One of the most anticipated signs of spring in Portland is our flowering trees. In May, flowering Cherry and Plum trees conclude their reign, making way for our magnificent Dogwoods. Today, May 1, white and pink flowers dot the city, insisting that spring rain gives up and makes room for sunshine.
There is more to Dogwoods than trees though. Cornus, the Dogwood genus hosts tough shrubs and sweet groundcovers that thrive in our climate.
Cornus alternifolia Pagoda Dogwood - Small tree that grows with a tiered habit like a pagoda. Small creamy white flowers in flat clusters bloom in June. Foliage is green and fall color is red to purple. Fruit is blue-black. Cornus alternifolia ‘Argentea’ is a variegated form with white and green leaves that is rare in cultivation. Grows to 15-20’ tall x 15-20’ wide. Likes sun to partial shade. Hardy Z3
Cornus alternifolia ‘Argentea’ is a variegated form with white and green leaves that is rare in cultivation. Grows to 15-20’ tall x 15-20’ wide. Likes sun to partial shade. Hardy Z3
Cornus controversa Giant Dogwood – One of the largest-growing species. Creamy white flowers in clusters bloom in June. Leaves are green with purple fall color. Fruit starts out red and turns black in late summer. Grows fast to 35-45’ tall with horizontal branching habit. Likes sun, part shade & moist soil. Hardy Z5
Cornus florida Eastern Dogwood – Native to eastern US. The most commonly known Dogwood, C. florida has many cultivated varieties. True flowers are small and greenish yellow, surrounded by white or pink bracts which function as flowers. Many cultivars are available.
The pink Dogwoods that bloom around Portland in May are mostly Cornus florida ‘Rubra’ (pictured here). Several cultivars are available that have variegated leaves, adding a decorative aspect to the tree during summer months when flowering is over. Grows slowly to 15-20’ tall with a traditional round shape. Grows best with morning sun and afternoon shade – check cultural requirements.
C. florida is susceptible to anthracnose and other diseases that effect Dogwoods. Please check disease information available on this page. Hardy Z6
Cornus florida x Cornus kousa Stellar series Dogwoods – Bred for excellent flowering of C. florida and disease resistance of C. kousa. White and pink forms are available.
Cornus kousa Korean/Chinese Dogwood – True flowers are small & yellow with showy bracts similar to C. florida but smaller. Flowers bloom in June, after leaves have grown in. Large round fruit is strawberry red and very decorative amongst the red and purple leaves of autumn. Grows slowly to 15-20’. Shape is vase-like in youth, broadening to a multi-level tiered shape when mature. Hardy Z5.
C. kousa is very resistant to many of the diseases effecting Dogwood trees that are native to the US. For that reason it has become the Dogwood of choice for many Portland gardeners.
Cornus kousa x Cornus nuttallii – A new group of hybrids that strive for the best qualities of both parents. Portland Nursery has been fortunate to find two varieties for spring ’08.
Cornus ‘Starlight’ – Favors C. nuttallii with large with flowers before leaves emerge & tall upright growth to 25-30’. Has the disease resistance of C. kousa. Z6
Cornus ‘Venus’ – White flowers in April-May with clean glossy leaves and shrubby habit similar to C. kousa. Grows to 15’ x 20’, Z6
Cornus mas - Cornelian Cherry – Small yellow flowers in late winter before leaves emerge. Leaves are green. The common name comes from the edible fruit that resembles cherries. Bark is rough and interesting texture. Grows to 20-25’ tall, 15’ wide. Best in full sun. Hardy Z4
Cornus nuttallii - Pacific Dogwood – Our native Dogwood tree that blooms with brilliant white flowers in April-May, and often surprises with a second bloom in autumn! Cornus nuttallii is notorious for being difficult to grow in captivity, so it is very hard to find in nurseries. Portland Nursery is able to supply a few small sizes, plus several named cultivars that have been easier for growers to work with.
‘Colrigo Giant’ was found growing near the bridge of the gods in the gorge. It has very large flowers up to 7” across, extra all-around vigor and larger mature size, 45’.
‘Gold Spot’ has white flowers and green leaves with yellow spots.
Leaves are green. Fruit is small & red. Grows fast, to 30-40’ tall with an upright oval shape. Best in partial shade. Hardy Z7.
Shrubs and Perennials
Redtwig Dogwoods make up the most popular Dogwood shrubs. They show off brightly colored decorative bark in winter when many other plants are resting. Twig color varies from dark maroon to coral to yellow depending on species and variety. Most have green leaves with a few variegated forms available. Small white flowers occur in clusters in spring followed by white to blue fruit in late summer.
Generally, Redtwig Dogwoods grow fast to 8-12’ tall & wide with dense branching and foliage. A few lower-growing and dwarf forms are available as well. Most grow very fast, are very tough, adapting to many different soils and light conditions and withstanding temperatures as low as -50 degrees.
Here are some of our favorites.
Cornus alba ‘Ivory Halo’
Cornus sanguineum ‘Midwinter Fire’
Cornus canadensis, our native Bunchberry, is a groundcover that has particular cultural requirements. It needs moist soil, high in organic matter and needs to be watered regularly until established. It prefers full or partial shade. Flowers are dainty and white, blooming in spring. Green leaves emerge in April and die down to the ground after frost. Hardy Z2
Photo credits: Peggy Acott and Oregon State University
Origin: 45-50 species native to Asia, Europe and North America. Several species are native to the Pacific Northwest.
Characteristics: The genus is made up of trees, shrubs and herbaceous plants. Flowers are borne in clusters that are sometimes surrounded by modified leaves called bracts. Often the bracts are confused with flowers as they are brightly colored and showy in spring.
Leaves are opposite except for Cornus alternifolia and Cornus controversa. Variegated leaf-forms exist but most species have medium green leaves that turn red & purple in autumn.
Fruit is 2 seeded and ranges in color from white to pink to red.
Size: Tree-form Dogwoods range in size from 15’ to 35’ tall
Shrub-form Dogwoods range from 12” to 15’ tall
Herbaceous Dogwoods – 3-6” tall forming a mat
Culture: Cultural needs vary widely.
Success with Dogwood trees - Many Dogwood trees grow as under story trees in their native habitats, thriving with filtered sunlight and soil that has built perfect structure after years of leaves and needles dropping and composting on the forest floor. It is rare to find such conditions within city limits.
For best results:
1. Site the tree in a spot that gets sunshine in the morning & shade in the afternoon. Too much shade will inhibit flowering and fall color, too much sun can burn leaves. If you ignore this and choose a spot with full sun, realize that the tree will require more water in summer and may have scorched leaves.
2. Mix compost and EB Stone Sure Start Fertilizer into the soil when planting.
3. Add water even if it’s raining.
4. Add a layer of mulch over the surface of the roots, taking care to leave the trunk clear.
5, During the first year the tree will require regular irrigation. Water deeply for 20-30 minutes, enough to soak the root system. Water infrequently, maybe twice a week when temperatures are in the 80-90 degree range. More if temperatures are hotter, less if it is colder. Soaker hoses and Tree Gators.work well to provide slow-release deep watering. When tree roots are established, they require less irrigation. See Tree Gators
6. Lawn watering that is daily and shallow is not appropriate for establishing healthy root systems in trees.
Diseases: Dogwoods are prone to several fungal diseases. The Oregon State University website has great disease photos and information for treatment.