Just mention the word “hydrangea” and most people immediately think of the mophead and lacecap selections of Hydrangea macrophylla. These glorious shrubs are very popular and commonly found blooming in summer landscapes throughout the country. A less commonly known hydrangea is the oakleaf species (H. quercifolia), which has a different look and feel to it. Like the mopheads and lacecaps, oakleaf hydrangeas also produce large, clusters of very showy flowers. But the similarities between the oakleaf hydrangea and its cousins basically end there.
A number of significant characteristics set the oakleaf hydrangea apart from the other members of the genus.
- Flowering habit – Oakleaf hydrangea flowers appear in elongated, cone-shaped clusters, known as inflorescences (flower heads consisting of a group or cluster of flowers arranged on a stem). The inflorescences consist of a combination of showy sterile and inconspicuous fertile flowers. In contrast, the mophead hydrangeas have globe-shaped clusters of large florets. Lacecap hydrangeas have flattened bloom heads of small female flowers surrounded by larger male flowers.
- Foliage –
Whereas the foliage on H. macrophylla species tends to be moderate sized, ovate or heart shaped, and smooth textured, oakleaf hydrangea foliage is large (4 to 12” long and wide, depending on the selection), lobed, and coarsely textured. Similar in shape to the leaf of an oak tree, the foliage is the inspiration for this shrub’s botanical name, which is derived from the Latin words quercus (oak) and folium (leaf).
- Origin – Most of the 23 recognized hydrangea species belonging to the genus are Asian in origin. Two exceptions, oakleaf hydrangea and smooth hydrangea (H. arborescens), are native to this country. Oakleaf hydrangea is native to all the states in the southeastern quadrant of the United States, from North Carolina south to Florida and west to Louisiana.
- Fall color –
Oakleaf hydrangea is the only member of the genus that provides any significant fall foliage coloration. In November and December, when most other deciduous plants have shed their leaves, the oakleaf hydrangea remains fully clothed in stunning deep red to purple leaves that linger well into winter.
- Cultural requirements – All hydrangeas generally prefer moist, well-drained soil. However, once established, the oakleaf species is able to tolerate drier soil and more sun than other members of the genus.
Oakleaf hydrangea is a deciduous, rounded shrub with a mounding form from the ground up. Strong, sturdy stems hold large clusters of flowers above foliage that is generally dark green on top and whitish green beneath. The stems are an attractive cinnamon or tan color with bark that peels in thin flakes. In the wild, this understory shrub is often found growing in the shade of mixed hardwood trees, along streams, and on forested hillsides. In the cultivated landscape, it is an ornamental plant that grows best in a partially shaded natural or landscaped woodland setting, preferably with morning sun and afternoon shade. It is hardy to zones 6 through 9 with some cultivars hardy to zone 5.
Depending on the cultivar, showy clusters of creamy white or pink flowers bloom on the previous year’s wood. Most cultivars produce single blossoms, but a few produce double blossoms. The blossoms last 4 to 6 weeks or more before aging to either tan or deep pink and are borne in inflorescences measuring 6 to 12 inches long and 3 to 5 inches wide. The flowers dry in place, adding interest to the plant through autumn.
The following list, which is by no means complete, describes a number of oakleaf hydrangea selections and their general sizes and floral displays. While a few cultivars can grow 12 feet or more tall, most cultivars are medium sized, ranging from 5 to 8 feet tall on average. For the gardener with a small garden, many compact selections are available that grow 4 feet tall or less and have proportionately smaller foliage and flower clusters.
- ‘Alice’ – 12’ tall by 12’ wide. This is a good selection for larger gardens that can handle a shrub this size. The large white flowers age to rosy pink before finally turning tan in late summer. ‘Alice’ was the winner of the State Botanical Garden of Georgia gold medal award in the year 2000.
- ‘Alison’ – 8’ to 10’ tall. While similar to ‘Alice’, this cultivar is a little broader and the inflorescences are held more upright than those of ‘Alice’. The large white flower clusters age to pink before turning tan by summer’s end.
- ‘Harmony’ – 10’ tall and wide. This selection exhibits clusters of very large, dense, sterile, double flowers. Their weight can bend down branches. Not often found in nurseries, this selection is uncommonly beautiful, but the weight of the flowers may be a problem.
- ‘Amethyst’ – 6’ tall by 6’ wide. A compact cultivar developed by Dr. Dirr, the flowers turn from white to rose. Both ‘Alice’ and ‘Amethyst’ have very deep pink inflorescences as they age.
- ‘Gatsby Gal’ – 5’ to 6’ tall by 5’ to 6’ wide. This and the following two selections are members of the Gatsby series developed by Proven Winners and introduced in 2016. ‘Gatsby Gal’ has flowers that are upright, making them seem large compared to the compact size of the shrub.
- ‘Gatsby Moon’ – 6’ to 8’ tall by 6’ to 8’ wide. The inflorescences consist of tightly packed, very full double flowers that are reminiscent of those on ‘Harmony’, described above. The flowers age from white to green rather than pink.
- ‘Gatsby Pink’ – 6’ to 8’ tall by 6’ to 8’ wide. The massive, long lasting flower heads rapidly change from white to a rich shade of medium pink.
- ‘Queen of Hearts’ – 6.5’ tall by 9’ wide. The U.S. National Arboretum’s shrub breeding program developed this cultivar from a hybridization of cultivars ‘Snow Queen’ and ‘Pee Wee’, the same cross that also produced ‘Ruby Slippers’ described below. The flowers open white and slowly age to a deep pink color.
- ‘Snow Queen’ – 6’ tall by 6’ wide. ‘Snow Queen’ holds its single-flowered inflorescences more upright than other cultivars and can also handle sunnier sites. It was awarded the Royal Horticultural Society’s Award of Garden Merit in 2012.
- ‘Snowflake’ – 7’ tall by 7’ wide. Another recipient of the Royal Horticultural Society’s Award of Garden Merit in 2012, this cultivar has a longer bloom season than most other cultivars. It sports very long (15 inch) spikes of double hose-in-hose flowers that persist for a long time on the plant. The flowers gradually age to pink and then to light tan.
- ‘Little Honey’ – 4’ tall by 5’ wide. A sport of ‘Pee Wee’, the golden yellow spring foliage gradually darkens to chartreuse green in summer and then turns red in fall. Give it morning sun and afternoon shade for best results. The 5 to 6-inch long, cone-shaped inflorescences of white blooms are small, compared to those of other oakleaf hydrangea species.
- ‘Munchkin’ –
3’ tall by 4.5’ wide. ‘Munchkin was developed by the U.S. National Arboretum’s shrub breeding program in McMinnville, Tennessee. The compact form and dense plant habit make it an ideal choice for small residential landscapes. The flowers open white and gradually turn medium pink.
- ‘Pee Wee’ — 5’ tall by 4’ wide typically but may grow larger. This upright, compact selection holds its rich burgundy and purple leaves very late in the season before dropping them. The leaves average 5” in length and generally have 3 to 7 lobes each. The blossoms age to a tan color in late summer.
- ‘Ruby Slippers’ – 3.5’ tall by 5’ wide. The U.S. National Arboretum’s shrub breeding program developed this mounding, semi-dwarf cultivar from a hybridization of cultivars ‘Snow Queen’ and ‘Pee Wee’. The flowers open white but quickly turn a pale pink shade, which deepens to rosy red later in the summer.
- ‘Sikes Dwarf’ – 2’ to 4’ tall by 3’ to 4’ wide. This compact selection is perfect for smaller gardens and can also be used in a container garden. The flower clusters, which turn light pink as they age, are composed of sterile florets that hide the fertile flowers. ‘Sikes Dwarf’ has an open plant habit and an irregular rounded shape.
Soil – Oakleaf hydrangea prefers moist, organic, fertile, well-drained, slightly acidic soil with a pH of 5.0 – 6.5. Drought tolerant once established, it does appreciate water during very dry conditions. Good drainage is important. Although the plant likes moist soil, it cannot tolerate wet feet.
Sunlight – This shrub can thrive in full to partial shade. However, it performs better with at least a half day or more of sun, which produces a better floral display, stronger stems, and more colorful autumn foliage. Some cultivars can take a sunnier site. Heavy shade, on the other hand, will result in fewer blooms but larger leaves.
Pruning – Oakleaf hydrangea generally requires little if any pruning. Should it become necessary to shape the plant or reduce its size, prune shortly after the shrub flowers. This shrub sets flower buds in late summer for next year. In other words, it blooms on old wood. Pruning at any other time of year will result in the loss of next year’s blossoms.
Pests – Other than occasional damage from spider mites and aphids, insects don’t normally bother this plant. However, deer will nibble on this plant, especially the tender, young spring foliage, so protect the plant with either deer repellent or a physical barrier.
Diseases – Other than leaf spot, this plant is seldom bothered by disease.
Propagation – The shrub may be propagated from stem cuttings. Because the branches are low to the ground, the plant may also be propagated by layering.
USES IN THE LANDSCAPE
Oakleaf hydrangea is a versatile shrub that is bold yet elegant when used as a single specimen; a backdrop to smaller shrubs, bulbs, or perennials; a component of a mixed border; a deciduous hedge; or as a mass planting.
If there’s a downside to oakleaf hydrangeas, it’s that their large, coarsely textured foliage may be off-putting to a timid gardener. Rest assured, the foliage blends very well with daintier-leaved plants. For example, evergreens with their finer needles or scaly branches make a pleasing contrast. The more formal round shape and small, dense leaves of boxwoods contrast well with oakleaf hydrangea’s looser form. Taller ferns, such as ostrich or cinnamon ferns, and shorter grass-like plants, such as liriope, also harmonize well with oakleaf hydrangeas.
Easy-care oakleaf hydrangea offers year-round interest, which makes it especially valuable in the landscape. In the spring, it makes an immediate impact as its bold, handsome foliage emerges. In summer, the large, long-lasting clusters of creamy white or pink flowers contrast with the dark green foliage. Many cultivars gradually mature to medium pink or deep rose. Fall is when the oakleaf hydrangea really makes an impact with its rich, deep burgundy/purple foliage that persists into winter. The dried tan or light brown flower heads add additional interest. In winter, the exfoliating tan bark provides an additional textural element to the snowy landscape.
Dirr’s Hardy Trees and Shrubs, An Illustrated Encyclopedia (Dirr, Michael A., 1997)
“Hydrangea Selection, Pruning and Care,” Virginia Cooperative Extension Publication (ext.vt.edu/chesapeake/programs/anr/Pruning )
”Hydrangeas: Breeding, Selection and Marketing,” Michael Dirr’s Plants Website (dirrplants.com/-hydrangeas)
“Problem-Free Shrubs for Virginia Landscapes,” Virginia Cooperative Extension Publication 450-236 (ext.vt.edu/450/450-236/)
“Selecting Plants for Virginia Landscapes: Showy Flowering Shrubs,” Virginia Cooperative Extension Publication HORT-84P (ext.vt.edu/HORT/HORT-84/)
University of Connecticut College of Agriculture, Health and Natural Resources Plant Database, Hydrangea quercifolia, (hort.uconn.edu)
North Carolina State University Cooperative Extension (plants.ces.ncsu.edu/plants/all/hydrangea-spp)
United States National Arboretum, (usna.usda.gov/Gardens/faqs)
University of Tennessee Hydrangea Production (tnstate.edu/faculty/ablalock/documents/Hydrangea)