How can you tell if a shrub or tree is male or female?

There is no way you can tell if a plant will be male or female when you buy it unless it is in bloom. If it is important that a particular type of plant (like the Ginko) be one or another then buy it from a good nursery. The industry propagates these plants aually from cuttings and what you buy will be whatever the parent was. Some types of plants have both male and female flowers on the same plant and can propagate them selves others have only one type of flower and in order to produce fruit you have to have a male and a female plant close together. I cannot find any information that says dogwoods have separate es or that you should plant a male and female close together.