Guide to Growing Cyathea australis

General Information

The name Cyathea australis derives from:

Cyathea - from the Greek 'kyatheion' meaning little cup, referring to the structure that holds the spores.

australis - means southern, or 'of the southern hemisphere'.

The common name is the 'rough tree fern' as the leaf bases and stipe are covered with short spines.

C. australis is endemic to the Southeast Australia. In the wild it inhabits moist mountain areas in Victoria, New South Wales, and Queensland, C. australis is often found growing in similar territory to Dicksonia antarctica but enjoys sunnier exposed spots. Unlike many Dicksonia species C. australis is deciduous even in warmer climates.

C. australis grows at elevations as high as 4,200ft in Southeast Australia, and for this reason it is considered to be slightly more cold-hardy than Dicksonia antarctica. If it's location in Australia is anything to go by the plant could be cold hardy down to -12˚C (10°F), however it would be advisable to protect this plant the same way as D. antarctica until the plant is well established. (For more information see over wintering)

C. australis is an attractive, reasonably fast-growing tree fern which develops a thick, black trunk growing up to 5.5m x 30cm (18ft x 1ft) and fronds that range in length from 1.2m-3m (4-10ft). However, plants can grow substantially larger in the right conditions. The trunk is often lighter at the top where old fronds leave spiny bases, at the bottom section of the trunk is covered with black roots. Like with many Cyathea, C. australis develops a striking open canopy of light green fronds, the fronds are glossy (plastic looking) on top but matt on the underside. The fronds are broader than those of Dicksonia varieties. This plant makes an exceptional alternative to D. antarctica and D. fibrosa giving your tree fern collection something slightly different.

Planting

C. australis will thrive in more open conditions than Dicksonia varieties, these plants do not need heavy shade, plants will thrive in loose well drained soils with lots of organic matter and plenty of water. Once established this species can still withstand some drying out and can survive in drier conditions, but in hot summer periods the plant should be watered several times a week.

Be advised: Unlike D. antarctica, C. australis should always be sold as a rooted plant with fronds, never buy plants that have been cut off at the top and bottom of the trunk. Without established roots systems and fronds C. australis is are unlikely to survive. It is often worth asking the supplier how long the plants have been in there nursery before buying the plant, as plants are often brought straight into the country as bare root balls, potted up and sold. Consequently the plant may survive the first summer and then die over the winter due to a lack of food being stored over the growing period. To reduce the likely hood of this happening buy plants that have been over wintered in the UK, this will insure they have undergone a period of recovery. It is also worth taking extra precautions during the first winter in your care

Prior to planting your specimen, keep it well watered this will help to stimulate the plants roots system allowing the root system to establish faster in its 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 C. australis 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.

Maintenance

The most important maintenance of your C. australis is regular watering. At sizes less than 1ft this should be several times a week and daily for the first summer to ensure a good root system 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.

Over Wintering

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.

Botanical Information and Overview

Family Name: Cyatheaceae

Genus: Cyathea

Species: australis

Position: Partial shade.

Soil: Humus-rich, neutral to acid soil.

Growth Rate: Medium-Fast.

Eventual spread: 3.5m.

Max Height: 5m (less cultivated).

Hardiness: Half Hardy - hardy down to -8˚C with foliage damaged at -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.

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