Our native plants: Mountain cottonwood

Despite its common names of mountain cottonwood or silver heather, Ozmanthus vauvilliersii (formerly Cassinia vauvilliersii and also known as Ozothamnus leptophyllus) is found all over the place – my photo was taken on the walk from Eastbourne to Pencarrow lighthouse with the plant growing either side of the track which, for the first hour at least, is right beside Wellington Harbour.

The Hebe Society (based in the UK) lists it and I was certainly wondering if it was a hebe as I looked at it, something about the compact leaves. It’s almost redundant to say it copes with harsh conditions and copes with everything from snow to salt-spray (the track would easily be inundated in a good blow). A good plant for a dry garden.

Mountain cottonwood flowers from December to April, but this plant was photographed in July and had buds on it, as well as spent flower heads. Photo: Sandra Simpson.

In his book The Cultivation of New Zealand Trees and Shrubs (Raupo, 2011) Lawrie Metcalf says: “Five former species within the genus Cassinia, now reclassified as Ozmanthus, are so variable and have so few distinguishing characters that there has been a tendency to regard all of them as simply variants of just one species, O. leptophyllus … All parts of the shrub, including the flowers, have quite a strong scent.”

Known by Maori as tauhinu, the shrub is, Metcalf says, a good nurse plant for more tender, permanent plantings (just as gorse is too). Its growth is fairly rapid and so its life cycle reasonably short. Its range in New Zealand is from about northern Waikato to southern Marlborough. Massey University reports that it can be a weed problem for farmers in eastern districts.

But everything on the plant has its place and a chapter in The Biology of Wetas, King Crickets and their Allies (CABI Books, 2001), edited by L H Field, notes weta insects have a special relationship with tauhinu, with the weta found on plants at night throughout the year, and feeding on the new shoots and flowers. (Click on the ‘weta’ link to read more about these amazing insects.)