Many hydrangea species and cultivars offer the ubiquitous white, pink or blue flower globes on mounds of deep-green foliage. Oakleaf (Hydrangea quercifolia) stands apart from other species in both looks and habits. A native American species, oakleaf thrives in U.S. Department of Agriculture plant hardiness zones 5 though 9. To grow this shrub in full sun, you'll need to make accommodations in its culture.
While the leaves of other hydrangea species are round or oval, oakleaf foliage is deeply lobed like that of an oak leaf. Additionally, unlike the vast majority of hydrangea foliage, oakleaf's leaves turn a deep maroon in the autumn. The plant can grow to 8 feet high and equally wide. It produces pyramidal clusters of white flowers in early summer that mature to shades of pink in autumn. The more direct sun the plant receives, the more the flower tones fade.
Most hydrangea species like sun, but not all day, every day. Experts at the United States National Arboretum recommend planting hydrangeas where they get full sun in the morning and some shade in the afternoon. Alternatively, plant shrubs where they get dappled sunlight all day long. Oakleafs, native to woodlands in the southeastern part of the United States, also prefer filtered sun or shade during the hottest part of the day. However, like other hydrangeas, the amount of sun they tolerate depends on the cultivar, the climate and the water available. The farther north, the more sun your oakleaf can tolerate, but you must compensate with generous irrigation.
If you grow oakleaf in full sun, it's worth your while to apply a good layer of organic mulch. Mulch is any material that you place on the soil over the roots of a plant to protect it from temperature fluctuations, keep down weeds and lock in humidity. Organic mulches such as compost or chopped, dried leaves also disintegrate into the soil and make it more fertile. For best results with a full-sun oakleaf, plant it in deep, well-drained soil and add a 3-inch layer of organic mulch across its entire root area, keeping it several inches away from plant foliage. You still need to irrigate regularly and generously in summer heat, but the mulch locks in the humidity and helps keep the oakleaf's roots cool.
The species that can take the most direct sun with the least concern is panicle hydrangea (Hydrangea paniculata) that thrives in USDA zones 3 though 8. Panicle hydrangea blossoms resemble those of oakleaf, growing in elongated white panicles that turn toward pink or lilac with age. However, panicle produces buds on new wood, while oakleaf sets buds on old wood; while oakleaf starts blooming in the beginning of summer, panicle doesn't get going until mid-summer and continues offering flowers through September.
- The United States National Arboretum: Hydrangea Questions and Answers
- Missouri Botanical Garden: Hydrangea Quercifolia
- Missouri Botanical Garden: Hydrangea Quercifolia "Pee Wee"
- Missouri Botanical Garden: Hydrangea Paniculata
- Lady Bird Johnson Wildflower Center: Hydrangea Quercifolia (Oakleaf Hydrangea)
- Monrovia: Penny Mac Hydrangea
- San Marcos Growers: Hydrangea Quercifolia "Snow Queen" - Oakleaf Hydrangea
- ANewsCafe: Humidity-Loving and High-Drama Hydrangeas with Daran Goodsell, Chico
- Lady Bird Johnson Wildflower Center: Ask Mr. Smarty Plants: Leaf Burn on Hydrangeas
- Jupiterimages/Photos.com/Getty Images