Taken from wikipedia's page at:
http://en.wikipedia.org/wiki/C...
"Dogwoods have simple, untoothed leaves with the veins curving distinctively as they approach the leaf margins. Most dogwood species have opposite leaves, while a few, such as Cornus alternifolia and C. controversa, have their leaves alternate. Dogwood flowers have four parts. In many species, the flowers are borne separately in open (but often dense) clusters, while in various other species (such as the flowering dogwood), the flowers themselves are tightly clustered, lacking showy petals, but surrounded by four to six large, typically white petal-like bracts.
Various species of Cornus, particularly the flowering dogwood (Cornus florida), are ubiquitous in American gardens and landscaping; horticulturist Donald Wyman stated "There is a dogwood for almost every part of the U.S. except the hottest and dryest areas."