Sphaeropteris medullaris, synonym Cyathea medullaris, commonly known as mamaku or black tree fern, is a large tree fern up to 20 m tall. The trunk is black and covered with distinctive hexagonal stipe bases. The fronds may be up to 5 m long, and arch upwards from the crown. Dead fronds are shed except in very young plants. The primary pinnae are from 40 cm to 1 m long, and the undersides have scales with spines along their margins. The stipes are thick, black, very rough to the touch, and are similarly covered in black scales with marginal spines. S. medullaris can be readily distinguished from related species by the hexagonal stipe scars on the trunk, and by the scales with spines on their margins.

Sphaeropteris medullaris will grow from fresh spores. Plants are easy to transplant when they are young. They are hardy in various conditions once established.

Location: Sun or part sun

Hardiness zones: 8-11

Spores per packet: Approximately 20 spores (very tiny)