Introduction
A native of the well-drained, upland woods of southeastern North America, Rusty Blackhaw forms a multiple or (occasionally) single-trunked small tree or large shrub, reaching 25 feet in height with an equal spread. The dark bark is blocky, resembling older Flowering Dogwood bark. Trunks usually grow no thicker than six inches and arch away from the tree, forming a pleasing, vase-shaped crown. Leaves are dark green, three inches long, leathery, and extremely glossy. The tree is covered in springtime with striking five-inch-wide clusters of small, white blooms. These flowers are followed by clusters of dark blue, waxy, one-half-inch-long fruits that are extremely popular with wildlife and will occasionally persist on the plant from September throughout the autumn, if not eaten by wildlife. In fall, Rusty Blackhaw puts on a brilliant display of scarlet red to purple foliage.
Credit: Ed Gilman
General Information
Scientific name: Viburnum rufidulum
Pronunciation: vye-BER-num roo-FID-yoo-lum
Common name(s): Rusty Blackhaw, Southern Blackhaw
Family: Caprifoliaceae
USDA hardiness zones: 5B through 9B (Fig. 2)
Origin: native to North America
Uses: sidewalk cutout (tree pit); reclamation; container or planter; street without sidewalk; deck or patio; specimen; hedge; parking lot island < 100 sq ft; parking lot island 100-200 sq ft; parking lot island > 200 sq ft; tree lawn 3-4 feet wide; tree lawn 4-6 feet wide; tree lawn > 6 ft wide; highway median
Availability: somewhat available, may have to go out of the region to find the tree
Description
Height: 20 to 25 feet
Spread: 20 to 25 feet
Crown uniformity: irregular
Crown shape: vase
Crown density: moderate
Growth rate: slow
Texture: medium
Foliage
Leaf arrangement: opposite/subopposite (Fig. 3)
Leaf type: simple
Leaf margin: serrulate
Leaf shape: ovate, obovate
Leaf venation: pinnate
Leaf type and persistence: deciduous
Leaf blade length: 2 to 4 inches
Leaf color: green
Fall color: red, purple
Fall characteristic: showy
Flower
Flower color: white/cream/gray
Flower characteristics: showy
Fruit
Fruit shape: round
Fruit length: less than .5 inch
Fruit covering: fleshy
Fruit color: blue
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 multi-trunked; thorns
Pruning requirement: little required
Breakage: resistant
Current year twig color: brown
Current year twig thickness: thin, medium
Wood specific gravity: unknown
Culture
Light requirement: full sun, partial sun or partial shade, shade tolerant
Soil tolerances: clay; sand; loam; alkaline; acidic; occasionally wet; well-drained
Drought tolerance: high
Aerosol salt tolerance: none
Other
Roots: not a problem
Winter interest: no
Outstanding tree: yes
Invasive potential: little invasive potential
Ozone sensitivity: unknown
Verticillium wilt susceptibility: susceptible
Pest resistance: resistant to pests/diseases
Use and Management
Rusty Blackhaw will grow and look nice in full sun or partial shade on any reasonably fertile, well-drained soil. The tree grows in a shady spot but forms a more open habit. Flowering is significantly reduced in the shade. Although tolerant of drought, it will not tolerate compacted soil. This would be a good tree for planting beneath power lines and in other limited space areas. Useful as a hedge, specimen, or border tree, this deciduous tree adapts well to urban areas. Shoots arise from the root system, sometimes as far out as the dripline. This could be a maintenance problem when planted in a bed of mulch. But sprouts would be routinely cut with regular mowing when planted as a street tree in a lawn. Pests are usually not a major problem.
Propagation is by seed or cuttings.
Pests
This tree is usually pest-free. Viburnum aphid is gray to dark green and feeds in clusters at the tips of the branches, causing leaf curl. Viburnum opulus is especially susceptible. The insects can be dislodged with high pressure water spray from the garden hose.
Inspect the stems of unhealthy-looking plants for possible scale infestations. If found, spray with horticultural oil for some control.
Diseases
Bacterial leafspot causes round, water-soaked spots on leaves and young stems. These develop into shrunken, brown areas about 1/8-inch in diameter. Destroy infected leaves, if you wish. This is not a problem to be concerned about.
Bacterial crown gall forms galls on the lower stems. Do not replant in the same spot.
Shoot blight causes grayish to brown decayed spots on the leaves. The spots first appear at the leaf margins, then spread to the rest of the leaf. Infected flower clusters or twigs are killed.
A number of fungi cause leaf spots. Rake up and destroy infected leaves. These are usually not a serious problem.
Powdery mildew causes a white powdery growth on the leaves, but this Viburnum is usually not affected.
