Astilbe thrives at Botanic Garden

This article was first published on 20 Feb 2013.

Rushing down a Chinese hillside before the light faded, I grabbed some seed from a low growing Astilbe rivularis

Fast forward 17 years and the progeny from that handful of seed here at Dunedin Botanic Garden has grown into a vigorous patch of striking foliage and swaying flower heads.  Astilbe rivularis is one of the largest astilbes which, depending on habitat and rainfall, can reach up to 2.5 metres.  In the Rhododendron Dell species border Dunedin’s moderate rainfall limits height to between 1.5 and 2 metres, as does competition from surrounding tree roots.

Most other astilbes in the Dell flower in mid summer, but A.rivularis, although now at the end of its season, is a late summer flowering species. The frothy looking yellow-white flower heads are scented and add 50 centimetres to the metre high mound of coarsely divided, dark green foliage. Earlier in the season the leaves are a bronzy colour, creating an attractive two tone effect above more mature foliage below. The leaf and flower stalks vary from yellow green to reddish, with the red colour being particularly prominent in the flower stalks.  They are also covered in coarse bronzy hairs.

From leaf emergence to late flowering A.rivularis provides a continuously changing display far exceeding my expectations at the time of its hasty collection.

Doug Thomson is curator of the Rhododendron Dell at Dunedin Botanic Garden.