Things to Know About Hydrangeas

Location, Location, Location

Correct siting is the key to a happy hydrangea. Hydrangeas need water but not waterlogging. They thrive in deep, organically rich soil that drains and, preferably, a site with light shade in the afternoon. Placement in a bed facing north or east will minimize spring frost damage.

Pruning

Bigleaf hydrangeas should not be pruned hard in the spring, however messy they look. This is a major cause of flower loss. Faded flowerheads can be trimmed, and old canes can be removed to thin out a shrub, but a wholesale cutting will mean little or no blooming. Re-blooming varieties overcome this problem, but blooming is still delayed by removal of last year's growth.

Watering

Hydrangeas are among the first plants to signal dryness, but they respond quickly to a good soaking. Try to avoid wetting the leaves to minimize a leaf spot disease. Mulch lightly with screened compost or Virginia pine fines to conserve moisture.

Bloom colors

Bigleaf hydrangeas have mophead or lacecap blooms that, if not white, change color based on the amount of available aluminum in the soil. The more acidic the soil, the more aluminum is taken up and the bluer the flower. Plants in neutral to alkaline soils are pink. Local clay soils tend to be slightly acidic, not quite enough to promote a deep blue but enough for pleasing lavender-blue hues. Soil can be made more acidic by adding aluminum sulfate. Alternatively, an annual mulching with a mix of peat, compost and shredded leaves will tend to lower the pH.

Adrian Higgins