By Barbarak
North Yorkshire,
United Kingdom 
Clematis Florida Plena pruning conundrum. I bought one of these plants 2 years ago that was trained around a short trellis frame. When I put it into the garden I untangled the framework and it flowered well last summer without any pruning. The websites info seems contradictory as to whether it is Gp2 or 3. At this moment it has some top growth about 3 ft from ground but there is only 1 single stem from the ground. Should I treat as Gp 3 and prune it down to 1 ft or leave it alone.
Thanks.
9 Feb, 2019
Answers
On the other hand, I treat it as Group 3 and cut it back to about two feet in early spring. It still gets to ten feet by the end of the season
9 Feb, 2019
It is technically a Prune group 2 type, but if you only have one main stem coming up from the roots, chop it down to encourage new stems, just for this year. Its usual to do this the first spring after they've been planted, and thereafter prune as Prune group 2, but as you've not done it, I suggest you do it now. Embedded link in the RHS link below to Prune group 2 instructions...
https://www.rhs.org.uk/Plants/178200/i-Clematis-florida-i-var-i-flore-pleno-i-Plena-(d)/Details
9 Feb, 2019