1. (noun) swamp aster, Olearia semidentata - a beautiful daisy endemic to the Chatham Islands where it is found in peaty ground and bogs. Can grow 2–3 m tall. Flowers appear over the summer months from November, fruiting follows in January and February. The colour of the ray florets is variable, often starting purple and fading to pink or white over time. The disc florets are dark purple. Leaves are dark green with white tomentum (a covering of short dense hairs) underneath and younger stems are often covered with the same.