Dogwood trees (Cornus spp.) are loved for their architectural branches that are covered in white or pink bracts around their tiny light green true flowers. Two species are most widely encountered in gardens, the flowering dogwood (Cornus florida) that blooms in mid-spring, and the kousa dogwood (Cornus kousa) which blooms later in early to mid-summer when its foliage is present.
Where Dogwoods Grow
Dogwood trees grow in temperate climate regions where temperatures in winter are no lower than -10 to -20 degrees Fahrenheit but chilly enough, below 45 degrees, to induce flowering. Flowering dogwood (Cornus florida) is a forest understory tree from the eastern United States that tolerates full sun exposures in cooler climates but performs better if grown in partial sun to partial shade, receiving no more than four to six hours of direct sunlight daily. Kousa dogwood (Cornus kousa) grows in soils that are less acidic or moist than that of the flowering dogwood. This species is native to eastern Asia and attains its finest shape and flowering if grown in full sun, a minimum of six to eight hours of direct sunlight daily.
Dogwoods flower in spring or summer, depending on species and climate. Flowering dogwood (Cornus florida) blooms in mid-spring before leaves emerge, which ranges from March in northern Florida to early May near the Canadian border. Kousa dogwood (Cornus kousa) blooms later when the foliage is fully present and mature in very early summer to mid-summer. For example, in the American South it flowers in May, while in the Northeast it blooms in June and July.
Dogwood tree flowers are comprised of two main components. The true flowers are in the middle of the "blossom." They are small, pale green or chartreuse yellow and easily overlooked, if not simply mundane. Surrounding the flowers are four bracts, or colored modified leaves, that most assume to be the dogwood flower. These bracts are first pale green and then mature to shades of white, cream, pale pink or rose.
Although the true tiny flowers might endure for only a week, the showy bracts persist for much longer, adding to the ornamental appeal of dogwood trees in the garden.
Dogwood trees are among the most regarded flowering trees. Their table-like or tabular branching forms are loved to soften the vertical trunks of taller trees in woodland groves as well as to provide architectural beauty in a mixed border or as a singular specimen in a lawn. The flowering season is the crowning glory, adding beauty and value to a property.
Because the bracts are long-lasting, the flowering dogwood in particular has earned favor as a seasonal cut flower. It is the state flower of Virginia and North Carolina.
Variations and Selections
Flowering dogwood trees are susceptible to the disease anthracnose, and much plant breeding has lead to many new varieties with disease resistances and increased flower bract colors or forms. Cultivars 'Rubra', 'Cherokee Pink' and 'Cherokee Chief' have pink bracts while 'Pluribracteata' has white bracts in numerous rows, a double form, that makes the blossom look like that of a magnolia. Both 'Cherokee Sunset' and 'Red Cloud' have nearly red bracts, best described as magenta-pink.
Kousa dogwood flowers are always white, but variations in the size or shape of the white bracts adds interest among cultivars.
Hybrid crosses have been made between flowering dogwood and kousa dogwood. These trees have excellent disease resistance, are more adaptable to slightly drier growing conditions and have flower bracts of white, pink and striped combinations with different bract shapes.