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Publication #ENH-588

Oxydendrum arboreum: Sourwood1

Edward F. Gilman and Dennis G. Watson2

Introduction

Sourwood usually grows as a pyramid or narrow oval with a more or less straight trunk at a height of 25 to 35 feet but can reach 50 to 60 feet tall with a spread of 25 to 30 feet. Occasionally young specimens have a more open spreading habit reminiscent of Redbud. Leaves are dark, lustrous green and appear to weep or hang from the twigs. Branches droop toward the ground forming a graceful outline when planted as a single specimen. The branching pattern and persistent fruit make the tree interesting in the winter. The mid- to late-summer flowers are borne in terminal clusters of racemes which curve upward, creating a graceful effect at flowering time. The fall color is a striking red and orange which is rivaled by only a few other trees such as Blackgum, Chinese Pistache, the pears, and Chinese Tallowtree. There are few sights that are as striking as a row of Sourwood in fall color.

Figure 1. 

Middle-aged Oxydendrum arboreum: Sourwood


Credit:

Ed Gilman


[Click thumbnail to enlarge.]

General Information

Scientific name: Oxydendrum arboreum
Pronunciation: ock-sih-DEN-drum ar-BORE-ee-um
Common name(s): Sourwood, Sorrel-Tree
Family: Ericaceae
USDA hardiness zones: 5A through 9A (Fig. 2)
Origin: native to North America
Invasive potential: little invasive potential
Uses: specimen; highway median; shade
Availability: somewhat available, may have to go out of the region to find the tree

Figure 2. 

Range


[Click thumbnail to enlarge.]

Description

Height: 40 to 60 feet
Spread: 25 to 30 feet
Crown uniformity: irregular
Crown shape: pyramidal, oval
Crown density: dense
Growth rate: slow
Texture: medium

Foliage

Leaf arrangement: alternate (Fig. 3)
Leaf type: simple
Leaf margin: serrulate, entire, undulate
Leaf shape: oblong, lanceolate
Leaf venation: pinnate, brachidodrome
Leaf type and persistence: deciduous
Leaf blade length: 4 to 8 inches
Leaf color: green
Fall color: red, orange
Fall characteristic: showy

Figure 3. 

Foliage


[Click thumbnail to enlarge.]

Flower

Flower color: white/cream/gray
Flower characteristics: showy

Fruit

Fruit shape: oval
Fruit length: less than .5 inch
Fruit covering: dry or hard
Fruit color: brown
Fruit characteristics: does not attract wildlife; not showy; fruit/leaves not a litter problem

Trunk and Branches

Trunk/bark/branches: branches droop; not showy; typically one trunk; thorns
Pruning requirement: little required
Breakage: resistant
Current year twig color: green, reddish
Current year twig thickness: thin, medium
Wood specific gravity: unknown

Culture

Light requirement: full sun, partial sun or partial shade
Soil tolerances: clay; sand; loam; acidic; well-drained
Drought tolerance: moderate
Aerosol salt tolerance: moderate

Other

Roots: not a problem
Winter interest: yes
Outstanding tree: yes
Ozone sensitivity: unknown
Verticillium wilt susceptibility: unknown
Pest resistance: resistant to pests/diseases

Use and Management

The tree grows slowly, adapts to sun or shade, and prefers a slightly acid, peaty loam. The tree transplants easily when young and from containers of any size. Sourwood grows well in confined soil spaces with good drainage making it a candidate for urban plantings but is largely untried as a street tree. It is reportedly sensitive to air pollution injury. Irrigation is required during hot, dry weather to keep leaves on the tree. Reportedly not highly drought-tolerant, but there are beautiful specimens in USDA hardiness zone 7 growing in the open sun in poor clay with no irrigation.

Pests

Pests are usually not a problem for Sourwood. Fall webworm can defoliate portions of the tree in summer and fall but usually control is not needed.

Diseases

Twig blight kills leaves at the branch tips. Trees in poor health seem to be more susceptible. Prune out infected branch tips and fertilize. Leaf spots can discolor some leaves but are not serious other than causing premature defoliation.

Footnotes

1.

This document is ENH-588, one of a series of the Environmental Horticulture, UF/IFAS Extension. Original publication date November 1993. Revised December 2006. Reviewed February 2014. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Edward F. Gilman, professor, Environmental Horticulture Department; Dennis G. Watson, former associate professor, Agricultural Engineering Department, UF/IFAS Extension, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.