This article was published in The Fringe, June 2014
Hangehange, NZ privet.
From Madagascar to Polynesia there are 35 species of Geniostoma, but the New Zealand species is distinct and grows nowhere else. Although sometimes called NZ privet, it is not related and the common name is based on the opposite leaves having a superficially similar appearance to the exotic, weedy privet.
Hangehange is an attractive small tree growing to about three metres tall, with pale apple-green leaves which have a distinctly paler, almost white, undersurface. Hangehange's lighter shade of green contrasts with the dark greens of New Zealand's forest trees.
The small white flowers in spring have a pleasant musky scent and develop into dry capsules that split open when ripe to reveal a cluster of little seeds clinging to a central axis.
Hangehange is easily grown and most enjoys the forest edge where it can get lots of light, yet is sheltered from exposure to strong winds. If the soil is rich and moist, but not too soggy, hangehange will grow rapidly and every summer will attract lots of white-eyes and grey warblers to the ripening fruit. The small forest birds love the seed and distribute it widely ensuring that your garden is a haven for this common but little known shrub species.
Since Gondwanaland drifted apart, most New Zealand shrub genera have evolved over time to differentiate into three or more distinctive forms, now regarded as separate species. But Geniostoma has just one genus that has not evolved into such distinct forms. Throughout its range of the North Island and Cook Strait's southern coastline, there is just one form or species of hangehange.
It is true that over the years its botanical name has changed, but all the changes recognised just one species. However, two other varieties (not species) have been observed, both in the very far north. One variety on the Surville Cliffs near North Cape is a much stunted plant and the leaves are very small, largely because of the very inhospitable growing conditions for plants on the serpentine rocks. It is called Geniostoma ligustrifolium var. crassa.
The other species is even further north on the Three Kings Islands. There, a variation has evolved with noticeably larger leaves, and it is called Geniostoma ligustrifolium var. majus. Yet at both sites the common form can be found growing only a few metres away with very few hybrid plants occurring. This indicates that the common form is a distinct variety, or some people believe, a separate species from the other forms. And so maybe Geniostoma was a late starter, but is perhaps now beginning to fit the pattern that many of our plant genera have evolved into over millennia, of having within the one genus, three forms that have evolved sufficiently to now be considered separate species - a large leaved tropical-looking form, a smaller leaved form that is often the 'normal' or commonest form, and a third twiggy, stunted, often divaricating form which is one of the most distinctive features of New Zealand's flora.
While it is not recognised as a food plant, hangehange is tolerable if you eat the newest leaf tips, and if I was lost with salt and mayonnaise but not much else to eat, I think a salad of hangehange would keep me going. That is in spite of the fact that I know it is related to Strychnos from which strychnine is derived. Certainly Maori recognised its curative properties and crushed its leaves to apply as a poultice on skin sores or itchy or broken skin. Keep some hangehange in your garden for its food, medicinal or aesthetic value.