Cyathea australis, also known Alsophila australis and commonly known as the Rough Tree Fern in its native of south eastern Australia. Naturally it is found in varied habitats often growing often amongst Dicksonia antarctica on wooded hill and mountain sides in some places as high as 1200 metres above sea level. It can also be found growing in lowland area’s to even coastal locations from shady sheltered positions right through to sunny open conditions showing remarkable adaptability. For us here in the U.K this presents us with possibilities of success with Cyathea australis given it’s relative hardiness and tolerance of more open conditions it may be possible to find a suitable micro-climate in your garden.
Cyathea australis is one species of tree fern that can, with a little care, be grown outside in milder parts of the U.K. Being tolerant of frost down to around minus 7 or 8 degrees celsius for short periods. In the wild Cyathea australis often grows in company of Dicksonia antarctica usually of the fringes where it tolerates more sun and wind than its well known cousin.
If you already grow Dicksonia antarctica and have been bitten by the tree fern bug then the rough tree fern is probably the easiest and most rewarding Cyathea to grow along your Dicksonia with similar demands and almost as hardy. I’d still recommend caution and be prepared to wrap or bring undercover your precious Cyathea during periods of hostile weather but given regular watering/rain and occasional feeding of a dilute seaweed feed during the growing months your fern will reward you with magnificent fronds and majestic stature as it matures.
As with nearly all ferns and tree ferns for optimum growth best located in dappled shade away from strong winds planted in fertile moisture retentive but not waterlogged soil.
Best tip is to incorporate lots of well rotted farmyard manure into your existing soil and if possible add a layer of well rotted humus rich substrate, such as leaf mould or garden compost, as a rich mulch around the base of your fern.
We always recommend some form of winter protection, this very much depends on where you garden and how severe the winter is but always suggest filing or allowing the crown to be protected with a layer of leaves or straw keeping the vulnerable growing point safe and snug from frost.
We like Cyathea australis for its fast growth and general adaptability with fronds rapidly reaching 2 or more metres long even on young plants. As they mature, lengths of up to 4 or more metres are possible.
So to summarise, a rare fast growing, hardyish, very exotic and easy to grow tree fern. Also suitable for container cultivation when young.