Asplenium nidus forms large simple fronds visually similar to banana leaves, with the fronds growing to 50-150 centimetres (20-59 in) long and 10-20 centimetres (3.9-7.9 in) broad. They are light green, often crinkled, with a black midrib, and exhibit circinate vernation. Spores develop in sori on the underside of the fronds. These sori form long rows extending out from the midrib on the back of the outer part of the lamina (frond). The fronds roll back as they brown and create a massive leaf nest in the branches and trunks of trees.