Well, they do well down here so i have loads, mop heads and lace caps in shades of pinks, blues, mauves and white. They are gorgeous.
Ive tried just dead heading in spring and also cutting back lower down and the cutting back lower down method definitely reduces flowering . Now i cut back to the top fattest buds.
We have quite a few in big half barrels and i feed every two weeks with miracle grow and they flower like crazy starting in early June and are still looking good now.