If you are determined to grow dogwood from seed, below is information from an old MDC publication that might help.
Shrub Species Grown at the George O. White Nursery___________________
Dogwood (Cornus spp.)
We grow five species of dogwood, including flowering (C. florida), roughleaf (C. drummondii), red-osier (Cornus sericea), gray
(C. racemosa), and silky (C. oblique) dogwood. The dogwoods are the first seeds we sow in the fall, with a target planting date
of October 1 if possible. Over the years, we have also found that dogwood seeds store very well. Last year we sowed the last
of our 1988 collection of flowering dogwood seeds and we were still getting very good germination and seedling growth. The
reason that we still had 1988 seed available is that I rarely plant all seeds from one source and year. I sow seeds like this with
nearly every species we grow, for both large trees and shrubs. We may plant 100 lb (45 kg) of flowering dogwood seeds in a year,
and these seeds will come from three to five sources from at least that many different years. Much of our flowering dogwood
is locally collected, so the source may be local, but the year collected is different. This helps to avoid total disasters.
Flowering Dogwood—Flowering dogwood is the hardest of the dogwoods to grow, and the seeds are the most expensive.
We get more complaints when we are sold out of this species than about anything else we grow, and we get more complaints
about survival. The seedlings store and outplant poorly. During the growing season, this species is the slowest growing of the
dogwoods, and powdery mildew is a constant problem. About 200 lb (91 kg) of nitrogen (N) are applied each summer to get the
seedlings to 12 in (30 cm) or greater in size, and we treat seedlings with fungicide on a 7- to 10-day schedule. But we sell over
100,000 every year—year in year out—so we keep growing it!
Gray Dogwood—Gray dogwood is not nearly as difficult to grow or handle as flowering dogwood. We have found that it
likewise takes about 200 lb (91 kg) of N per year to get them to 12 in (30 cm) in height. They are faster growing than flowering
dogwood, but not by much. We spray them on the same fungicide schedule as flowering dogwood, but I am not so sure that it
is necessary.
Roughleaf, Red-Osier, and Silky Dogwood—The other three dogwoods are very different than growing flowering and
gray dogwood. These require less than half the nitrogen (N), and all three of these dogwoods usually reach 24 to 36 in (61 to
91 cm) in height with little effort. In addition, they do not require as much or any fungicide as flowering or gray dogwood. All
three species store very well for months in cold storage, and we almost never have any complaints about survival.