From the sources "Hydrangeas for American Gardens," by Michael A. Dirr (2004), and "Encyclopedia of Hydrangeas" C.J. and D.M. Van Geldere...Read Moren (2004 - Timber Press):
A slow growing plant up to 3 feet (or slightly more). Flowerheads are saucer shaped, and the ray-flowers are dark red to purple and arranged in a single ring. Fertile flowers are rosy red. Sepals are entire and heart-shaped. Flowers from July to August. Rotkehlchen means "redbreast."
From the sources "Hydrangeas for American Gardens," by Michael A. Dirr (2004), and "Encyclopedia of Hydrangeas" C.J. and D.M. Van Geldere...Read More