Dark Side Of The Moon Astilbe has masses of beautiful plumes of rose flowers with purple overtones at the ends of the stems from early to mid summer, which emerge from distinctive red flower buds, and which are most effective when planted in groupings. The flowers are excellent for cutting. Its attractive serrated ferny compound leaves emerge yellow in spring, turning dark brown in color with hints of coppery-bronze throughout the season. The dark red stems can be quite attractive.