Among native American deciduous trees suited to general cultivation, Cornus alternifolia, the pagoda dogwood, is rarely encountered in our gardens and nurseries. As is often the case with plants that occur naturally in our own backyards, this exceptional small tree is more widely available in Europe than at home. It deserves greater appreciation.
The dogwoods, members of the genus Cornus, comprise a large assemblage of evergreen and deciduous trees and shrubs native to both the New and Old World. As its specific epithet indicates, Cornus alternifolia (like its Asiatic counterpart, C. controversa) sports leaves in alternate fashion along the stems; the leaves of all other Cornus species are paired and opposite. Though this fact may seem purely academic, learning the leaf arrangements of major plant genera is a useful identification tool.
Native to 36 of the 50 states and the eastern provinces of Canada (primarily east of the Mississippi), C. alternifolia has acquired numerous common names, including pigeonberry, blue pagoda, green osier, and umbrella dogwood. With a natural range that encompasses the brutal climates of the upper Midwest, pagoda dogwood (at least in its northernmost populations) can be considered hardy to USDA Zone 3.
Unlike the so-called flowering dogwoods—C. florida, C. kousa, and C. nuttallii—the pagoda dogwood does not possess large petal-like bracts that surround the flower heads. Instead, flattened disks of small, creamy white flowers, to three inches across, are produced from late spring to early summer. Later, pretty clusters of small, purplish black drupes ripen as the flower stems turn a handsome pinkish red.
Though the flowers are indeed ornamental, the tree's most sensational characteristic is the way the flowers are presented along a strikingly horizontal pattern of branches. This wedding-cake-like growth habit is distinctive in both summer and winter. The younger branches intensify to a rich dusky purple in winter, providing a bold outline in the garden, especially if planted in front of a golden-foliaged conifer. Ultimately, C. alternifolia rises to 25 feet high by 25 feet wide.
Though the flowers, architecture, and winter twig color of C. alternifolia justify its inclusion in any garden, the variegated forms provide an extra measure of summer interest. Cornus alternifolia ‘Argentea’, with a creamy white-margined leaf blade, is the better known, having been introduced into cultivation in the late 19th century by the American nursery of Temple and Beard. Though it has been hugely popular in Europe for decades, it is infrequently found in North American nurseries. A more recent introduction, C. alternifolia ‘Golden Shadows’, appeared as a branch mutation in a private garden in Illinois. It sports exceptionally wide yellow leaf margins.
Cornus alternifolia is found in deep, moist soils in deciduous woodlands and along stream margins and it is, generally speaking, under such garden conditions that it will thrive. The variegated leaf forms are particularly effective in shaded woodland positions.
Propagating C. alternifolia presents little challenge, as seed is abundantly produced and easily germinated. Because of its wide geographical range, seedlings from local populations should be produced for regional use. Unfortunately, propagation of the variegated clones is more problematic. Summer softwood cuttings root readily under mist, but usually fail to break bud the following spring. European nurserymen have overcome this problem by keeping the rooted cuttings in active growth in their cutting flats until spring. Grafting variegated scions onto C. alternifolia rootstock is probably a more dependable—if more cumbersome—approach.
I don't believe that native plants are necessarily better suited to North American gardens than exotics. I do feel, however, that exceptional native species that have been overlooked deserve greater recognition. The pagoda dogwood offers multiseasonal appeal combined with a wide geographical potential, and should be celebrated and planted by more American gardeners. H
TYPE OF PLANT: deciduous shrub or small tree
FAMILY: Cornaceae (dogwood family)
RANGE: eastern Canada to Minnesota; south to Georgia and Alabama
HARDINESS: USDA Zones 3–7; Sunset Zones 1–6, 32–43
HEIGHT/SPREAD: 15–25 ft./15–30 ft.
GROWTH RATE: Slow to moderate
LEAVES: Alternate, simple, oval to ovate, arcuate venation, 2 1/2 to 5 in. long; maroon to reddish purple fall color
FLOWERS: Greenish white, in flattopped clusters, appearing May-June; fragrant
FRUITS: Bluish-black drupes (3/8 in. diameter) in clusters, ripen in August-September
CULTIVARS: ‘Argentea’, with ivory leaf margins; ‘Golden Shadows’, with wide yellow leaf margins
SITE REQUIREMENTS: Sun to partial shade; tolerates a range of soil types but prefers moist, well-drained soil
PROPAGATION: by seed; variegated forms by grafting
COMMENTS: relatively disease resistant; fibrous, spreading root system; keep root zone cool