Clematis Pinching

Thanks Bob ,I pinched the tops of the two big stems yesterday hoping that will encourage it to throw up some more stems from the bottom. Your right it is only a young plant this is its second year but it doesn't really have any low growth you might be looking at the top of a lavender it's growing behind.
If I chop it lower down say second leaf up will it grow two stems from were I chop it do you think.All new to me don't know how it works.

 

I mean plenty of leaves, hence possible growth points. I'd cut it back like this, or a set of leaves lower:

 

OK so is the hope then that it will send shoots from were the remaining leaves join the stems.
And new shoots from lower down .

 

Yes, it will grow 2 new shoots from the base of the leaves just beneath each cut, so you'll have 4 new stems. If those new shoots are pinched back to a pair of leaves some weeks later, you'll get even more. Try to train the new growth as horizontal as possible, but don't force anything, as new shoots are extremely brittle.
You may even get new growth from below ground after cutting back, which would be ideal.

 

I agree with @BobTG - cutting back properly encourages those new stems from below ground on the Group 2s and 3s.
I can understand your reluctance @Dropmore , but it's better for the plant later on, as it matures and strengthens up.
If the plant you bought was a young one - ie from a supermarket or similar, they benefit from being grown on/potted on until they're more mature before planting out.
I'm at the point of giving up with many of the larger flowering types though, as my conditions here make it very difficult for them when the new growth appears. Slugs are always an ongoing nightmare, and the mild winters are making it even worse than before, but it's too expensive to keep replacing them if they can't cope. Even ones which generally cope well, get attacked on those maturing stems because they graze on them, and that sees them off.

 

Thanks Bob and fairygirl, it's a viticella Prince George and according to thorncroft groes the same size as etoile violette , any way I have taken your advice and given it the chop.

 

Update
It is growing two new shoots from the base of the leaves just below each cut exactly like you all said it would, so we'll done everyone and another lesson learnt
Thank you

 

That's great @Dropmore . I can understand how it can be a bit nerve wracking doing it though!
Hope it comes away well for you and you get a nice display later.

 

Sorry to bob in, but may I ask, if my Clem's are starting to flower now, (a) what group are they and (b) is it too late to chop them to encourage bushing out?

 

@Meomye if your clematis are flowering now and have large flowers then it is most likely that they are Group 2. Don't prune them or you will lose the flowers. They can be tidied up and pruned a little after flowering and they could well produce some late summer flowers.

Group 3 clematis, which are summer and autumn flowering and usually have smaller flowers, but lots of them, are best pruned late winter down to about 6 to 8 inches.

 

Thank you for clarification @Busy-Lizzie

 

Many Group 1s are still flowering. If you have a pic, that will help with further advice. They really only need pruning if outgrowing their space.

 

Yes, could be either Group 1, or Group 2.

 

My Montanas, group 1, in Norfolk, have finished flowering. They don't need pruning unless getting too big, in which case do it straight after flowering.

 

The early macropetala I have is often not finished until the end of this month - it doesn't start flowering until late April/early May. Lots of those earlier types flower from April through to late May, but I expect it also depends on location.
Montanas are in full flower here just now. When I grew them, they were often still flowering until early June.