Sexual reproduction: These dogwoods probably reach sexual maturity in three to four years. There is one viable seed per drupe in all four species (Stephens 1973).
Seed dispersal: Seeds are dispersed by a variety of birds, including crows, vireos, redheaded woodpeckers and bluebirds (Ridley 1930), autumn through winter (Stephens 1973). Availability of perching sites may be important in dispersal.
Germination: Germination usually occurs in the spring following seed production and dispersal to a favorable site, but may be delayed a year due to a dormant embryo, hard pericarp (Brinkman 1974), and possible chemical inhibition by the pulp (Goodwin 1948). Mechanical and chemical scarification and stratification techniques are used commercially to stimulate germination in dogwood (Brinkman 1974). C. racemosa and C. stolonifera are described by Krefting and Roe (1949) as having "double dormancy", or requiring two periods of stratification for germination. C. stolonifera seeds that were treated first with acids then with cold stratification experienced almost 100% germination, whereas germination was much lower for those seeds receiving cold treatment only. However, seeds of both species that were twice stratified by passage through quail or pheasant gut plus cold treatment also gave relatively low percent germination. The authors suggested that this was due to a large amount of variability in the extent of scarification from the bird gizzards. Some seeds are injured or overstratified in the bird gut and some are left unscathed or understratified (Krefting and Roe 1949).
Seedling establishment: Some Cornus spp. shrub seedlings are tolerant of variable light intensities, and may become established in woodland edges, within woods, or in open areas (Gatherum et al. 1963, Smith 1975). Seedlings may invade grasslands alone or with other woody plants (McClain pers. comm.).
Asexual reproduction: C. drummondii, C. racemosa, C. stolonifera and C. obliqua reproduce most successfully by vegetative growth following seedling establishment. Thickets may expand by adventitious underground shoot growth or rhizomatous growth (Stephens 1973, Wilson 1965, Smith 1975).
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