19th September 2016
I was listening to Gardeners’ Question Time (GQT) last Friday on Radio 4, and a question came up about the best time to prune clematis. The panel stated that it can be difficult to generalise as there are different classes of clematis for the purpose of pruning and in order to give an accurate answer they would need to know the variety of clematis.
I’ve touched on this subject before, I know, but in light it being raised in GQT I thought I’d return to it again especially as I was asked the same question recently.
Clematis is split into three pruning groups, a system which is based on their flowering time as well as the age of the flowering wood.
Group 1 – Prune mid to late spring after flowering and after the risk of frost has subsided.
Group 2 – Prune in February and again after flowering in early summer.
Group 3 – Prune in February/March.
The purpose of pruning is to encourage vigour (more flowers) and to prevent the clematis turning into a tangled mass of stems with its flowers blooming at the top of the plant only. I’ve seen this quite often and invariably the plant breaks and tumbles down after a period of strong wind.
Group 1 clematis’ flower on the previous season’s shoots and a variety which is in this group is ‘Armandii’ seen on the right. This variety is very vigorous and can reach up to 8 metres /24 feet. This is easy to prune and I often just use hand shears to cut this back. If it is in a real mess and needs renovating then cut back to healthy buds about 15cm/6inches off the ground. This will affect flowering and it shouldn’t be pruned hard like this again for at least three years.
Group 2 – contain the large flowered varieties which flower between May and June or perhaps July in the East Neuk. They flower on short shoots from the previous year’s growth. All these need is to be dead-headed once flowering is over, look to cut back to a large bud. A good example of a Group 2 variety is ‘Nelly Moser’ (see below left), which can grow up to 2.5 metres or about 8 ft.
Group 3 – this group flower in the latter half of the summer on the top 60cm/2ft of the current season’s growth. It is this group which can quickly get out of hand and end up in a tangled mess. These should be pruned around March to about 30cm/1ft from the ground. Remember you need to prune to a good pair of buds to encourage multiple stems. ‘Jackmanii’ (see below) is a good example and can grow up to 4m / 12ft.
If you are unsure about which group your clematis falls into for pruning then the easiest way to decide is to prune after flowering but not too hard and see what happens.