Pink or purple-blue lacecap flowers, a ring of large showy florets around a center of small fertile flowers, open on this mountain hydrangea in early summer. Hydrangea serrata Tuff Stuff™ 'MAK20' grows 2 to 3 feet tall and wide in part sun to part shade, hardy from Zone 5 through Zone 8.
It reblooms, flowering on old and new wood, so a second round follows the first and continues toward frost. Bees visit the fertile flowers at the center of each flower head.
Mountain hydrangeas change color with soil pH the same way bigleaf hydrangeas do. Acidic soil below about 6.0 gives blue, alkaline above 7.0 gives pink, and the range between produces purple or a mix of pink and blue on the same plant. Aluminum sulfate pushes flowers toward blue and garden lime pushes them toward pink, and either takes a season to show.
Hydrangea serrata is a close relative of bigleaf hydrangea, with smaller leaves, finer stems, and flower buds that hold up to cold much better. Buds formed on old wood in late summer come through hard winters and late spring frosts that often cost a bigleaf hydrangea its bloom, and that bud hardiness is the main reason to choose a mountain hydrangea. Prune in summer after the first flowering and no later than August, since cutting in fall or early spring removes next year's buds. Dead stems can come out in spring, once new growth shows which ones are dead.
The mounded habit suits a foundation bed, the front of a border, or a large container, and the leaves turn red and burgundy in fall.
