James H. Schutte
Plant Common Name
Spectacularly big showy flower clusters have made hydrangeas garden favorites. Around 70 species of shrubs, subshrubs and small trees make up the genus Hydrangea. They may be upright, mounding or climbing and have deciduous or evergreen foliage. Most are from southern and eastern Asia but quite a few species also exist in North and South America.
The leaves may be broadly oval, elliptical or lance-shaped with smooth, serrated or lobed edges. Those of some deciduous species turn bright shades in the fall. The stems and branches may be smooth, hairy or flaky and exfoliating and strong enough to support large flower clusters.
Hydrangea flower clusters may be loose or dense and have small fertile flowers towards the center and showy, four-petaled sterile flowers along the edges. The clusters may be flat, domed, conical or round, depending on the species or cultivar. Many species have flowers separated into lacecap types, which have flattened clusters edged with large sterile blooms, and hortensia or mophead types, which have large rounded clusters that consist of mostly sterile flowers. Flower color includes shades of pink, red, violet-blue, purple, lavender and white. Flower is pH dependent in some species. Alkaline soils encourage pinker flowers and acid soils bluer. The inconspicuous fruit is a capsule that splits to expel many seeds that are sometimes winged.
There are many wonder species to choose from and the most popular is the Asian big-leaf hydrangea (Hydrangea macrophylla). It has large green leaves and huge showy flower clusters with color that is pH dependent. Hydrangea paniculata is a popular large landscape shrub that produces huge pyramidal panicles of showy ivory flowers and can be trained into a tree-like form. The southeastern United States native Oakleaf Hydrangea (Hydrangea quercifolia) has huge conical flower panicles and oak-shaped leaves with soft tan undersides and brilliant crimson and bronze-purple fall color. This is just a small sample of the many garden-worthy Hydrangea.
Hardiness and culture are species dependent. Generally, Hydrangea prefer fertile, evenly moist soil with good drainage. Many types are best grown in partial sun, though some will grow in full sun. Hydrangea are ideally planted as specimen shrubs in borders, containers or woodland gardens. Climbing hydrangeas have large stems and need good support. The flowers of most are super for fresh or dried arrangements.