Posted: 22/01/2015 at 16:19
I have always worked on the basis that Group 2 clems are pruned after their first flush of flowers is finished in May/June and then fed generously to encourage a second flush of flowers at the end of summer. At this pruning, its usual just to remove dead flowers and then maybe take out one or two stems back to the base to encourage fresh growth and vigour.
However, in my garden, I treat Group 2s like group 3s as they always get their tops frozen to bits in my winters so anime form mid Feb to mid March, depending on the weather, I prune them back to about 9 inches above the ground and give them a generous dollop of proper clematis food and a mulch of well rotted garden compost. It usually means they flower a bit later but then I dead head and they keep flowering for months. Nelly Moser flowered till December last year and Rahvarinne till November.