‘Jade Tree Fern – Wheki Ponga’
The botanical name Dicksonia fibrosa derives from:
Dicksonia – named in honour of James Dickson, 1738-1822, a British nurseryman.
fibrosa – in reference to the fiberous nature of the caudex or trunk.
Native Maori names for this fern include Wheki Ponga and Kuripaka, other common names include the Golden tree fern, the Woolly tree fern, the Jade Green tree fern.
Dicksonia fibrosa is an attractive fern similar to Dicksonia antarctica, although Dicksonia fibrosa is slightly smaller; endemic to New Zealand and has ‘cripser’ foilage. The plants golden brown trunk can grow up to 4.8 x 75cm (16ft x 30in) in height; its fronds are similar to Dicksonia antarctica but are a lighter jade green and are rougher to touch. The fronds grow to a maximum of 1.5 – 2.1m in a spreading canopy of up to 4m (13ft) in diameter. Dicksonia fibrosa is a very slow growing specimen, in cultivation the trunk rarely reaches the maximum figure given. The trunk itself is made up of a central core of very hard woody vascular tissue. This is surrounded by old leaf bases through which root fibres grow, the trunk of Dicksonia fibrosa commonly grows more root fibres than Dicksonia antarctica, this is why the plant is known as the Woolly tree fern.
Dicksonia fibrosa is endemic to New Zealand, growing on both the North and South Islands, Stewart Island and in the Chatham Islands at altitudes of up to 2700ft, it is uncommon to find Dicksonia fibrosa north of the Waikato River and Coromandel Peninsula. In its native habitat the species grow variety of ecosystems from montane forests to lowland forests in the most southern most areas of its range. The species also grows in open or cleared pastureland and can often be found along road sides on the South Island.
In its native habitat Dicksonia fibrosa experiences temperatures as low as -11°C (12°F). For this reason some growers feel that the ‘jade tree fern’ is fully hardy in Britain. However do not be lulled into a false sense of security. Only Mature plants (4ft+) can be left completely unprotected and these may still lose their fronds although they should re-grow healthily in spring. One of the highlights of Dicksonia fibrosa is when the fronds get frosted and die they create a ‘skirt’ around the trunk, protecting the plant from further frosts whilst retaining moisture around the trunk. (For further information see over wintering)
The condition in which Dicksonia fibrosa thrives is in filtered sunlight, loose well drained soils with lots of organic matter and plenty of water. However, this species can still withstand some drying out and can survive in drier conditions. The older the plant the more tolerant it will be to drought. An exposed site will dry plants out more quickly so semi-shade is preferable. Plants in full sun or watered less frequently often result in the development of shorter fronds.
Before planting your specimen, it is recommended that it should be well watered for a few days prior to planting, this will stimulate the plants roots system and allow the root system to develop faster into the new planting position. Dig a hole twice as big as the root ball of the plant and fill with organic mulch. Plant the specimen to the level that it is in its pot, do not cover the trunk as the is an unnecessary. Once the plant is in place keep it damp but do not over water the root ball as this may induce root.
If preferred Dicksonia fibrosa can be grown as a pot specimen. Again, plant as shallow as possible, but remember when picking up the pot that the log will fall out if not held upright. After about 1 year, roots should appear from the bottom of the pot. The plant can then be re-potted into a larger container.
The most important maintenance of your Dicksonia fibrosa is regular watering. At sizes less than 1ft this should be several times a week and daily for the first summer to establish a good root system. Do not spray directly in the ferns crown (top) as in colder weather this may encourage rot. Instead soak the whole trunk, angling the hose from below, the wetter the better.
For plants in containers feeding is necessary after the first year, a small dose of a general purpose fertilizer such a growmore, or fish blood and bone will be adequate. This is less important for plants growing in the ground.
For aesthetic reasons it may be necessary to remove old fronds in the spring, this does not necessarily benefit the plant which subsequently becomes more exposed and susceptible to drying out.
There are three main strategies for providing winter protection to tree ferns: keeping them in a conservatory all year round; overwintering small plants in a protected environment; and protecting larger plants outdoors in situ.
Overwintering smaller plants carefully is important as they are more prone to die if frosts are heavy. Where possible it is advisable where possible to bring any plants 2ft or less into a cool conservatory, greenhouse, or even a shed, where temperatures will be higher. It is also desirable to cover the plant with fleece on those nights with hard frosts for added protection, but remember to water the trunks once or twice a week.
Larger plants, although more hardy, still need some protection. The easiest way to provide this is to is to compact a good amount of straw in the crowns of the ferns to stop ice from freezing the crown. In plants less than 4ft added protection may be necessary by insulating the trunk with polystyrene plants trays belted around the trunk.
Family Name: Dicksoniaceae.
Common Names: Golden tree fern, Woolly tree fern, Jade Green tree fern
Position: Partial to full shade.
Soil: Humus-rich, neutral to acid soil.
Growth Rate: Slow.
Eventual spread: 4.3m.
Max Height: 6m (less cultivated).
Hardiness: Half Hardy – they are hardy down to -8°C and the foliage is hardy to -2°C.
Winter tips: Protect crown from frost by insulating with straw bound chicken wire.
Summer tips: Keep plants moist, water daily during the hotter periods.