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How to Manage and Identify Sourwood

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Sourwood in Fall

Sourwood in Fall

Virginia Tech Dedrology

Introduction:

Sourwood leaves are dark, lustrous green and appear to weep or hang from the twigs while branches droop toward the ground. Branching patterns and persistent fruit make the tree interesting in the winter.
Sourwood is one of the first trees to turn colors in the Eastern forest. By late August it is common to see foliage of young sourwood trees along roadsides beginning to turn red. The fall color of sourwood is a striking red and orange and associated with blackgum and sassifras.

Specifics:

Scientific name: Oxydendrum arboreum
Pronunciation: ock-sih-DEN-drum ar-BORE-ee-um
Common name(s): Sourwood, Sorrel-Tree
Family: Ericaceae
USDA hardiness zones: USDA hardiness zones: USDA hardiness zones: 5 through 9A
Origin: native to North America
Uses: recommended for buffer strips around parking lots or for median strip plantings in the highway; shade tree; specimen; no proven urban tolerance Availability: somewhat available, may have to go out of the region to find the tree

Special Uses:

Sourwood is occasionally used as an ornamental because of its brilliant fall color and midsummer flowers. It is of little value as a timber species but the wood is heavy and is used locally for handles, firewood and in mixture with other species for pulp. Sourwood is important as a source of honey in some areas and sourwood honey is marketed locally.

Description:

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.
Crown density: dense
Growth rate: slow
Texture: medium

Leaves:

Leaf arrangement: alternate
Leaf type: simple
Leaf margin: entire; serrulate; undulate
Leaf shape: lanceolate; oblong
Leaf venation: banchidodrome; pinnate
Leaf type and persistence: deciduous
Leaf blade length: 4 to 8 inches
Leaf color: green Fall color: orange; red Fall characteristic: showy

Trunk and Branches:

Trunk/bark/branches: droop as the tree grows, and will require pruning for vehicular or pedestrian clearance beneath the canopy; not particularly showy; should be grown with a single leader; no thorns
Pruning requirement: needs little pruning to develop a strong structure
Breakage: resistant
Current year twig color: green; reddish
Current year twig thickness: medium; thin

Pests and Diseases:

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.

Culture:

Light requirement: tree grows in part shade/part sun; tree grows in full sun
Soil tolerances: clay; loam; sand; acidic; well-drained
Drought tolerance: moderate
Aerosol salt tolerance: moderate

In Depth:

Sourwood 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.

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