Rhizome shortly creeping up to 20mm in diameter. Fronds closely packed; stipe up to 55cm long; sterile lamina up to 60cm, texture thin; pinnae oblong-lanceolate, margins serrulate to crenate, bases of pinnae broadly cuneate to truncate, assymetrical, short-stalked; sori linear extending along almost whole length of pinnae.

The combination of crenate-serrate margins and the subsessile pinna attachment (short-stalk) clearly separates Blechnum capense from the other species of Blechnum in Fernkloof.

Latin: capense = Cape of Good hope, the early name for the southern tip of Africa where this plant was first collected.