This article was published in the Titirangi Tatler, December 2011
One of our native plants that most Kiwis recognise is clematis, the vine that clings concealed in the tree-tops until September, when it reveals its presence with a bold display of virginal white flowers. The most familiar species is Clematis paniculata (puawhananga), named because of the large panicles of flowers that are so distinctive. But there are eight other native species with some strange oddities amongst them.
A couple of months ago in a Tatler article I briefly mentioned a bad weed species, Clematis vitalba. It is one of six exotic species that have strayed from NZ's home gardens and established in the wild.
As they all have the same basic flower and seed structure, they could all become as devastating as C. vitalba. I have waged war for several years on another species, Clematis flammula, which has a less exciting flower but is tenacious when faced with life-threatening chops or uprooting. Always there appears another shoot to grow and re-establish the population.
It seems perverse of nature to produce exotic plants that grow so easily in New Zealand, when our own native clematis is so difficult to establish in cultivation. If every native clematis planted were to thrive and survive in cultivation there would be the most stunning displays of their bold white flowers in spring. But it is not just the flowers we miss out on. The female displays her fluffy seeds in late spring which are as attractive as the flowers and, of course, provide the source of new plants when the wind has dispersed them far and wide.
The major difference between the exotic and native species is that the foreigners are all deciduous and lose their leaves in winter. The natives are all evergreen - even one of the oddities which appears leafless, Clematis afoliata. Effectively its leaf blades have been reduced to the petiole and midribs, making the plant rather like a tangle of green wire. Its ability to climb up other plants is considerably enhanced as the leaves of clematis entwine around anything that will provide support, rather like passionfruit, except passionfruit have special adaptations called tendrils to entwine around support structures, rather than modified leaves.
Another oddity is Clematis marmoraria which is not really a vine or even a shrub. Rather it is a sprawling groundcover that roots at the leaf nodes creating a dense tufted plant to about 40 cm tall. Furthermore, it demands a highly alkaline habitat, being confined in the wild to marble rock faces in N.W. Nelson.
Another disadvantage the native species have in relation to their exotic cousins is that the natives are ‘dioecious' where each plant has flowers of only one sex, so you really need to plant two or more to ensure pollination and fertile seed. The exotics, however, produce fully functional flowers with both sexes which set seed without another plant to pollinate them. No wonder they can out-perform the native species in the wild and in the garden!
Other native species each have their own peculiar charm. One is pleasantly scented despite its Latin name, Clematis foetida, meaning ‘vile smelling', one has curious brownish-mauve flowers, and one has about five distinctly different leaf forms throughout the country.
So you need to be up for a challenge to take on growing clematis, not just for a year but for life as they need protection at the very least to ensure that errant lawnmowers, well-meaning assistants, and boisterous children and pets don't cut, pull out or trip over the seemingly dead twining stem of your much loved and tended native clematis.