P&PDL Picture of the Week for
June 20, 2005

Hydrangea Flowers - Red, White, or Blue?

Rosie Lerner, Extension Consumer Horticulturist, Department of Horticulture, Purdue University

Hydrangeas are popular but can be challenging for Indiana gardeners. There are numerous species and cultivars that show amazingly diverse flowering characteristics, especially color. Depending on the species, cultivar and environmental conditions, the flowers may be pink to red, blue to purple, cream to white, or some shade thereof.

Many gardeners are awestruck when they see a gorgeous blue-flowering hydrangea. Such a specimen is no doubt one of the big-leaf hydrangeas, known botanically as Hydrangea macrophylla, which has flowers that will be blue in acid pH soil, and pink in alkaline pH soil. Since this species typically flowers on old wood and is usually killed to the ground in much of Indiana, this plant often disappoints as it produces abundant new foliage but no flowers. If it does manage to bloom, much of Indiana has alkaline soil, so flowers are more likely to be pink unless the gardener treats the soil to lower pH substantially. There are some promising newer cultivars that bloom on both old and new wood, such as 'Endless Summer'.

The hardier species that flower mostly on new wood include H. paniculata and H. arborescens, and have white blooms. For more information on the different types of hydrangeas in Indiana, see http://www.hort.purdue.edu/ext/hydrangea.html.

Click on image to enlarge

Hydrangea species display at 2005 Chelsea Flower Shower

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service