Westland Tai Poutini National Park where the fern can be found growing right up to the snow line.
Cyathea smithii grows in regions that can see overnight temperatures drop to -4°C (25°F) and occasionally further. Therefore mature specimens can take an ‘overnight’ or ‘radiation’ frosts but would struggle to survive prolonged freezing temperatures.
The Katote is a beautiful and distinctive fern which can grow to 8m (66ft). The brown trunk grows up to 23cm in diameter and is noticeable for retaining only the midribs of dead fronds just below the crown. This skirt of fronds provides additional insulation from winter chills whilst helping to retain moisture around the crown in the hotter summer months. An easy way to distinguish between Cyathea smithii and Dicksonia fibrosa is by looking closely at the skirt. With Cyathea smithii only the midrib of spent fronds remain, with Dicksonia fibrosa often the dried remains of the entire frond remain. This is due to the texture of the fronds, Cyathea smithii has very soft fronds which decompose relatively quickly, with Dicksonia fribrosa the opposite the course fronds do not breakdown so quickly. This often means the skirt on Dicksonia fibrosa is far more pronounced or ‘bushy’.
The soft green fronds grow up to 3m (10ft) long and 0.5m (1.5ft) wide. When new fronds emerge they uncurl in an unusual manner with ‘frondlets’ emerging all at once rather than as the new frond uncurls. Younger plants are noticeable for the abundance of light brown hairs around the stipes or bases of fronds. During colder winters the fern can shed all its fronds, therefore this species is not truly evergreen.
Don’t be lulled into a false sense of security just because the species can tolerate a few degrees of frost Cyathea smithii ideally requires a position that is protected from anything more than dappled sunlight and free from wind. A cool, damp and still position is ideal. Only mature specimens can tolerate harsher conditions. The soft tree fern requires a moist well drained humus soil with lots of organic matter and high in nitrogen.
Family Name: Cyatheaceae
Common Name: Soft Tree Fern
Position: Sheltered position protected from cold winds and direct sunlight
Soil: Moist, humus-rich, well drained, neutral soil.
Growth Rate: medium-fast
Eventual spread: 6m.
Max Height: 8m (less cultivated).
Hardiness: Hardy – will tolerate overnight frosts down to -4°C.