(05/17/16) HAMMOND, La. – May is when hydrangeas in Louisiana landscapes begin bursting into flower. Part of our Southern landscape heritage, garden hydrangeas, with their pink or blue flowers, have been around the southeastern United States for 250 years since their introduction from Japan.
“We do, though, have other species of hydrangeas that are native that could be an alternative landscape selection,” said LSU AgCenter horticulturist Allen Owings.
Oakleaf hydrangea, scientifically called Hydrangea quercifolia, is indigenous to the southeastern United States. It grows in nature in mixed hardwood forests, along streams and on forested hillsides, usually on calcareous soils.
“Oakleaf hydrangea is an understory shrub that grows and adapts well in shade provided by oaks, hickories, magnolias and American beech,” Owings said.
Growing to 6 to 10 feet tall, the shrub has deeply lobed, oak-like, 8-inch leaves that turn reddish bronze in fall. The white-flowered panicles start opening in late April through early May in Louisiana and gradually turn pinkish as they age.
Sun and shade are important considerations for planting oakleaf hydrangeas, Owings said. In addition, they spread by stolons and can colonize an area.
Hydrangeas grow best in well-drained soils containing plenty of organic matter. Most species prefer warm, morning sun and cooler, afternoon shade. “Avoid deep shade,” Owings said. “Flower production is better with about five hours of direct sunlight in the morning.”
Oakleaf hydrangea is especially sensitive to saturated soils, and root rot is a common problem in Louisiana. It is caused by poorly drained soils and is common after significant rains. “Even large, established plants may die in this situation,” Owings said.
Owings recommends several oakleaf hydrangea varieties, including Alice, Snowflake and Ellen Huff.
Alice produces creamy white, 10- to 14-inch flower clusters. It tolerates more sun and foliage turns burgundy-red in fall. This selection is from the University of Georgia.
Snowflake is special because of its double sepals that make blooms appear to be double. The florets continue to open throughout summer, giving this variety a longer bloom time than the single-sepal varieties. Plants can grow to be 8-10 feet tall.
Ellen Huff is a strong grower for the Gulf Coast area. “It’s a variety that deserves more use and availability,” Owings said. This variety has good heat tolerance on plants that reach 6-8 feet tall.
New varieties from the U.S. Department of Agriculture are Queen of Hearts, Munchkin and Ruby Slippers. “These have been performing well in the Piney Woods Garden at the AgCenter Hammond Research Station,” Owings said.
Some garden centers sell unnamed oakleaf hydrangea seedlings. “If you find them, try to get those from more southern areas in order to achieve the best success in Louisiana,” he said.
Oakleaf hydrangea success includes obtaining a well-rooted plant, choosing a morning sun-afternoon shade planting location, planting in well-drained soil with a pH of 6.5-7.0 and considering planting in the fall.
“Remember, every landscape in Louisiana may not have an ideal location for this great native,” Owings said. “Following these guidelines, though, will aid in success.”
Early spring flowers of the Ellen Huff oakleaf hydrangea. Photo by Allen Owings
Oakleaf hydrangea flowers in the azalea garden at the LSU AgCenter Hammond Research Station. Photo by Allen Owings