Posted: 29/05/2016 at 16:48
I agree with the above......they grow into vast plants if they are happy and the only pruning you need to do is to remove any bad/damaged stems.
IME, the red flowered ones tend to be larger plants on the whole. Mine had more than 50 flowers on last year and looks set to beat it's own record this year.
I also have a pink one and altho it is having a sulk this year, that too is a magnificent plant when in full flower.
Mine overwinter in an unheated G/H with fleece protection when necessary but spend a good part of the year outside.
If the flowers are pollinated, you often find "fruit" forming......open it up and spread the whole mess on some gritty/perlite/compost mix and they will germinate given a bit of bottom heat.