Ferns and Fern Allies in the Canberra Region
Polystichum proliferum - Mother Shield Fern
Polystichum proliferum is a very hardy ground fern that is widespread on the mountainsides to the west of Canberra. It colonises wide areas both by propagating via proliferous tips at the end of its fronds, and by spores. It is often assoicated with Dicksonia tree fern gullies, growing higher up the slopes, further away from the watercourse than the tree ferns. It grows from a central rhizome, with fronds up to a metre (3') in length. Its fronds are usually a dull darkish green. With age the fern may develop a trunk-like base. To the untutored eye, a large P. proliferum can look like a young tree fern.
There are several varieties of Polystichum
in Australia but it is not at all clear that all species have been fully identified
or described. Polystichum australiense has also be tentatively identified
from the Canberra region.
proliferum is so named because of the proliferous buds it grows on its fronds.
These start as a bud and grow into a small plant, towards the end of the frond,
before the frond sags to the ground and the new plant takes root. The image to
the right shows a young proliferous bud.
One plant we found in the Blue Range, growing under a waterfall (not the usual place for P.proliferum) was distinctly different, both in the shape of the pinnae and the black hair-like scales on the base of the rhachis (stalk). At a distance, too, there was something quite "different" about its appearance, which attracted our attention. Compare this image with the one above to see how the pinnae of the two specimens differ. The photos are of plants collected within a few metres of each other. We intend to look for more specimens of the "new" variety.