July's Flower of the Month
Bigleaf Hydrangea
Hydrangea macrophylla
Bigleaf hydrangeas steal the show in late spring and summer with their attractive large green leaves and showy flower clusters. The cultivars are divided into two different groups. Hortensias, informally called mopheads, have large, showy clusters of sterile blooms. Lacecaps have flat heads with tiny fertile flowers in the center surrounded by larger-petaled, sterile flowers.
Culture Provide dappled sun in the morning and protection from hot afternoon sun. Well-drained, moist soil that is rich in organic matter is best. Mulch is beneficial in summer to conserve moisture and in winter to protect canes from severe freezes. The north or east side of a building with cool, moist soils is normally a good environment.
Pests are few, and usually no spraying or other measures are necessary to maintain good health. Pruning should be done immediately after flowering. Some old canes should be removed along with any dead branches. New shoots should not be pruned because they will bear next year’s flowers.
Comments In most cultivars, of which there are many, the flower color varies according to the acidity of the soil. Flowers are blue in acid soil and pink in alkaline soil. In neutral soil the flowers are purple or lavender. White-flowered varieties do not change color with variations in soil pH.
Although there are 70-75 species of hydrangea, some that are popularly grown include: H. paniculata (panicle or peegee hydrangea), H. arborescens (smooth hydrangea), H. quericjfolia (oakleaf hydrangea), and H. anomala, (climbing hydrangea).
At a Glance
Say: hy-DRAN-jee-uh (or hy-DRAIN-juh) mak-roh-FIL-uh
Hardiness: USDA Zones 6-9
Salt tolerance: Moderate
Family: Hydrangeaceae (Hydrangea)
Size: 3-6 ft. tall/3-6 ft. wide +
Other common names: French, mophead, or lacecap hydranges; hortensia
Origin: Japan and Korea
Relatives: Hydrangea paniculata (panicle hydrangea); H. quercifolia (oakleaf hydrangea)
Propagation: Cuttings; layering