Diamond RougePanicle Hydrangea has abundant, long lasting, rounded flower heads that start white and progress to pink, intense raspberry red, and finally wine red. Flowers start blooming in July and take on red coloration earlier in the season than other pink panicle hydrangeas, with fall color at its best when night temperatures are 10 degrees cooler than day temperatures. Diamond Rougeis a mid-size hydrangea, working beautifully as a focal point or small hedge.