Identifying characteristics:
This genus contains about 45 species of shrubs, small trees and ground covers.
The leaves of dogwoods are opposite,
except those of the alternate-leafed dogwood
(C. alternifolia) and the giant dogwood (C. controversa).
Dogwood leaves are simple, entire and unlobed, with strongly curved veins
that follow the margin. Fall foliage is red, bronze or purple. Most dogwoods
are grown for the color of the branches and twigs, the fall foliage or for
the attractive fruit rather than for the flowers. The small, non-descript
flowers are produced in terminal clusters
on the previous year's growth and are generally yellowish, greenish or white.
Because flowers are produced in huge quantities, however, they are usually
conspicuous on the plant. The "flowers" of species such as the
flowering dogwood (C. florida)
and the Japanese dogwood (C. kousa) are actually large, white leaf
bracts that attract insects for flower pollination. The fruits
are usually showy, terminal clusters of small, white, blue or red berry-like
drupes, each containing one or two hard stones dispersed by feasting birds.
The leaf scars are conspicuously raised, making it easy to distinguish dogwoods
from maples. Each leaf scar has 3 bundle scars. The terminal bud
is often a large, swollen flower bud, especially conspicuous in the flower-bract
bearing species. The bark of dogwoods
is usually colorful. If grown for twig color, the shrubs need to be pruned
back heavily every second year in March, or cut back to the ground every
5 years.
Similar species:
Ecology:
Distribution: Most dogwoods are native to North America, Europe
and Asia. They are often grown in Iowa as ornamentals and 6 species are
native to the state. The alternate-leafed
dogwood (C. alternifolia) is the largest of Iowa dogwoods, reaching
10 to 25 feet, with a tree-like, tiered growth habit. The gray dogwood (C.
racemosa) is the most common native species in the state. The red-osier
dogwood (C. stolonifera) has attractive, bright red stems and the
rough-leaf dogwood (C. drummondii) is a species more often found
in southern Iowa. The roundleaf dogwood (C. rugosa) has nearly round
leaves and greenish stems. The silky dogwood (C. obliqua) is similar
to the gray dogwood.
Habitat: Dogwoods are mostly easy to cultivate, growing well in
a variety of soils and positions, usually found in moist, fertile soils
at forest edges, along fencerows and as understory plants. Dogwoods are
susceptible to several fungus diseases and pests, including crown canker
or collar rot, anthracnose, powdery mildew and borers. The shrub species
are usually less troubled by pests and diseases than the tree species.
Uses:
Wood: The wood of dogwoods is strong, hard, heavy, fine-grained and
resistant to abrasion. The word "cornu" means "horn,"
referring to the wood of the Cornelian-cherry (C. mas), one of the
first species to be known, which has wood resembling the polished horns
of an ox. Daggers and skewers were made from the hard wood, hence the name
"daggerwood," or "dogwood."
Wildlife: Dogwoods are one of the most important native plants for wildlife. Prolific fruit-bearers, they are appreciated and depended upon by many songbirds and important gamebirds. Thickets form shelter and nesting cover for small mammals and birds, and deer and rabbits eat the twigs and foliage.
Horticulture: This genus of plants has been known since antiquity and is mentioned in the writings of Homer, Theosphrastus and Virgil. Excellent as border shrubs, screening plants and as specimens, dogwoods fill an important niche in urban landscaping. Tree species, especially the alternate-leafed dogwood (C. alternifolia) provide elegant forms and are especially effective in woodland settings.
