Sourwood, or Sorrel, Trees
Oxydendrum arboreum, also called sourwood, lily of the valley or sorrel, is a deciduous tree species native to ravines, bluffs and clearings in the southeastern United States. Sourwood trees have minimal value as a commercial timber species, according to the U.S. Forest Service, but homeowners and growers prize them as ornamentals because they produce attractive blossoms and showy fall foliage. They work well as specimen trees, on patios or in naturalistic settings. Does this Spark an idea?
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Identification
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Cultivated sourwood trees grow between 20 and 30 feet high with a 10- to 15-foot spread but can reach heights between 50 and 75 feet in the wild. They have grayish-brown bark and narrow, pyramidal or rounded crowns with pendulous branches. Their oval-shaped alternating leaves are glossy and deep green with pointed tips. Drooping clusters of sweet-smelling, urn-shaped white blossoms emerge in mid-summer. Small brownish seed capsules replace the showy blossoms. The leaves change to vivid shades of purple, maroon or red in autumn.
Cultivation
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Sourwood trees are hardy in U.S. Department of Agriculture hardiness zones 6 through 9. They can tolerate temperatures between 105 degrees F and -15 degrees F. Sourwoods have a slow growth rate. Although shade tolerant, they produce more flowers and better fall color if they grow in full sunlight, according to the University of Connecticut. They prefer acidic soils with pH levels ranging between 3.7 and 6.5, and grow best in well-drained, moist, peaty soil.
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History
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Native Americans used sourwood for thousands of years before European settlers arrived in North America. They chewed the gum to treat mouth ulcers and relieve thirst, and soothed irritated skin with the tree sap. They treated respiratory, intestinal and female problems with leaf infusions, and used other parts of the tree as a diuretic. Early European colonists brewed sourwood to create beverages and treated cardiac and urinary problems with sourwood tonics. They also created arrow shafts, machine parts and tool handles from sourwood timber.
Liabilities
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Sourwood trees are generally free from serious diseases and pest problems. Regal moth larvae occasionally eat sourwood foliage, while twig girdlers and borers burrow inside the twigs. Recently transplanted or immature trees may be somewhat less cold-hardy than older or established trees, and trees may suffer from twig dieback during the winter months. Sourwoods have shallow root systems and are often difficult to transplant. They do not work well as park or urban trees and are intolerant of pollution.
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