Plagianthus regius subsp. chathamicus is a deciduous tree up to 15 m tall. It is endemic to the Chatham Islands.

It has soft, lime green, pointed leaves with jagged margins. They are up to 7.5cm long and are wider at the base making them heart-shaped. Long sprays of tiny yellowish flowers occur from October to March with small green fruit developing December to June. The adult trunks bark is fibrous and will peel off in lace-like strips. The trees juvenile form has a non-divaricating habit (i.e. non-interlaced branches). This tree is threatened by horses, cattle, pigs. possums and by farming practices.