One of the things that worries people most about growing clematis is the pruning. They can't remember what group their plant should be in, or what to do with it so the constant cry is 'We want one that we don't have to do anything with'. Well, folks - Bad News! They all need some pruning to a greater or lesser extent, and paradoxically, the ones that need most pruning are actually the easiest to deal with.
None of this should cause you a moments worry and I will now attempt to clarify the mysteries associated with pruning and give you a rough guide as to what you should do with orphans (clematis who have carelessly mislaid their names).
This applies to all the early flowering varieties - that is, anything that flowers from January to May. This group includes armandii, cirrhosa, alpina, macropetala and montana. If you don't want to prune them, you don't have to, but they would benefit greatly from a tidy-up after they've finished flowering. Cut out weak and dead growth, thinning out where the plant is becoming overgrown and musty.
The alpina's and macropetalas tend to retain dead leaves from the previous year, putting out new growth over the top, so this can make a plant look unsightly as it gets older.
This is also the time to control montana's, curtailing their ambitious plans for world domination. Cutting back into very old wood is not a good idea as it can introduce disease and the shock can often kill the plant, but taking out the whippy growth after flowering makes a big difference. The growth these plants make throughout the summer is what they flower on the following year, so if you prune these early flowering plants in the autumn or the late winter you will have no flowers in the spring. If any of these are wandering 30 ft up a tree, rather than risking ladders, life and limb, I would leave well alone.
The plants that fall into this category are the large flowered hybrid clematis that flower in May and June, and all the double flowered hybrids. At the end of February to mid-March, depending on the weather ( use common sense here ), trace back roughly 12 inches from the top of each stem to two fat leaf buds and cut the dead growth away above these. Some stems will be weak or diseased so cut these out entirely and on some stems you will need to go back further before you find those leaf nodes.
Bear in mind that you are working to create an attractive framework for your plant and that these varieties, like the group 1 forms, flower on growth they produced the previous year. However, because they flower later than the group 1 varieties, hard pruning these doesn't mean that they won't produce flowers at all, but what is produced will be later and smaller, doubles will be single. Selecting one or two stems to hard prune will encourage bushy growth from the base of the plant.
After pruning is completed, tie the remaining growth into shape, leaving space for the flowers and not tying too tightly.
Group three are the plants that flower later in the season on new growth produced that year - the viticellas, jackmanii and late flowering hybrids, texensis, herbaceous and other late flowering species. In late February / early March, depending on clement weather, trace each plant up from the ground and cut back just above the first set of decent leaf nodes, usually about 12 - 18 inches up.
You will notice later in the Spring that some of these varieties could have been cut back to below the ground because the growth you left is dead and new shoots have come up from below the ground. As the plant grows, tie it in to the framework or encourage it to meander through its host plant.
When taking over an established garden, or trying to identify a clematis a little rhyme is worth remembering. "If it flowers before June, don't prune". Northern gardeners could take the longest day as their 'cut off' point ( no pun intended ). However, savagely pruning a large established Jackmanii Superba for instance will probably kill the plant. The newest viable buds will be considerably more than 18 inches above the soil level, and there will be no more growth to come from under the ground. Cut back to the lowest viable leaf nodes ( however high that may be ). The plant will be leggy - grow something else in front of it!
It's not a bad idea to hard prune all new clematis at the appropriate time, regardless of their true category. It encourages a strong root growth which is most important and also encourages new shoots to grow from below the ground, making a bushier plant ( see Planting Instructions ). Pinching the new growth out also encourages bushy growth, especially on the large flowered hybrids. You sacrifice a few flowers in the first couple of years, but ultimately will have a better looking plant.
Many of the taller later flowering varieties tend to be leggy - pinching out helps a bit but not much. Better to plant something to hide the deficiency or grow them through another plant.
Look at your plants - they are practically telling you what to do. Early = 1, Mid-season = 2, Late = 3. Easy. As you become more experienced you will be able to experiment with pruning - this is just a basic guide. If you don't do it right, it's not the end of the world. You just lose flowers for that season - there are no Pruning Police (thank goodness).
This article was originally published on the web at ukclematis.co.uk, however that website is defunct at January 2009. The copyright is with the original owners of ukclematis.co.uk.