Better late than never

I have had to move quite a few plants as I re-do the garden. These have all been potted up and left in the greenhouse for a few weeks before being moved outside, hoping they will survive long enough to be included in the  new redesigned beds.
This one was a very puny specimen that had not flowered all summer even though it was being well looked after. Now, having been uprooted and dumped in a pot, it won't stop. There must be some logic in it. somewhere