When the Kousa Dogwoods Bloom the Northwest Takes Notice

The world takes notice when the Kousa dogwoods bloom from May to June. This region needs to turn away from the popular, prone-to-disease, ornamental cherry trees and turn to some great trees Cornus kousa. Imagine walking down a dogwood-lined street when these cultivated species are in bloom. It would be a horticulture dreamscape, turning a neighborhood or town into a floral wonderland for three to four weeks out of the year.

Considered by enthusiasts as one of the most desirable trees for Western gardens, Kousa dogwood provides four seasons of interest in the landscape. Its cultivars have some of the most prominent bracts and fruit in the genus. Its dark-green leaves with wavy margins are easy to identify as dogwood. The foliage carries the plant through summer, providing shade during the dog days of summer. Yet, the beauty does not stop once the flowers fade.

The dogwood gives another seasonal show in autumn, when the leaves turn a glorious, deep crimson to purple and the strawberry-red fruit dangles from the branches. Once the leaves and fruits fall, it is the bark’s turn to show off its mottled, exfoliating, tan-and-gray bark.

In the history of the Earth, the genus Cornus has been around for a long time, dating back to when dinosaurs ruled the world. Many species in the genus populated the Northern Hemisphere, and C. kousa grew in Korea, China, and Japan.

The name Cornus comes from the Latin word cornu, which means horn. Some acknowledge that the name is a tribute to the density and strength of the wood. The epithet kousa is the Japanese word for dogwood.

The common name dogwood has nothing to do with dogs. Europeans originally called the plants whippletrees, which evolved into dog trees and eventually dogwood. Some language experts believe the common name is attributed to a misspelling of dagwood — primitive weapons such as darts and arrow shafts made from a hardwood called dags.
Crosses with other species produced many fine garden-worthy specimens. The species will reach 20 to 30 feet and 15 to 30 feet wide, although some cultivars are smaller in stature.

“It is always encouraging to find one’s plants reproducing themselves naturally, as it shows they made themselves at home,” British gardener Norman Hadden once said. Growing our native Pacific dogwood, Cornus nuttallii, he spotted a seedling growing under it in his English garden in the late 1950s. Hadden speculated the small plant was a cross of C. nuttallii and a C. kousa that grew nearby. The semi-evergreen shrub bloomed profusely in early summer, with star-shaped flowers opening white and maturing pink. The shrub covered itself in red fruits in the fall.

In 1968, the tree was exhibited under the name Cornus ‘Porlock.’ Meanwhile, Hadden found another notable seedling, which later showed as ‘Norman Hadden.’ Both trees were similar, making botanists question their origins. Neither variety came from the Northwest native dogwood as once thought. Both varieties’ parentage came from C. capitata and C. kousa.

Besides the common name kousa dogwood, the tree goes by Chinese dogwood, Japanese dogwood, Korean dogwood, strawberry tree and yang-mei (Chinese).

Cornus kousa is a dweller of moist, fertile forests, yet it will grow in full sun to partial shade. In a garden setting, they will thrive in humus-rich, moist, well-drained, fertile soil with an acidic to neutral pH.

Propagate the species by sowing seeds in an outdoor seedbed in autumn. Root the softwood cuttings in summer and hardwood cuttings in autumn.

Diseases

Cornus kousa is relatively free of disease. The Asian dogwood is spared from outbreaks of Discula spp., an organism responsible for the dreaded dogwood anthracnose. The disease plagues the Northwest native C. nuttallii and East Coast native C. florida.

Except for Cornus kousa var chinensis, which is highly susceptible to the disease, C. kousa has few outbreaks. The disease remains as foliar lesions, which do not kill the species’ cultivars.

Pruning

Because dogwood trees throw water sprouts easily, pruning is a tricky business. Prune too much, and your tree will grow numerous water sprouts from each cut. When planning your garden, place your tree where it can reach its full potential size without pruning.

Noteworthy Crosses and Cultivars

• Rutger University bred some noteworthy crosses with Cornus kousa and C. florida that are disease-free as well as handsome specimens — Cornus x ‘Rutban’ (sold under trademark Aurora™), C. x ‘Rutdan’ (Celestial™ or Galaxy™), C. x ‘Rutcan’ (Constellation™), C. x ‘Rutlan’ (Ruth Ellen™), C. x ‘Rutfan’ (Stardust™), C. x ‘Rutgan’ (Stellar Pink™).
• ‘Little Poncho’ is a dwarf kousa that reaches 8-10 feet tall, a choice alternative for small gardens.
• ‘Milky Way,’ a popular cultivar with a broad bushy form, produces many flowers in the spring, followed by fruit later in the growing season.
• ‘Wolf Eye’ is a variegated cultivar with green leaves, creamy-white, wavy margins, and pink-to-red autumn color. Grow this for the beautiful foliage and flowers, with a small stature of 6 feet tall and wide.
• ‘Beni Fuji,’ with narrow red bracts, has the darkest hue of all the kousa cultivars.
• ‘Moonbeam’ has large, drooping bracts.
• ‘Big Apple’ is a large, spreading tree. The fruits are 1-1/4 to 1-1/2 inches across, and the bracts are up to 5 inches across.
• ‘Radiant Rose’ is beautiful with pink flower bracts, red-tinted summer leaves and red fall leaves.
• ‘Miss Satomi’ is a spreading shrub, sometimes sold as ‘Satomi.’ Deep-pink bracts surround the flowers, followed by rosy-pink fruit. Leaves turn rose-pink and purple in autumn.

Originally written for the May/June 2018 edition of West Sound Magazine.