The best native climber

Reports have been coming in to me that the clematis is in flower on the Rimutaka Hill road. Friend after friend has been telling me that the trees are wreathed with the shining white flowers of Clematis paniculata, so this weekend I made a short trip out into the countryside to see whether the rumours are true.
Sure enough, the puawhananga are in flower and what a brilliant sight they make – surely the most brilliant of the native clematis, and also one of the most attractive of all native flowering plants.
There are hundreds of Clematis species scattered all over the temperate world, and of course, very many more hybrids and varieties. New Zealand has its share of these species and they include some very interesting plants, but the star is the puawhananga.
For many years this was hardly grown in gardens even though it was widely known. That may be due to simple sexual discrimination. Female and male flowers are borne on different plants. The male flowers are bigger and more attractive. In the past nurserymen have tended to offer plants that have been gathered from the wild and they take a long time to flower, then, when they do flower, the flowers have not been of the best quality.
Fortunately, nurserymen have learnt how to grow these beauties from cuttings (it is not easy from wild plants) and now we can have selected forms with known characteristics.
Probably the best of these is ‘Serenity,’ selected from wild plants growing in Canterbury and with flowers that can be over 110 mm wide.
To grow any Clematis paniculata properly you need to bear in mind the conditions it favours in the wild. To put it crudely, it needs its head in the sun and its bum in the shade.
In the wild, these plants grow in the litter at the bottom of the forest floor. They grow in friable humus-rich soil that is both cool and, usually at least, moist. In the garden, they need similar conditions, with perhaps a deep mulch on the soil. It pays to plant this near a tree or shrub that it can scramble up, although it will grow perfectly well along a fence. If grown along a fence do remember that it will need a cool root run and cannot cope with hot and dry soil conditions.
In the wild these plants grow with very long stems – in fact, it is sometimes very hard to track back from the flowers to see where the roots are. As they wander through the scrub, they tend to lose many leaves from the lower portions of the stems and this can be a problem in the garden if the plant is grown along a fence.
‘Serenity’ is, as you would expect from a southern plant, a hardy form of this species but a hybrid based on C. paniculata is even hardier. ‘Purity’ also originates from Canterbury and is perhaps one of the hardiest of all evergreen flowering climbers.
It flowers later than ‘Serenity’ – mid-October rather than mid-September- and its flowers are slightly tinted, indicative of its hybrid origin. The flowers have a distinct green colouring when first open, but fade to a pale cream if grown in light shade. In full sun the flowers turn pure white.
Again, this needs a deep cool root run to succeed well, but once established can cope with extensive periods of drought. However, it cannot cope with a dry and warm site so plant in under shrubs or trees for best display.
This is better than ‘Serenity’ for fence line plantings as it has long flowering stems that droop down, giving a dramatic floral display. If you decide to grow it along a fence line just bear in mind that this one loses foliage along the stem too, so it probably pays to cut it back by about a half after each flowering.