Posted: 17/01/2015 at 14:54
Your clematis will be a tangutica or orientalis and is a Group 3, BUT, it is best unpruned until about April when you should see some new green shoots on the plant, then cut it back to about 3 ft.
Most Group 3 are chopped back almost to the ground in February, but the yellows in my experience are best treated differently.
Also, you should still have plenty of seed heads on your plant, the birds love these for lining their nests. ( try sowing a few in a zippy freezer bag with damp vermiculite, they are easy )
" If it flowers before June, do not prune ", means that the atragenes, montanas, Early Large Flowered Hybrids, should not be pruned hard back as they flower on last year's wood.