Blechnum tabulare has underground stems (rhizomes) which are erect, occasionally spreading and frequently massive. Rhizome scales are profuse, brown with a blackish-brown central stripe. They are 15 - 50 mm long. The leaves, known as fronds, are arranged in whorls, and may be rigid. The leaf stalk is up to 300 mm long and glabrous; except for tufts of scales at the base, which are similar to those found on the rhizome. This plant consists of sterile and fertile leaves. The sterile leaves are up to 1.4 x 0.35 m long. Leaves are elliptic to oblanceolate in outline with the base comprising a series of much reduced leaflets. The leaflet bases are sessile. The margins of leaflets are entire. The texture is thickly leathery. The upper surface is glabrous with the undersurface sub-glabrous with the pale-brown hair-like scales set along the leaf margin. There is considerable variation within Blechnum tabulare, seemingly according to the geographical distribution. 

• The plants from the winter-rainfall regions have a large stem and could be classified as mini-tree ferns; and the leaves are more lax or arching. 
• The plants from the summer-rainfall areas seldom have a stem higher than 200 mm and, if they do, it is horizontal; the leaves are held more erect, and the leaflets are commonly tapering. 

The degree of scales on the underside of the leaflet also varies from north to south.