Hmm, well, not sure I agree with that. As far as feeding is concerned, they don't need much, just a general fertiliser in Spring, something like Growmore raked around the base, plus another dose six weeks later if you feel like it, but not essential. No feeding past July though. this assumes clematis in the ground, not in pots - will need feeding in containers.

A high potash feed before the buds form might be useful (in a groundplanted one) and a general fertiliser after flowering has finished is good too. But I have to say I never feed ours, but then our soil is rather rich.

I never feed clematis specifically in anyone's garden, Owdboggy, and they grow and flower perfectly well here too.

Seems to be a lot of fertiliser being poured on gardens all over the place without any reference to actual need and not just on Clematis either.

Yes, I've noticed that - and not always the right fertiliser either!