Clematis. I have not written about clematis before. This is in part that there is clematis specialist living around the corner from us and my technical knowledge on the genus is so sparse that I am worried about betraying my ignorance. I am terrified he will come and set me right. But they are such a lovely addition to the summer garden.
When I looked up clematis, I didn’t feel quite so bad about my botanical ignorance. It is a huge family with hundreds of different species (somewhere between two and three hundred or even more). Add to that the thousands of different hybrids that have been named. While ignorance may not be bliss, it is at least understandable in the face of such complexity. At least I found out that they are buttercup relatives – members of the Ranunculaceae family.
There are clematis and there are clematis. Some are altogether too vigorous. Who can forget “old man’s beard must go” on the telly? Clematis vitalba is such a strong grower that it threatens our native forest and can kill established trees. It is one garden escape that cost this country dearly. C. vitalba is not alone in its strangling and invasive personal habits but one hopes that somebody will have made those decisions long before you look at a pretty plant in the garden centre.
Clematis are equally notorious for karking it when planted out. That magnificent specimen in a pot with a frame covered in flowers can disappear before your very eyes when transferred to the garden. The problem is usually “clematis wilt”, reportedly a fungal affliction. If you spot it, cut back to healthy leaves, or even to the base of the plant if the whole thing is affected. Remove the diseased sections, cross your fingers and wait. Often, the plant will shoot again but it can take a while and the clematis roots can survive a year or longer without shoots above ground.
These are the only plants I know where the advice is to plant deeper in the ground than in the pot – around 8cm deeper is good. This is largely protection against the dreaded wilt, as far as I can see, so follow the advice. Like most climbers, they prefer their roots in cool, humus rich soil with adequate moisture levels but their heads in the sun. This is not always that easy to find, especially as you have to combine it with something for them to climb up. Once away, they can get purchase and twine onto surfaces that are not smooth – their instinct is to reach for the sun so most will climb if possible.
As garden plants, I favour the hybrids and the viticella types. We have a fair number twining their way through shrubs in mixed borders and they never fail to delight when they flower. You need to make sure that you don’t have overly rampant varieties when they are expected to co-exist with other plants. I took out what I think were texensis types – given to me as ground cover but distinctly shy on flowering, bell-shaped which I was not so keen on, and given to choking habits. I did not think they justified their position but there may be better texensis varieties available.
We have several growing under cover. Everybody admires “Niobe” in bloom. She has large flowers in deep burgundy but she proved damn difficult in the garden and it has taken several attempts over a fair number of years before we had a plant performing well, scrambling through evergreen azaleas. Planted in the ground but under cover with just some rain run-off to keep the roots moist, she has been much more reliable.
At the opposite end of the scale, the lovely, late-flowering yellow C. tangutica threatened a takeover bid in the garden but when relocated to a trellis under cover, behaved perfectly in comparative isolation.
Often they can be combined with other climbers to extend flowering interest. We have clematis planted successfully with wisteria, Trachelospermum jasminoides and schizophragma. The latter two plants, for those who struggle with plant names, are a garden-friendly jasmine-type plant and a variation on the climbing hydrangea.
If you cut back most of the hybrids to just above ground level after flowering, feed and water them, you can encourage a second coming about six weeks later. Now is the right time to try this if you have some that have, as we say, ‘passed over’. However, it won’t work with the early spring flowering Clematis montanas. We don’t have C. montana any longer (it is a bit rampant for the garden, being better at covering old water tanks or sheds. It is once flowering only and needs different pruning treatment, if any. Most of the others I cut back to maybe 30cm above ground in winter and they are fine. Once established, they are easy and reliable and bring delight in spring and summer.
We have some lovely native clematis in this country but they are a story in their own right for another time.
If you want to know more about different types of clematis or maybe even buy mail order, my neighbour is http://www.mrclematis.co.nz/ (email: email@example.com). He produces a phenomenal range and has a passion and knowledge for the genus way beyond mine.
First published in the Waikato Times and reprinted here with their permission.