Lace cap hydrangeas (Hydrangea macrophylla), also called mophead, French or bigleaf hydrangeas, are known for their flat-topped clusters of colorful flowers. Lace cap hydrangeas are deciduous shrubs that bloom in summer and grow 3 to 6 feet tall and wide. The flowers may be pink or blue in color depending on the soil pH. Lace cap hydrangeas produce flowers on the prior year's growth, so the appropriate pruning time is different from many other flowering shrub species that bloom on new growth. Lace cap hydrangeas are low-maintenance and require little care.
Water your lace cap hydrangea once or twice each week during summer when rainfall is less than 1 inch. Keep the soil consistently and evenly moistened.
Spread a 1-inch-deep layer of organic compost on the ground beneath the hydrangea once each year in spring. Spread a 2- to 4-inch-deep layer of mulch on top of the compost. Spread the compost and mulch so that it extends to cover the area out to the branch tips, but keep the mulch about 2 inches away from the trunk.
Deadhead the hydrangea flowers as they stop blooming and fade. Remove these flowers to keep the hydrangea tidy and prevent seed formation.
Prune your lace cap hydrangea to shape it and control its size. Prune the hydrangea immediately after the flowers fade, cutting selected stems back to a healthy bud or whole branches back to the crotch at the trunk.