Oxydendrum spp.

sourwood

Ericaceae

Eastern and southeastern United States

Attracts Pollinators Attracts Butterflies Fragrant (light)

Native to North America

SunFull Sun – Part Shade

WaterMedium

HardinessZones 5–9

Overview

Oxydendrum spp. is a genus in the family Ericaceae represented by the single species O. arboreum, the sourwood or sorrel tree, native to the southeastern United States. It forms a deciduous tree 25 to 50 feet (7.5 to 15 m) tall, occasionally reaching 60 feet (18 m), with a slender trunk, rounded to pyramidal crown, and deeply furrowed gray bark. The alternate leaves are 4 to 8 inches (10 to 20 cm) long, oblong to lance-shaped, finely toothed, and carry a sour taste from oxalic acid. In midsummer, small white urn-shaped flowers about 0.3 inch (8 mm) long hang in arching panicles 4 to 10 inches (10 to 25 cm) long at the branch tips. The fruit is a small dry capsule that persists into winter. Foliage turns deep red to maroon in autumn, among the earliest woody plants in its range to color. The tree grows slowly, often adding less than 12 inches (30 cm) of height a year, and reaches flowering size after several years. It requires acidic, well-drained soil and declines on compacted or alkaline ground, which limits its use in disturbed urban sites.

Native Range

Oxydendrum arboreum is native to the eastern and southeastern United States, from Pennsylvania and Ohio south to the Gulf Coast and west to Louisiana. It grows on well-drained slopes, ridges, and woodland margins, often alongside oaks and pines on acidic soils.

Suggested Uses

Sourwood is grown as a specimen tree in lawns and woodland gardens where acidic soil is present. Its summer flowers support honey production, and the autumn foliage extends seasonal color. It is planted along woodland edges and in naturalized settings rather than in compacted street plantings.

How to Identify

Identify by the slender deciduous tree habit with deeply furrowed gray bark and alternate, oblong, finely toothed leaves 4 to 8 inches (10 to 20 cm) long that taste sour. In midsummer, drooping one-sided panicles of small white urn-shaped flowers form at the branch tips. Red to maroon autumn foliage and persistent dry seed capsules confirm the species.

Appearance

Size & Dimensions

Height25' - 50'

Width/Spread20' - 30'

Reaches mature size in approximately 25 years

Colors

Flower Colors

white

Foliage Colors

green

Fall Foliage Colors

red

maroon

purple

Bloom Information

Bloom Period

~4 weeks

Summer

Flowering occurs in mid to late summer, generally June to August, later than most temperate flowering trees. The white urn-shaped flowers open along arching one-sided panicles and draw bees. Dry capsules follow and remain on the branches into winter.

Detailed Descriptions

Foliage Description

green, turning red to maroon in autumn

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-8 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range4.5 - 6.0(Acidic)

357912

Soil Types

loam sand

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

10-15 years to flowering size

Care & Maintenance

Care Guide

Sourwood grows in full sun to part shade on moist, acidic, well-drained soil rich in organic matter. It establishes slowly and is sensitive to root disturbance, so transplanting is done while the tree is young. Growth is intolerant of soil compaction, drought stress, and alkaline conditions, and the species rarely succeeds in polluted urban settings. Once established it needs little supplemental feeding and has few serious pests, though leaf spot can occur in humid summers. A mulch layer over the root zone conserves moisture and moderates soil temperature.

Pruning

Little pruning is required beyond removing dead or crossing branches in late winter while dormant. The naturally upright form develops without training. Old flower panicles need not be removed and break down on their own.