Advice from Darren Morgan –
Hydrangeas are the bright stars of the summer landscape. Their immense show of flowers can persist for months, filling the gap between spring flowering shrubs and fall leaf and berry displays.
Panicle forming hydrangeas (Hydrangea paniculata and Hydrangea quercifolia) are dazzling in sunny situations. Their upright spikes of white flowers slowly develop interesting finished colors, ranging from bright chartreuse green to hot pinky-red to deep burgundy. All varieties start out white, and the mature flower color is determined by variety, not soil.
Traditional hydrangeas – the mop head and lace-cap types of Hydrangea macrophylla – are at their best in a shady site. They come in a dazzling array of soft or intense colors, including soft or bright pinks, reds, blues, purples, whites, and even red-streaked green bicolors. You can control the color of some (but not all) of these varieties by changing the soil pH. To encourage pink colors, work a cup of lime into the soil around the plant in mid to late spring. To encourage blue to purple tones, add elemental sulfur or aluminum sulfate instead, following label directions.
Monitor the colors of the first few flowers to form, and add more pH changers as needed. It is normal for the flowers to exhibit some variety in color, and for the colors to drift a bit through the flowering season. Individual flowers change color as they age, fading to green, tan, or burgundy. The faded flowers are often quite attractive in their own right, but many modern hydrangea varieties – such as the Endless Summer series – will rebloom if spent flowers are removed.