The South Island's kowhai are a taonga worth preserving, writes Kath Graham.
Kowhai grow throughout the country, except on Stewart Island. And while we now have eight separate species, only one is indigenous to most of the South Island.
It is known as the ''South Island kowhai'', or Sophora microphylla.
This species, in good conditions, will be flowering already, but in other years won't flower until September or October. While the South Island kowhai is not endangered, like all kowhai it faces threats including hybridisation and competition from garden varieties, many of which flower at the same time, and the destruction or degradation of habitat.
The name Sophora comes from the Arabic name for a leguminous tree. The Sophora genus dispersed around the southern hemisphere on ocean currents, and arrived on our shores as one species, to later diverge into the eight recognised today. Like its Sophora relatives in other parts of the world, it has pinnate leaves and pea-shaped flowers, which ripen into pods.
Kowhai is the Maori word for our Sophora species, and also the word for ''yellow''.
Maori prized kowhai for its medicinal uses. It is thought the S. chathamica that are found at a few sites in Wellington, were brought there from further north by the tribes that invaded Wellington in the 19th century because they were valued for such things.
It was the bark from one of the North Island kowhai species that was reportedly used to save the leg of All Black George Nepia from amputation after he got blood poisoning.*
Some of the kowhai at Prospect Park, Dunedin were chopped down last year by the council, among which was a North Island species, possibly S. chathamica.
Although I am no expert, I counted 220 growth rings on the bole of one of these trees and the same number on a South Island kowhai stump. This raises a number of questions: how did North Island kowhai come to be growing in Dunedin? Who planted them?
Apart from the historic interest in the heritage of some imported kowhai in Prospect Park, our main interest should rightly be in our local kowhai, especially inasmuch as they retain, or have developed, South Island kowhai's most defining characteristic, the divaricating or flexuous juvenile stage not found in the other species.
When young, twiggy branches grow in all directions so that the young kowhai bush resembles a roll of wire netting.
The second most widespread species, the North Island kowhai, is found only in the north, whereas the South Island kowhai (the most widespread species) is actually found throughout the country. But where it grows with other kowhai species, it is known to hybridise, and the further north it is found, the less it retains the divaricating juvenile form.
In the South, where it has had no other species to hybridise with, and where the climate is colder, the trees retain the characteristic juvenile stage. However, as long as gardens and council plantings are made up of species that are not local, some will hybridise with local kowhai, and will ultimately escape from gardens to compete with naturally occurring kowhai.
Of more immediate concern, in places such as Maungatua where there are some magnificent kowhai groves, as well as in a reserve in Macandrew Bay, no juvenile or young trees are to be found.
While seeds are produced en masse by mature trees, there are no intermediate trees between tiny seedlings a few centimetres tall and the 20m mature forest specimens.
This is the result of grazing and browsing by animals, and it means that as the older trees die off, the numbers of kowhai will decline.
On Mt Watkin, where there is a forest of kowhai, the ground is so badly ploughed over by wild pigs young trees stand little chance of growing at all. If these areas are anything to go by, unless the understorey of our forests are protected, then kowhai are headed for a devastating decline over the next several decades.
These areas need protection from grazing and browsing animals so we can ensure retention of a healthy population of kowhai that will survive into the future.
But we can do even better still. Because the islands of New Zealand have only recently been colonised by people, we can both identify our natural flora and have the opportunity to preserve it. And because it is still early days in the planting of native garden varieties, especially the slower growing and slower spreading plants, we are still able to prevent the insidious, almost invisible spread of and takeover by horticultural natives in our natural habitats.
A commitment to plant only local natives, especially in areas where garden plants are likely to hybridise with wild plants, will reduce the effect of hybridisation and minimise the spread of non-local natives, thus preserving and protecting the natural character of our flora.
And most importantly, we need a commitment to properly protect our forest habitats in order to ensure a healthy stock of kowhai of all ages, so the species can be retained as one of our dominant trees in the forests and natural areas of this region.
Kath Graham is a coastal Otago-based botanical artist.
*Maori Healing and Herbal: New Zealand Ethnobotanical Sourcebook, by Murdoch Riley (1994).
Kowhai species in NZ
South Island kowhai can be identified by its small leaves and divaricating or flexuous form as a young tree. As well as this, in the South Island, the prostrate kowhai (S. prostrata), occurs in drier parts of Canterbury; Nelson has a species which grows on its limestone cliffs called Sophora longicarinata; Cook Strait has a species which is only found on islands in the strait, called Sophora molloyi, (now commonly grown and sold by garden centres throughout the country).
The rest of the species, Sophora tetraptera, S. godleyii, S. chathamica and S. fulvida, are North Island varieties. S. tetraptera is also known as North Island kowhai, and is the next most well known and widely planted species after the South Island kowhai. It has larger leaves and flowers, does not divaricate as a juvenile, and flowers in September and October in this part of the country.
