Sourwood

Basic Information
Tree ID: 
164
Family: 
Ericaceae
Genus and species: 
Oxydendrum arboreum
Description: 
Hi! My name is Sourwood and I am an American, most likely to be found in the Appalachian Mountains. I am a hard-core dicot with my roots taking hold from mountainous Pennsylvania down to northern Florida. I'm a movie connoisseur, but wood like to branch out and explore different genres. Send me recommendations! As a true American, some of my favorites are Tree Movie, Forrest Gump, and Roots. All recommendations are welcome! Outside of my love for cinema, a fun fact about me is that I belong to the blueberry family! I've come to Yale to turn over a new leaf, but unfortunately this meant leaving my family behind. I can get lonely sometimes, but I love having visitors. To find me, head to Marsh and Farnam Gardens. I'm the handsome redhead on the clearing of the slope, right next to a white bench.
Surveyors: 
Eliana Peyton, Caleb Prempeh, Merit Onyekwere
Location
Area: 
Marsh and Farnam Gardens
Collected Data
Tree shape: 
Narrow oval
Date of tree entry: 
02/08/2024
Height: 
6.81 m
Diameter at breast height: 
0.20 m

Bark
The bark of the sourwood tree is distinctively colored and textured, depending on the tree's location and age. On mature trees, the bark has a reddish-brown or gray color with vertical ridges separating it into thin, scaly plates. The bark has a somewhat rough and furrowed appearance, with the narrow ridges creating a lightly shaggy texture. The reddish tinge and criss-crossing pattern of the ridged bark makes sourwood easy to identify among other hardwood trees in its native eastern North American range.
Twigs & branches
The twigs of the sourwood tree are slender, smooth, and reddish-brown in color when young. As the twigs mature into branches, they develop a gray outer bark with small white lenticels, tissues that allow for gas exchange, dotting the surface. The branches are straight and wide-spreading, forming an arched branching pattern with an oval shape.
Foilage
The sourwood tree has medium-sized leaves that vary from 4 to 8 inches long and 1 to 3 inches wide. Its simple, alternately arranged leaves emerge a bright red color in spring before maturing to a rich green. The leaves are oval/oblong in shape with a glossy upper surface. In fall, the sourwood's leaves turn vibrant shades of red, orange, and purple before dropping. The foliage has a distinctively sour smell when crushed, giving rise to the tree's common name.
Reproductive Structures
Sourwood trees are monoecious, which means an individual tree has flowers with both the pollen-producing male stamens and the seed-producing female pistils in the same flower. This allows a single sourwood tree to self-pollinate and produce fruit/seeds without requiring a separate male or female tree nearby. Sourwood trees produce drooping panicles of small, bell-shaped white flowers in late spring. The flowers have five petals, sculpted stamens, and a single pistil, measuring around 1/4 inch across when fully open. The showy flower clusters are highly fragrant and rich in nectar, attracting a variety of insect pollinators like bees, butterflies, and moths. After successful pollination, the flowers give way to dry, oblong capsular fruits that persist into winter, with each capsule containing numerous tiny seeds.
Fruit
The fruit of the sourwood tree is a dry, oblong capsule that develops after the tree's white flowers are pollinated. These capsular fruits dangle in panicle clusters and are green when immature, turning shades of yellow, orange or reddish-brown as they mature and dry out over summer and into fall. Each capsule splits open along five seams when fully ripe, releasing numerous tiny seeds. The persistent sourwood fruits can remain on the tree through winter until dispersed by wind or wildlife, providing visual interest even after leaf drop.
Seasons
Research
Natural range of distribution: 
Habitat: 
The sourwood tree is native to the eastern United States, found primarily in the Appalachian mountains and Piedmont regions from Pennsylvania down to northern Florida and westward to Arkansas and eastern Texas. It grows best on well-drained, acidic soils in upland areas and dry rocky ridges and slopes. Sourwoods are shade-tolerant and often found as understory trees in mixed hardwood forests dominated by oaks, hickories, and other hardwoods. However, they can also thrive in old fields and forest edges receiving plenty of sunlight.
Origin, history, and uses: 
The sourwood’s origins and longest history of use trace back to Native American tribes like the Cherokee, who utilized the tree’s sour-tasting leaves and branches to flavor meat and as an ingredient in traditional beverages. Early European settlers also recognized the sourwood’s culinary and medicinal properties. The tree gets its common name from the distinctively acidic or sour taste when the leaves, twigs, or fruits are chewed. Beyond food uses, sourwood was prized by early settlers for its hard, dense wood ideal for toolhandles, furniture, and other wood products. Today, it remains a popular ornamental landscape tree valued for its four-season visual interest with unique bark, brilliant fall colors, and showy flower clusters. The nectar-rich blossoms are also an excellent source of honey for beekeepers in the tree’s native range. While no longer commonly harvested, the sourwood still holds ethnobotanical value from its long history of use by Native Americans and early European Americans.
 
In terms of modern uses, sourwood lumber is occasionally employed for flooring, veneer, and turned wood products where its unique reddish color and tight grain patterns are desirable. However, the relatively small size of the tree limits its mainstream availability as a commercial timber species. Its primary modern usage remains as an ornamental shade tree providing landscape interest through foliage, flowers, winter branch patterns and bark appearance.
Phenology: 
In early spring, the sourwood's reddish-brown buds begin to swell into bright red new foliage. The glossy green leaves mature through late spring as the showy white flower panicles bloom in late May to June, attracting pollinators. After flowering, the capsular fruits develop over summer, gradually changing from green to yellow to reddish-brown hues before dispersing seeds in fall. The sourwood's fall color display is a highlight, with the leaves turning vibrant shades of red, purple, and orange before dropping. In winter, the tree is bare, revealing the distinctively ridged reddish-brown bark and architectural branch patterns. Leaf emergence renews the cycle the following spring. The phenological timing can vary across the sourwood's native range based on latitude and elevation, but the tree consistently displays multi-season ornamental interest through its foliage, flowers, fruits, and bark characteristics.
References: 

Dirr, Michael A. Manual of Woody Landscape Plants: Their Identification, Ornamental Characteristics, Culture, Propagation and Uses. Stipes Publishing, 2009.

Missouri Botanical Garden. “Sourwood.” Missouri Botanical Garden Plant Finder, 2022, www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=277135.

“Native Plant Profile: Sourwood.” Lady Bird Johnson Wildflower Center, University of Texas at Austin, 2022, www.wildflower.org/plants/result.php?id_plant=oxar.

“Oxydendrum arboreum.” Plant Database, University of Connecticut, 2022, hort.uconn.edu/detail.php?pid=417.

“Sourwood Tree Facts.” Virginia Tech Dendrology, 2022, dendro.cnre.vt.edu/dendropedia/trees/sourwood.cfm.

USDA NRCS National Plant Data Center. “Oxydendrum arboreum.” The PLANTS Database, plants.usda.gov/home/plantProfile?symbol=OXAR. Accessed 22 Apr. 2024.

Comments

Merit Onyekwere on April 23, 2024: