Oxydendrum is from the Greek oxys and dendron which mean “sour tree” in reference to the sour-tasting leaves; arboreum means “tree-like.”
Sourwood is named for the sour tasting leaves. Lily-of-the-valley is another name for this tree; the flowers resemble the lily-of-the-valley flowers. Another common name is sorrel tree and refers to plants that have acid-flavored or sour leaves.
COUNTRY OF ORIGIN AND NATIVE HABITAT
Sourwood is found on ridges rising above the banks of streams from the coast of Virginia to North Carolina and in southwestern Pennsylvania, southern Ohio, Indiana, Kentucky, Tennessee; Appalachians to western Florida and the coasts of Mississippi and Louisiana. Trees occur frequently in dry to mesic forests in Kentucky. Sourwood is short-lived rarely exceeding 80 years. There is only one species of sourwood.
Growth Habit and Form
Sourwood is a deciduous narrow tree with rounded top and drooping branches. Trees typically grow up to about 30 feet in height and 20 feet in spread. Sourwood typically develops into a broadly conical tree with branches that droop toward their tips, giving it a graceful appearance.
Leaves are alternate, simple, oblong to lance-shaped and 3 to 8 inches long. Leaf tips taper to a point and leaf margins are minutely toothed. Summer leaves are glossy green. The foliage turns yellow, orange, scarlet, and purple in the fall.
Small, bell-shaped, creamy white, and fragrant flowers are borne in 4 to 10 inch-long, drooping clusters in June and July. The flower clusters are at the end of the branches and resemble tassels. The flowers are attractive to honeybees, and sourwood honey is considered a delicacy.
Fruits are small (1/3 inch-long), dry capsules that occur in drooping clusters. The seeds are less than ¼ inch and pale brown. Fruit ripens in autumn and persists throughout winter.
Young stems are olive-green to rich red. Mature bark is gray to reddish, thick, and deeply furrowed with broad ridges. Sourwood often has a crook in the trunk because it twists and turns trying to seek light through the canopy of other trees.
Wild and Cultivated Varieties
‘Albomarginatum’ has white leaf margins and white marbling.
‘Chaemeleon’ offers an upright conical habit.
‘Mt. Charm’ is a symmetrical grower with early fall color.
Sourwood is an attractive, all season ornamental. Its multi-season interest makes it an excellent specimen for small residential yards, naturalized areas, and patios. Trees are somewhat soil specific and intolerant of pollution and environmental stresses.
Hardy in USDA Zones 5 to 9.
Slow, 14 to 15 feet over a 12 to 15 year period of time.
Culture and Propagation
Trees grow best in moist, well-drained acidic soils in full sun to light shade. Trees are slow growing and sensitive to air pollution, poor drainage, root disturbance, and soil compaction. Sourwood has a deep and fibrous root system and has a reputation for being difficult to transplant or move. It is best grown from small container-grown plants. For best fall color, trees should be planted in full sun. Propagate by fresh seed in moist peat.
Diseases and Insects
Generally free from insects and diseases.
Sourwood trees provide homes and shelter for wildlife.
Minimal attention given appropriate cultural conditions.
TRADITIONAL AND MODERN USES
Native American Cherokee and Catawba used the leaves and bark for a variety of medicinal uses.
Native Americans used the wood for sled runners, cooking tools and firewood.
In the southern Appalachian region one can buy sourwood honey.
Sourwood also makes a wonderful landscape tree. Sourwood was introduced into cultivation in 1747.