Whirligig is the nickname given to this Trailing African Daisy (osteospermum fruticosum). I snapped this picture last week at the Botanic Garden.
The Whirligig is a member of the Aster family, closely related to other mums and daisies with a single-tier of petals. It propagates well from cuttings and does well in the Southwestern United States. According to the Desert Tropicals website (Phoenix, AZ) this flower suffers in hotter climates like Phoenix, but is hardy when it comes to tolerating frost.