Ozothamnus leptophyllus (Tauhinu)
Species: O. leptophyllus
Binomial name: Ozothamnus leptophyllus
Synonym: Cassinia retorta, Cassinia leptophylla
Common names: Tauhinu, Cottonwood, Silver cottonwood.
Ozothamnus leptophyllus is a common very variable evergreen New Zealand native shrub in coastal areas, especially sand dunes. It is common in eastern areas of the North Island from North Cape southwards and is common in Wairoa, Wairarapa, Wellington, Marlborough Sounds and Central Otago. It is also found on Stewart and the Auckland Islands.
It is a bushy shrub (>2m) with small silver green leaves with fine silver hair beneath. The stems silver/white in colour. It has an attractive silver-grey appearance and from July to August it flowers in profusion with clusters of tiny cream daisy (wheel-shaped) flowers followed by down-covered seed heads. The fruits are small, dry, indehiscent one-seeded fruit with a thin wall. The seeds are dispersed by the wind. The tiny daisy seeds germinate and establish themselves easily on bare soils and in over-grazed pasture.
Ozothamnus leptophyllus is fast-growing, reaching its maximum height of 2 metres in 10–15 years. Unless their under storey plants are heavily grazed, tauhinu shrublands are usually overtopped by taller shrubs and trees, and develop into coastal broadleaved scrub. Ozothamnus leptophyllus prefers a sunny location and will tolerate temperatures down to -12.2 º C.
A crude extract from Ozothamnus leptophyllus, was shown to possess antifungal activity. Flavonoids, mainly chalcones in the leaf exudate, were isolated, some of which possessed antiviral as well as antifungal activity.
It is listed NZ Common Weeds in Colour by E.A. Uprichard.
Photographed at Te Kainga Marire - Native New Zealand Garden, New Plymouth.
The photos below were taken of populations at Cape Reinga.
Historically, Ozothamnus in New Zealand has been separated into five endemic species and seven varieties, and more recently united into a single, undivided, but polymorphic species. However, investigation leading to the recognition of a single species was limited and many botanists continue to recognise different forms within this species based on appearance and distribution. The conflicting taxonomic opinions regarding O. leptophyllus are influenced by complex patterns of variation, mostly quantitative taxonomic characters, and wide distribution with overlapping ranges.
In order to resolve the taxonomy of O. leptophyllus, it has been assessed morphological and genetic diversity within and among populations from throughout New Zealand. Unfortunately this work is still waiting to be published.
The plant in the images below is what was previously called Cassinia retorta. For now it is called Ozothamnus leptophyllus, but once the revision is published it will be a distinct taxon again.