There are a few ways to pollinate cannabis plants.
First, Understand How to Differentiate Sexes
If you are only interested in cultivating seeds and plan to grow the sexes in the same room through to the pollination process, once you know the sexes of the plants you would want to stagger combining them until the timing works out so that the female plants are set to flower about one week before the males. Be sure to cull out any male and female cannabis plants that require a disproportionate amount of effort to cultivate so that you reduce the risk of weak genetics being passed on.
Male plants take about two weeks less to flower than female plants, which may take up to eight weeks. Males will have a little ball where stem meets stalk and will develop little bags that will eventually contain the pollen, whereas the female plant will produce two small hairs. Female cannabis plants tend to be smaller with regular branches that have more leaves and internodes than the male plants.
Until you get the hang of cultivation, it is best to use male and female marijuana plants of the same strain. Most folks prefer to separate the females once the sex shows to ensure that pollination is only by males with genetic characteristics of their choosing. Generally speaking, sativas tend to take longer than indicas to mature.
Producing Strong, Plentiful Plants
Once your male cannabis plants begin to show their qualities, you may choose to harvest pollen from all of them, or just the best of the best. It’s recommended that when it looks like the males' flowers are about to open that you stop running the fans in your grow room, but keep the air circulating so that humidity doesn't become a problem.
Those wishing to pass on specific genetic characteristics are advised to watch the plants and observe which ones can resist pests and mold, have a potent smell and short distances between nodes and maturation times. Seeds fertilized with this pollen will typically end up with a ratio of about half of the resulting plants being male and half female, though some crops will yield quite a bit more of one of the genders.
Female plants come to produce male pollen sacks in one of three ways. If exposed to unfavorable conditions such as poor nutrition, bad lighting, and other factors that stress the growing process, female plants may become hermaphroditic to ensure that their genes go onto another generation. These plants produce the structures of both sexes so that they may fertilize themselves, but they may also pollinate other marijuana plants.
Hermaphrodites create the least pollen on average. Though many of the seeds pollinated from these plants will yield female plants – favored because they don't have seeds and have a higher THC content than male plants – some of the seeds from this process could produce plants that are hermaphroditic in nature, which tend to make for seedy, generally-undesirable plants. Seeds that inherit hermaphroditic genes are a second way that female cannabis plants may develop male characteristics.
The third, less risky, and preferred method is to use chemicals, such as gibberellic acid and colloidal silver, to induce the female plants to produce sacks that will yield pollen with female genes. This pollen may then be used to pollinate cannabis by fertilizing female plants to produce all female seeds.
Methods for Harvesting Pollen
There are several methods commonly used for the harvesting and application of pollen. Some people prefer to cut each of the pollen sacks off one by one. Another technique used is to put a bag over the flowering stems for collection. If you do not plan on storing the harvested pollen, it is best to use it within three to four days, as past that point viability for reproduction is severely reduced.
If you intend to store it, be sure to take all measures to avoid moisture contamination throughout the process, from drying to thawing, as that will kill the pollen. Allow the pollen to dry for one week. You may store pollen for up to a year in the freezer. Don't forget to label each container with the strain name and date of freezing. Those people concerned with passing on specific genetic traits also like to indicate smell, hardiness, and description of plant structure on their labels, along with any other characteristics that are important to them.
Pollinate Cannabis to Grow Seeds
Some folks don't want to bother with harvesting pollen and like to keep it simple and just put the male(s) and females in the same room and run fans to mimic wind, which in the outdoors plays the leading role in pollinate cannabis naturally. After pollen collection, most people will use a brush, cotton ball, or their fingers to apply it to the female hairs, known as stigmas. These methods mimic pollination caused by insects, animals, and people out in the wild.
Things to be wary of to avoid include inadvertent pollination is to change clothing between grow rooms, keep pets away from the grow and your clothing, and ensure that you have a good HVAC system, and high-quality filters. After pollination, germination takes 10-20 minutes, and fertilization occurs within one to two days once the male, or female, genetics in the pollen makes its way down the pollen tube to the ovule, within which the seed will develop.
Seeds could take six weeks to mature, even a little bit longer. The seeds will pop out easier once the calyxes begin to open. Seeds that are green to light tan in color need more time, so leave them be. They are ready once they become dark brown or display distinct tiger stripes. You may have to make an effort to keep the plant alive until they are ready. Once you've harvested your seeds, let them dry for one to two weeks. Freeze them in a light blocking canister, that will protect the seeds from moisture. The female plants used for seed production will still be OK to smoke, just less potent. Seeds treated with chemicals to induce pollen are poisonous, so discard them.
If growing is new to you, or if you're not at a point where it's feasible to pollinate cannabis on your own, there are various businesses that offer seeds and clones.