|Hydrangea arborescens 
Hydrangea arborescens, commonly known as smooth hydrangea, wild hydrangea, or sevenbark, is a species of flowering plant in the family Hydrangeaceae. It is a small- to medium-sized, deciduous shrub up to 3 m (10 ft) tall that is native to the eastern United States.
Smooth hydrangea is widely distributed across the eastern United States—from southern New York to the panhandle of Florida, west to eastern Oklahoma and southeastern Kansas. It is mainly found in moist soils under a hardwood forest canopy and is often common along woodland road banks and streams. It is common in the Delaware River Valley and in the Appalachian Mountains.
At one time both ashy hydrangea (Hydrangea cinerea) and silverleaf hydrangea (Hydrangea radiata) were considered subspecies of smooth hydrangea. However, most taxonomist now consider them to be separate species.
The inflorescence of smooth hydrangea is a corymb. The showy, sterile flowers are usually absent or if present they are usually less than 1 cm in diameter. Flowering occurs May to July. Fruit is a ribbed brown capsule about 2 mm long; many are produced.
The leaves of smooth hydrangea are large (8 to 18 cm long), opposite, serrated, ovate, and deciduous. The lower leaf surface is glabrous or with inconspicuous fine hairs, appearing green; trichomes of the lower surface are restricted to the midrib and major veins.
This attractive native shrub is often cultivated for ornamental use. 'Annabelle' is the best known cultivar of this species; it is one of the most cold hardy of the hydrangeas. The cultivar ‘Grandiflora’ has flowers that resemble snowballs, similar to Viburnum plicatum.
- USDA Natural Resources Conservation Services: Plant Profiles. Hydrangea arborescens L.
- Weakley, Alan S. 2008 (working draft). Flora of Carolinas, Virginia, Georgia, northern Florida, and surrounding areas. University of North Carolina Herbarium.
- Lance, Ron. 2004 Woody Plants of the southeastern United States: A winter guide. The University of Georgia Press. 456 p.
- Purdue University: Horticulture and Landscape Architecture. Smooth Hydrangea.
- McClintock, E. 1957. A monograph of the genus Hydrangea. Proceedings of the California Academy of Sciences 29: 147-256.
- Pilatowski, Ronald E. A taxonomic study of the Hydrangea arborescens complex. Castanea 47: 84-98.
- Missouri Botanical Garden: Hydrangea arborescens.
- Dirr, Michael A. hydrangeas for American gardens. Timber Press. 240 p.
- Mrs. M. Grieve. A Modern Herbal. Hydrangea arborescens.
- Plants for a Future: Hydrangea arborescens .
- Cook, Will. Trees, shrubs, and woody vines of North Carolina. Wild Hydrangea (Hydrangea arborescens).
- Information on cultivar Annabelle
- Hydrangea arborescens Large-format diagnostic photos and information
- Hydrangea Thoughts I - Informative but non-scholarly essay on Hydrangea (Culture, History and Etymology).
- Briartech.com: Smooth Hydrangea, Hydrangea arborescens.