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Arboretum Scene

Oxydendrum arboreum
Sourwood, or Sorrel Tree

Branching clusters of seed capsules and fall foliage on a sorrel tree in the Arboretum.

Branching clusters of seed capsules and fall foliage on a sorrel tree in the Arboretum. (Photo by Joy Spurr)

Native to the eastern and southeastern U.S., sourwood is a deciduous understory tree with some wonderful ornamental attributes. In the wild, plants occasionally reach 50 to 70 feet, but here in the Pacific Northwest the tree is relatively slow growing and rarely exceeds 30 feet tall. The tree’s drooping branches bear many finely toothed, lance shaped, glossy green leaves that impart a sour taste when chewed, providing the inspiration for both its common and scientific names (“oxys” is Greek for “acid”).

The small, waxy and fragrant white flowers are held on long, slender, and gracefully curved panicles in early summer, attracting lots of attention from bees. (Honey produced from sourwood trees has a deep, spicy flavor highly prized by connoisseurs.) The flowers develop into persistent, silver-grey fruit capsules that contrast nicely with the foliage’s stunning, crimson-red fall color. Fissured gray bark adds further interest in the winter months.

The only member in its genus, Oxydendrum arboreum belongs to the heath family and along with its ericaceous relatives has a preference for moist, acidic, moderately fertile, and well-drained soils. While it will tolerate much shade, sourwood should be sited where it receives full sun for at least half the day in order to develop good fall color.

In the Arboretum: There are several good specimens in the Rhododendron Glen and even more located in the Woodland Garden.

—Randall Hitchin, Arboretum Foundation