Shades of green
In this issue we have a story on how New Zealand’s native trees and native birds have evolved alongside one another.
As you probably know already, the majority of New Zealand native trees are evergreen. In fact only 11 species of New Zealand plants are consistently fully winter deciduous (fun pub quiz question: name them all). There are just another 11 that would be described as semi-deciduous, with their degree of leaf loss varying according to their site and location, and Sophora microphylla and Sophora tetraptera are what is called brevideciduous which means they keep their leaves over winter but lose them in spring, and then flower before the flush of new leaves form.
In the story on the co-evolution of our flora and fauna, the plant evolutionary biologist Janice Lord, an associate professor in the Department of Botany at Otago University, gives one of the reasons that we have such a high rate of evergreen trees, which I, for one, did not know. Because of our island nation’s temperate maritime climate, summers can be unpredictable, she points out. Under these conditions it is better for the tree to produce weather-resistant small leaves or needles which it can hang on to during winter. Deciduous trees, on the other hand, tend to have larger leaves which give them a bigger surface area for absorbing energy from sunlight through photosynthesis but those leaves are also more vulnerable to damage in cold winters. So those trees have evolved to shed their leaves as it gets cold. “Being deciduous only serves the plant when there are definite seasons with really different temperatures,” Janice says.
Evergreen trees, of course, look similar year round. And that has possibly contributed to the idea that our native plants were, well, not particularly exciting. I was talking to someone the other day who worked in a garden centre in the 1970s and 1980s, and I asked how the native plants were viewed at the time. He said they were generally considered to be fairly second rate back then – good for a functional area, which might be difficult to access or where you didn’t want to do much maintenance but nowhere near as exciting for gardeners to grow. Even in the garden centre, he said, the few natives that were for sale – which were primarily variegated forms of Coprosma repens back then, apparently – were tucked at the back out of the way. Which was fair enough, he told me, since they looked pretty motley and you wouldn’t want them on display.
I think that attitude has changed in the intervening decades. I hear often from gardeners who love native plants and grow them as part of their gardens or exclusively. Now of course, thanks to some visionary plantsmen and women, we have an incredible and beautiful range of native plants available (indeed, if you are looking for inspiration as to how to use native plants in your own garden, I strongly recommend you visit Broadfield Garden in Rolleston, Canterbury if you get the opportunity, as owner and gardener David Hobbs has created a stunning garden of New Zealand plants, both natives and those bred here from imported species, including a wonderful 120m long English-style border that should refute once and for all the idea that our native plants are dull or monochrome).
This month I’d love for everyone to get out for a winter walk somewhere and take the chance to really look at our native plants. As with everything really, the more you do, the more they reward your interest. They offer a wonderful range of textures, from the lushness of our ferns to the drifts of our native grasses. There are more colours than you might think, from the silvery greys of astelia to the dazzling golds of Libertia peregrinans. And there is such a range of leaf shapes to be seen: look for heart-shaped leaves (kawakawa), egg-shaped leaves (lacebark or houhere), kidney-shaped leaves (kidney fern or raurenga), round leaves (coprosma or mikimiki), and pinnately lobed leaves (hound’s tongue fern or pāraharaha).
Do you grow natives in your garden? If so, which ones? If not, why not? Email your views to me at mailbox@nzgardener.co.nz.