Cheilanthes species - Rock ferns

There are three species of Cheilanthes recorded in the Canberra region, C. austrotenuifolia, C. sieberi, and C. distans. It is very likely that they hybridise, as there is a continuum of characteristics. The species overlap in their ranges, so identification can be a bit tricky. At the extremes of their ranges, they are easier to distinguish.

C. austrotenuifolia (Rock Fern) is the most elegant of the three species, and in favourable situations (after a period of good rain, and with suitable overcanopy) it is a beautiful lacy ground fern with fronds up to 45 cm (18") long. The adjacent image shows a young specimen growing among rocks.

C. austrotenuifolia grows in a range of habitats, including very dry areas, where its fronds are often stunted and difficult to distinguish from C. sieberi (Narrow Rock Fern). Both are amazingly hardy and grow on open rocky hillsides, often among boulders, but sometimes in clumps in open grassland, subject to frost, wind and direct sun. In its inclination to grow among grass tussocks, it resembles the "tree fern Savannah" ecosystem of New Guinea, though on a micro-scale. This habit is described in Duncan and Isaac's book Ferns and Allied Plants of Victoria, Tasmania and South Australia . The illustration at right shows the habit.

The photograph was taken during a long drought in early winter. The hillside was covered with small clumps of Cheilanthes (probably C. austrotenuifolia, though C. sieberi was present nearby). This mix of grass tussocks and Cheilanthes might be termed "Cheilanthes Savannah".

C. sieberi usually grows in harsh areas, often in the open, and appears to favour poorer soils than C. austrotenuifolia It is reported to be poisonous to stock, though this is not a useful diagnostic tool! Its fronds are usually up to 30 cm (12") in length and usually stand upright. It grows among grasses, often among rocky outcrops. Earlier suggestions that C. sieberi was a habitat form of C. austrotenuifolia have been disproved by research in the 1980s.

The third Cheilanthes species is C. distans, or Bristly Cloak Fern. It is superficially similar to small specimens of C. sieberi, but clearly distinguished by the often thick scales and hairs on the under side of its fronds. These are always visible on the unfurling crosiers, which appear as fluffy white tips on new fronds (see illustration at right). The amount of scales and hairs under the fronds varies considerably, and may reflect hybridisation with C. sieberi. Some specimens show sparse white hairs on the upper surface of the pinnae. C. distans often grows among rocks in very frost-prone areas, where its hairs and scales presumably confer competitive advantage. It resembles superficially a specimen of Woodwardia distans I saw next to a fjord in Norway, years ago, growing in a similar habitat.

It is possible that Cheilanthes lasiophylla also grows in the Canberra region, but this remains to be confirmed.

David Nicholls
July 1998