Lately, a few people have been asking me how to prune their clematis and if they should be doing it now.
My pat answer to both questions is always: “Well, that depends.”
I hate to be vague, but when it comes to clematis and pruning, you really do need to know which one you have.
This is because clematis are divided into three different categories and one of those three categories is split into two. Each of these categories has different pruning methods and the pruning is done at different times.
This is why hanging onto your plant tags is very helpful if you cannot rely on your memory. But even if you do not still have your plant tags after the last spring cleaning of the garage or toolshed, you can make an educated guess which group your clematis belongs to IF you can remember when and for how long it blooms.
Group A (or 1): These are your early-flowering clematis, which form their buds on the previous year’s growth for blooms in early spring … usually April through May.
Pruning time for this group is immediately after the bloom is finished but no later than the end of July to allow ample time for the new growth to develop and harden for next year’s buds. Clematis that fall into this group include C. montana, C. armandii (the evergreen clematis), C. alpina, C. macropetala (downy clematis) and a host of others.
Group B (or 2): These are your beautiful, large-flowered hybrid clematis. But here is where it gets a little tricky.
Some of the Group B clematis are in sub-group B1 (or 2A) and some are in sub-group B2 (or 2B) and both of these sub-groups have different pruning requirements.
Clematis in the B1 group bloom on the previous year’s growth, same as the Group As but usually in mid-June through July. They also may rebloom later in the season on the current year’s new growth … in late August into September. Group B1 is pruned in late February to early March, cutting the stems back to the uppermost pairing of large, fat buds.
Clematis in this group include the ever-popular ‘Nelly Moser’, the ‘Duchess of Edinburgh’, ‘Countess of Lovelace’, ‘Belle of Woking’, ‘Crystal Fountain’ and ‘Beauty of Worcester’…to name but a few.
Most of the double-flowered clematis fall in the B1 sub-group, as they flower on old wood from the previous season. However, there are exceptions. ‘Arctic Queen’ blooms from June through to September so falls into the B2 group with its slightly wishy-washy pruning requirements.
All of the B2 sub-group bloom longer than the B1s … usually June straight through into September but only once throughout the season. And the “wishy-washy” pruning technique is actually up to you. You can decide whether to prune it as a B1 or prune as if it were in Group C.
Another option is to prune it as a B1 one year and a C the next. Again, your choice. The B2 clematis varieties include the brilliant red-flowered ‘Niobe’, ‘Henryi’, ‘Jackmanii Alba’, ‘Jackmanii Rubra’, plus others.
So how to prune the Group C clematis?
This is the easiest group of all. Just cut all the stems back to eight to 12 inches (25-30 cm) above soil level in late February … then stand back. New growth will begin as soon as the weather warms a little and the vine will climb to its full, lush height in no time at all.
Flowering will commence in mid- to late June and go straight through until frost. Clematis in Group C include C. viticella, ‘Etoile Violette’, C. heracleifolia davidiana and ‘Madame Julia Correvon’.
If you still cannot remember the name of your clematis or exactly when it flowers, don’t sweat. Just let it go this year, but do remove the ugly dead leaves … carefully by rubbing with your fingers. And be sure to write down when it flowers so you will know when to prune it next year.
Leslie Cox co-owns Growing Concern Cottage Garden in Black Creek. Her website is at www.duchessofdirt.ca.