The marijuana plant is not asexual. There is both a female marijuana plant and a male one. The male plant creates a pollen which pollenates the female flower. After pollenation has occurred, the female flower produces seeds. If there is no male plant nearby, the female marijuana plant will continue to develop its flowers without seeds. This is called sensemilla. Usually male plants are used only for breeding purposes. Growers will tend to rip out of remove the male marijuana plants to avoid the females getting the seeds as this reduces its levels of THC. The female plant is what all growers want at the end of the day and they will often clone or buy feminized marijuana seeds to make absolutely sure that pollenation does not occur.
Below are several examples of the male marijuana plant in flower. So that you can tell the difference between the female and male plant, also check out our female marijuana plant gallery.