Panicle Hydrangea

Panicle hydrangea (Hydrangea paniculata, Hydrangeaceae) is a fast-growing deciduous shrub or small tree from Japan and eastern China, reaching 7 to 25 feet tall with a spread of about 13 feet and a vase-shaped form. Conical flower panicles (15 to 20 centimeters) appear from July through September on new wood, opening white and aging through pink tones. It is the most cold-hardy of the commonly grown hydrangeas.

Panicle hydrangea grows in sun to part shade on wet-tolerant soils (pH 4.5 to 8.5) with high water needs, hardy in Zones 3a to 8b. It blooms on new wood; prune in late winter. Disease pressure (13 associations) and pest associations (root weevil, foliar nematode, aphids, mites) match the genus. Cultivars include 'Angel Blush' (white aging to rosy-red, 8 to 12 feet), 'Pink Diamond' (white aging to pink, 5 to 10 feet), and 'Unique' (6 to 10 feet).

Panicle hydrangea is one of the best flowering shrubs for the Puget Sound lowlands and the one hydrangea that genuinely thrives in full sun here. It blooms on new wood, which means pruning happens in late winter, not after flowering. That single fact eliminates the most common hydrangea mistake in this region. The flowers emerge white in July-August and age to pink, then dry to tan and persist into winter. Thirteen diseases are documented but only powdery mildew is common, and it is cosmetic. Root weevil is the one pest to watch, feeding on roots at night. The plant tolerates our wet soils and works beautifully in rain gardens. ‘Pink Diamond' and 'Unique’ are reliable locally. For a flowering shrub that handles poorly drained lowland soils, wet winters, and summer heat, this is the safest bet in the hydrangea genus.

— Chris Welch, ISA Certified Arborist