I'm puzzled about this myself - I've only ever seen this growing once (at the Roof Gardens the other day) and two different pics in people's gardens, and it always seems to be sagging along the ground when in flower, as it was in the Roof Garden. I don't know what the answer is - perhaps not pruning it hard might mean the stems would get thicker and stronger and be more able to bear the weight of the flowers.

That's interesting. I first saw it in a local garden at their open day and it was about five feet tall and didn't sag at all. I thought about less severe pruning, but the flower stems are long and I think they are without leaf buds(will have to go and check when its a bit drier out there)so I don't think they'd break if I left them. Still, can always try it and see what happens. Another surprise was that it sent up a sucker in the space I'd left between it and the mature blue on on its left - I guess I could always pot it up and pass it on to somebody. Wish it had done it on the right instead, but you can't win 'em all.