Female flowers begin to show as bracts at the various bud sites that occur at branch nodes and tips. Two white hairs (stigmas) will emerge from the end of the pear-shaped bracts, looking very much like their precursor female preflowers. The bracts gradually swell, becoming covered in a "resin" made up of glandular trichomes-the tiny THC-containing crystals that glisten like diamonds in the light. As the female flowers mature, thousands of these swelling bracts form into the clusters known as buds, eventually filling branches to form long colas. Kept free of male pollen and fed with the finest in phosphorous-rich nutrients, females will swell in size, producing trichome-laden buds just begging to be consumed.
When a plant shows both male and female flowers, it's considered a hermaphrodite and should be immediately removed from the garden. Whether you use these for cooking, making bubble hash or tossing into a compost pile, get rid of them as soon as you discover them. There are some unstable sativas that will show male flowers late into flowering. The yellow male "bananas" that pop out from almost fully formed buds can be removed as they're found and will do little damage at this stage.
A week or two into flowering, when males truly begin to show, they'll look like a miniature bunch of bananas hanging down as they slowly beginning to swell with pollen. You have less than a week to remove the males from your garden at this point, before they release their pollen and seed your entire crop. If you're interested in experimenting with seed breeding on your own, keep the males alive in a separate area well away from the females. They don't need to thrive-just keep them alive with fluorescents or low-watt grow lights. Place paper under the plants when the male flowers look close to popping open. Once you've collected the pollen, place it in a dry, sealed container. Lightly sprinkle or brush the male pollen onto developing female flowers to create seeds for future crops.