Oakleaf hydrangeas (Hydrangea quercifolia), native to the Southeastern United States, are deciduous ornamental shrubs hardy to USDA Zone 5. Oakleaf hydrangeas tolerate slightly sunnier and drier locations than the common hydrangea (Hydrangea macrophylla). The species name "quercifolia" comes from the leaves, which are oak-like in shape.
Oakleaf hygrangeas, with an upright habit, have shedding bark on old stems and an asymmetrical canopy. A moderately fast grower, oak leaf hydrangeas form colonies to 8 feet tall with equal or wider spread. Its oppositely-arranged, dark green leaves are lighter underneath and are mostly five-lobed, up to 12 inches long, with a coarse, papery texture. Oakleaf hydrangeas exhibit red, orange-brown, to purplish fall color. Its flowers are borne in terminal clusters, called panicles, 10 to 12 inches long. The outer, sterile flowers are showy, starting out white in late spring and summer and turning purplish-pink, then brown in autumn. It produces small, dry capsuled fruit without ornamental qualities.
Use oakleaf hydrangeas in wooded areas, as hedges, in mass plantings, as a specimen or as a foundation plant. As it is a deciduous shrub, losing its leaves in winter, ornamental use is lessened during the colder months.
Oakleaf hydrangeas prefer partial to fairly deep shade locations and nutrient-rich, acidic, well-drained, yet moist, soils. Mulching the root zone aids in water retention in dry soils. Newly planted, young shrubs need winter protection in cold climates. Propagate oakleaf hydrangeas by seed, cuttings, layering or by division.
'Harmony' has large, dense flowers that tend to weigh branches down. 'Snow Queen,' growing to 6 feet tall, is a common commercial cultivar bearing many flowers. 'Snowflake' is very showy with pure white flowers that appear as doubles.
Insect problems of oakleaf hydrangeas include scale and chewing insects, but none are usually serious. Zone 5 temperatures may result in twig death and flower bud injury. Provide winter protection to reduce damage.