Blechnum australe has bright to dark green fronds, made up of short broad pinnae attached alternately to the rachis. The plant grows from thin creeping rhizomes that emerge above ground from erect parts of the rhizomes in tufts of fronds. The fronds of ferns belonging to this genus are dimorphic, i.e. sterile and fertile ones have different shapes. The fertile fronds with viable spores on the lower pinnae surfaces, from which the plants are propagated, are taller than the sterile ones in this species. Pinnae end in short sharp tips (are mucronate).
B. australe grows in semi-shade among rocks, often close to water. The distribution area is huge, ranging from South Africa to East Africa and some Indian Ocean islands, including Madagascar. It does survive in drier spots, usually at reduced size. The plant resembles the deer fern, B. spicant, a popular species indigenous to England (www.zimbabweflora.co.zw; www.fancyfronds.com).