Introduction
This cultivar of Kousa dogwood produces more flowers and fruit than the species and may be more vigorous. It grows 15 to 20 feet tall and has beautiful exfoliating bark, many long-lasting flowers, good fall color, and attractive fruit. Branches grow upright when the tree is young, but appear in horizontal layers on mature trees. The crown eventually grows wider than it is tall on many specimens. It would be difficult to use too many Kousa dogwoods. The white, pointed bracts are produced a month later than flowering dogwood and are effective for about a month, sometimes longer. The red fruits are edible, and they look like a big, round raspberry. Birds devour the fruit quickly. Fall color varies from dull red to maroon.
General Information
Scientific name: Cornus kousa
Pronunciation: KOR-nus KOO-suh
Common name(s): 'Milky Way' kousa dogwood, 'Milky Way' Chinese dogwood, 'Milky Way' Japanese dogwood
Family: Cornaceae
USDA hardiness zones: 5B through 8B (Figure 2)
Origin: not native to North America
Invasive potential: not assessed/incomplete assessment
Uses: specimen; screen; container or planter; deck or patio
Description
Height: 15 to 20 feet
Spread: 15 to 20 feet
Crown uniformity: symmetrical
Crown shape: round
Crown density: dense
Growth rate: slow
Texture: medium
Foliage
Leaf arrangement: opposite/subopposite (Figure 3)
Leaf type: simple
Leaf margin: entire
Leaf shape: ovate
Leaf venation: bowed, pinnate
Leaf type and persistence: deciduous
Leaf blade length: 2 to 4 inches
Leaf color: green
Fall color: purple, red
Fall characteristic: showy
Flower
Flower color: white/cream/gray
Flower characteristics: very showy
Fruit
Fruit shape: oval, round
Fruit length: .5 to 1 inch
Fruit covering: fleshy
Fruit color: red
Fruit characteristics: attracts birds; showy; fruit/leaves not a litter problem
Trunk and Branches
Trunk/bark/branches: branches droop; showy; typically multi-trunked; thorns
Pruning requirement: little required
Breakage: resistant
Current year twig color: brown, green
Current year twig thickness: medium
Wood specific gravity: unknown
Culture
Light requirement: full sun, partial sun, or partial shade
Soil tolerances: sand; loam; clay; 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: resistant
Pest resistance: resistant to pests/diseases
Use and Management
The bark is so attractive on Kousa dogwood that lower branches should be selectively thinned to show it off. Although young trees show only limited bark exfoliation, the tree shows its true bark character as it gets older. The tree also makes a great silhouette as a specimen planting and should be allowed to branch close to the ground to enjoy its full character. The strong horizontal branching habit on older plants is difficult to find in other trees, and it looks great when lit from beneath the canopy. Planting a Kousa dogwood can extend the spring flowering season several weeks since it flowers just after flowering dogwood.
Kousa dogwood should be planted in place of Cornus florida where Discula anthracnose is a problem. It is not rated as an urban tough tree and needs open soil space to look its best. Some shade will improve performance in restricted soil spaces.
Growth is best on moist, loamy, well-drained soil (not heavy clay) with mulch or leaf litter accumulated over the roots. Kousa dogwood is not particularly drought- or heat-tolerant, requiring irrigation during drought periods in summer. It is sensitive to reflected heat, so is not suited to downtown landscapes. Best in some shade in the southern part of its range.
Pests
Several borers will attack dogwood. Try to keep the trees healthy with regular fertilization. Indications of borer problems are holes in the trunk, leaves smaller than normal, and dieback of the crown.
Dogwood club gall midge causes galls at the branch tips. The leaves on affected branch tips may be distorted and the branch may fail to form a flower bud. Prune out the galls as soon as they are seen.
Leaf miners cause brown blister-like mines on the undersides of leaves. The adult leaf miner skeletonizes the leaves.
Scales can build up to large numbers before being detected. Horticultural oil will help control overwintering stages.
Aphids on small trees may be partially removed by spraying them with a strong stream of water from the garden hose.
Diseases
Most of the diseases listed are seen most often on Cornus florida. However other dogwoods are susceptible to the diseases listed.
Early symptoms of dogwood canker are smaller and paler leaves. Leaves on infected branches are red earlier in the fall. At first the symptoms appear only on the infected side of the tree but become more general as the canker enlarges. There is no chemical control for the disease. Avoid trunk wounds during and after planting.
Crown canker is associated with wet soils and can be controlled with appropriate fungicides.
Flower and leaf blight caused by Botrytis cinerea attacks fading bracts, especially during wet weather. Infected flower parts fall on the leaves spreading the infection.
A large number of leaf spots attack dogwood. Clean up and dispose of infected leaves.
Powdery mildew covers the leaves with a fine white coating.
Leaf scorch occurs during hot, dry, windy weather. This condition looks like a disease. Scorch symptoms are drying and browning of the leaf margins, or, in more serious cases, drying and browning of the interveinal area.
