Dicksonia antarctica Soft tree-fern

Tree Ferns at Tarra Bulga

There are four main species of tree ferns found in Tarra Bulga National Park, (along with many other fern species) The two most common you will see are Cyathea australis (Rough tree-fern) and Dicksonia antarctica (Soft tree-fern). The Soft Tree-fern is more common in the moister areas including the rainforest gullies while the Rough tree-fern is more dominant on the slopes. Once you get you eye in it is fairly simple to tell the difference between these two, the most obvious being by comparing the trunks. The Rough tree-fern has much of its trunk covered by the remains of broken off stems (Stipes) Which are rough to the touch, while the Smooth tree-fern is soft to the touch and is covered by masses of soft hairs which are actually roots.  On this soft trunk other species of plants will often grow including tree and shrub seedlings, epiphytes and other ferns.

Cyathea australis - Rough tree-fern
Cyathea australis – Rough tree-fern, the broken of scaly frond bases (Stipes) on the upper part of the trunk of these ferns are a quick aid to their identification.

Cyathea australis - Rough tree-fern
Rough trunk of the Cyathea australis – (Rough tree-fern).
Dicksonia antarctica Soft tree-fern
Dicksonia antarctica Soft tree-fern – The trunk is soft to touch around the bases of where the old fronds were attached (stipes)
Dicksonia antarctica Soft tree-fern
Dicksonia antarctica Soft tree-fern, the trunk has a covering of fine matted hairs which are actually roots. In rainforest gullies the trunk is often the host to a range of plant species including epiphytes, tree seedlings and other ferns.

Other key ways to tell the difference between these two common ferns is by feeling the base of the frond stems (known as stipes). The Rough tree-fern is easy to tell once again by running your fingers along the stem and feeling the rough texture.

Cyathea australis - Rough tree-fern
The base of the fronds of Cyathea australis – Rough tree-fern with its rasp like texture.

Another way to tell the difference between these two ferns is to examine the underside of the fronds and search for small yellow discs called Sori (they are groups of sporangia which is where ferns produce and store their spores). The Rough tree-fern has sori in rows closer to the mid-vein of the leaf whilst the Smooth tree ferns are located on the leaf margins and are protected by the edges of the fern leaf curling around them.

Cyathea australis - Rough tree-fern Sori
Cyathea australis – Rough tree-fern Showing the underside of fertile fronds with their arrangement of rows of Sori (Clusters of sporangia where spores are produced).
Dicksonia antarctica Soft tree-fern Sori
Dicksonia antarctica (Soft tree-fern) Showing the underside of fertile fronds with it’s arrangement of Sori (spore producers) on the margins protected by curled up leaf edges.

Another key difference between the two are croziers (which are the coiled up newly developing fern fronds). The Cyathea (or Rough tree-fern) has shiny scales and the Dicksonia (Soft tree-fern) is covered with coarse hairs.

Cyathea australis - Rough tree-fern
Cyathea australis – Rough tree-fern, showing the curled up croziers (new frond buds) recognised by their shiny scales.
Dicksonia antarctica - Soft tree-fern
Dicksonia antarctica – Soft tree-fern Showing the start of a new frond (Crozier) The covering of soft brown hairs are a distinctive feature.

Written by Tarra Bulga

Member of Friends of Tarra Bulga National Park.

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