What is this flower?
The plant in your photo looks like a sedum. There are several types. They flower in August -September. The flower color changes to a rust color later in the season.
Plants usually flop if grown in too much shade or in overly rich soil. They grow best in full sun. They respond well to pinching or cutting back for height control. Flowering may be delayed slightly. Plants can be pinched back to 4 inches when they are about 8 inches tall normally in early June if need be.
At this point you may be able to tie up and stake. Plants are usually left for winter interest. Old growth is pruned when you see new growth at the base of the plant in the early spring.