What Is Sourwood?

Sourwood is a deciduous tree with a native range throughout much of the eastern United States. Sourwood is the common name of Oxydendrum arboreum. It is classified in the family Ericaceae, which is also known as the heath family. It is sometimes used as a landscape tree but is also very noticeable in the forest due to its red fall color and white flowers.

History

Oxydendrum arboreum (L.) DC. was first described as a species in 1753 by Linnaeus with the name Andromeda arborea. In 1893, sourwood's scientific name was revised to give us the name we currently use. Sourwood is the only species found in the genus Oxydendrum. Oxydendrum means acid tree or sharp tree, referring to the acidic or sharp taste of the leaves.

Identification

A sourwood tree can reach heights of 30 meters but is more commonly seen at 10 to 12 meters tall. Sourwood is deciduous with leaves that are alternate, oblong and range from 7 to 25 cm in length. The leaves are finely serrated and often have a drooping habit. Sourwood flowers are white and urn-shaped, as is seen in other species within the Ericaceae. The flowers are born on single-sided racemes that are clustered toward the ends of the branches.

Benefits

Sourwood is used as a landscape tree. It is not planted for its form, which is often non-symmetrical and sometimes leaning. It is, however, planted for its white summer flowers and deep red fall foliage color. In addition to its landscape aesthetics, sourwood adds to the beauty of a forest setting because it is one of the first trees to change color in the fall. While not an important timber tree, sourwood is valued for the honey produced from it.

Considerations

Sourwood grows most often on sites with acid soils. It can be found in bottomland hardwood or dry upland habitats. It grows best on moist, well-drained sites and does not seem to tolerate drought or flooding. Drought, excess water and pest stresses can often lead to leaf drop. While Sourwood is most often seen as an understory tree and is shade tolerant, overstory trees can be found, especially in the southern Appalachians.

Misconceptions

Sourwood is sometimes incorrectly described as pest and disease free. Several pests affect sourwood, but not so significantly that it should be avoided in a landscape situation. Examples of insect pests include the dogwood twig borer and fall web worm. Stem cankers and leaf spots sometimes occur on sourwood as well. These pests and diseases are most often found in a forest setting and can sometimes lead to premature leaf drop.

References

• Dirr, A.M. 1998. Manual of Woody Landscape Plants. Stipes Publishing, Champaign. 1187 pp.
• Duncan, W.H. and M.B. Duncan. 2000. Trees of the Southeastern United States. University of Georgia Press, Athens. 322 pp.
• Overton, R. P. 1990. Oxydendrum arboreum (l.) DC.---Sourwood, p. 497--500. In R. M. Burns and B. H. Honkala, [eds.], Silvics of North America, Vol. 2, Hardwoods. Agriculture Handbook 654. U.S. Forest Service, Washington, DC.