Hydrangea arborescens 'Ryan Gainey'
Common Name: smooth hydrangea 
Type: Deciduous shrub
Family: Hydrangeaceae
Zone: 3 to 9
Height: 3.00 to 4.00 feet
Spread: 3.00 to 4.00 feet
Bloom Time: June to September
Bloom Description: White
Sun: Part shade
Water: Medium
Maintenance: Low
Suggested Use: Hedge, Rain Garden
Flower: Showy
Tolerate: Rabbit, Erosion, Clay Soil, Dry Soil, Wet Soil, Shallow-Rocky Soil


Easily grown in average, medium moisture, well-drained soils in part shade. Tolerates full sun only if grown with consistent moisture. Intolerant of drought, with foliage tending to decline considerably in dry conditions. Plants may die to the ground in harsh winters. Bloom occurs on new wood, so plants may be pruned back close to the ground in late winter to revitalize and to encourage vigorous stem growth and best form. If not pruned back, any weakened and/or damaged stems should be removed in early spring.

Noteworthy Characteristics

Hydrangea arborescens, commonly known as smooth hydrangea or wild hydrangea, is a loosely and widely branched deciduous shrub that typically grows to 3-6’ (less frequently to 10’) tall. It is native to moist or rocky wooded slopes, ravines, streambanks and bluff bases from New York to Florida west to Iowa, Missouri, Oklahoma and Louisiana. Gray-brown stems are clad with opposite, broad egg-shaped to rounded, sharply toothed, dark green leaves (2-6” long) with pale green undersides. Leaves turn yellow in fall. Tiny white fertile flowers bloom in May-July in flattened hairy clusters (corymbs to 2-6”across). Scattered continuing flowering may occur throughout summer to September. A few large sterile flowers usually appear at the cluster margins (usually not enough for a quality lacecap effect). Flowers give way to dehiscent seed capsules which ripen in October-November.

Genus name comes from hydor meaning water and aggeion meaning vessel in reference to the cup-like capsular fruit.

Specific epithet comes from arbor meaning tree in reference to the similarity of this shrub to a small tree.

‘Ryan Gainey’ is a compact cultivar that typically grows to 3 1/2’ tall. Unlike the straight species, this cultivar features symmetrical rounded snowball-like flowerheads (corymbs) densely packed with showy white sterile florets (only a sprinkling of non-showy fertile florets). This is an upright, free-branching, rounded shrub with flower heads resembling a medium-sized ‘Annabelle’ (see H. arborescens ‘Annabelle’) but with the advantage of having stronger flowering stems that are less likely to flop when flower clusters are moistened with rain or buffeted by strong winds. It has darker green foliage, smaller but more numerous flowers and thicker stems than plants of the species. Flowers bloom in June for up to two months (sometimes into early September). Flowers contrast well with the ovate to elliptic, serrate, dark green leaves. Cultivar name honors garden enthusiast, garden designer and author Ryan Gainey of Decatur, Georgia.


No serious insect or disease problems. Many species of hydrangea, including this one, are susceptible to bud blight, bacterial wilt, leaf spots, mold, rust and powdery mildew. Watch for aphids, mites, scale and nematodes. Pruning stems back to the ground in late winter each year helps promote stem vigor.

Garden Uses

Mass or group in part shade areas of the mixed shrub border, woodland garden or as background for a perennial border. Naturalize in woodland or native plant gardens. Named cultivars often make showy specimens.