The embryonic plant protected by an outer shell, formed when pollen fertilizes the female plant. Cannabis seeds are ready to plant and grow once they successfully germinate, or once the root has broken through the seed. They can be found in multiple forms; regular, feminized, and auto-flowering. Home growers of cannabis often choose to grow feminized seeds to ensure that the adult plant will be a flowering female.
More About Seeds
As with all angiosperms, or flowering plants, cannabis produces seeds that contain all of the genetic information needed for growth and reproduction. When a seed is planted, the translation of this genetic material dictates each unique physical characteristic the mature plant will have. If these are desirable traits, like potency, smell, vigor, etc., a breeder can select for these through a long process of genetic stabilization through generations, which eventually leads to the creation of a cultivar, or strain.
Anatomy of a Seed
Cannabis seeds are about the size of a peppercorn, ovular in form, and pointed on each end with a ridge that transverses longitudinally on only one side from tip to tip. It is this ridge that opens up during germination. The other side opposite to the ridge is rounded. The body of the seed is brown, but underdeveloped and unfertilized seeds can have an off-white color and are typically smaller in size.
The body of cannabis seeds are spotted or striped, most commonly with light brown specks, but some varieties of cannabis can have red or yellow markings. Plant embryos are contained within seeds and house all of the cells that will eventually differentiate into leaves, roots, and stems. Embryos, found within the reproductive organs, are protected by an outer envelope called the pericarp. Crucial components of the plant embryo are the cotyledons, the first leaves to appear from the seed, and the radicle, which develops into the primary root. Once the seed germinates and begins its growth into a mature plant, special structures called root caps protect the growing tips of the plant.
Today’s common-market cannabis does not contain seeds; the cultivation practices that have made this widespread are rooted in fundamental biological concepts. Cannabis is a dioecious plant, meaning it has separate male and female organisms, just like humans. If a female plant matures in the presence of a male plant, pollen from the male will fertilize the female, and its bracts will contain seeds at the end of the flowering cycle. Seedless cannabis is commonplace even in the product originating from mass-produced outdoor cultivation, but not too long ago, this was not the case.
Around the middle of the 20th Century, growers discovered that culling male plants as soon as they display their sexed traits, would result in a crop containing exclusively unfertilized females, yielding cannabis flowers higher in THC that don’t require the removal of seeds before smoking. This seedless cannabis was from then on dubbed sinsemilla, which translates to “without seed” in Spanish. It is also commonly spelled sensimilla.
How Cannabis Seeds Are Produced
Cannabis seed production begins with the pollen grain of a male plant. From this grain, a pollen tube grows, producing male generative cells that disperse in the form of pollen. The migration of pollen into a female plant ovule triggers pistils to fall off and seed production to begin. The bracts, which contain the ovule, will then fill with seeds.
What Are Feminized Seeds and How are They Produced?
In 1982, Indian breeders made a major advance in cannabis botany with the development of the feminized seed. Popularized and marketed extensively by Dutch seed companies, feminized seeds produce female plants more than 99% of the time. Growers that use feminized seeds should still check to make sure no male plants have sprouted. Any variety of cannabis can be manipulated to make it feminized.
Cannabis seeds can be feminized by two different methods: chemical ethylene inhibition, and rodelization. In the first method, a chemical agent (colloidal silver, gibberellic acid, etc.) is applied to the plant to inhibit its production of ethylene, a plant hormone that induces female flower production. Rodelization is a less-used technique that involves exploiting a natural self-defense mechanism of the plant. An unpollinated female cannabis plant with fully mature flowers may, in some cases, grow pollen sacs to fertilize itself to ensure its propagation.
In both cases, pollen is collected and used to fertilize other female plants. Given the absence of Y chromosomes, seeds that result from the mature buds are female.
Where to Find Cannabis Seeds
Seeds are sold in brick-and-mortar locations legally in many countries across Europe, and are often traded online. As cannabis legalization expands in North America, more retail locations are carrying seeds as well. Feminized seeds are the most popular through market demand, but providers likely have access to mixed male and female seeds of any variety found feminized. Carefully sifting through cannabis before using the grinder will assure finding bagseeds before they are ground up. Professionally sourced seeds assure quality genetics and viability, but bagseeds are a great, cheap source of cannabis genetics for the hobbyist grower.
How to Store Cannabis Seeds
Seed providers sometimes vacuum-seal and freeze seeds for long-term storage, but commercially-available seeds in Dutch headshops are sold in small, plastic vials at room temperature and low humidity (6-12%).
Humidity and light is the main enemy for seed storage. Beyond that, seeds can remain viable for up to two years when stored in even the most haphazard conditions. Seeds swept up off the floor or found in the bottom of a drawer have been known to grow into vigorous young plants.
Germinating Cannabis Seeds
Germination is the process of beginning vegetative growth of the new cannabis plant. Sometimes referred to colloquially as “popping,” this process starts when the seed is exposed to water and light. The seed abandons its state of dormancy, or quiescence, and resumes essential metabolic processes that feed on energy stores to delicately rupture open the shell and grow its first root. This root will elongate until it has taken hold of the medium, after which it will pull two small embryonic leaves (cotyledons) from the seed shell. Cotyledons are in the seed prior to germination, and are not considered “true” leaves. The cotyledons will grow until they are about one centimeter long, and once the stem below this is around five centimeters tall, another set up true leaves will grow out of the top and the stem between the true leaves and cotyledons will continue to elongate.
Generally speaking, cannabis is a hardy plant that will grow, or even thrive, in a diversity of environments. However, to assure germination, several steps can be taken. One “quick and dirty” method calls for a moist paper towel inserted into a plastic bag. Once the first root appears, the seedling must be carefully transferred to some soil before the root takes hold to the paper towel. More professionally, seeds can be germinated in a peat pellet. Plant the seed only just below the surface. Once the seedling has taken hold in the pellet, directly transfer it to a pot; the roots will grow right through the soft fabric that encases the peat, at which point the pellet can be directly placed into soil. Whichever method is used, keep the temperature between 70 -90 degrees Fahrenheit (21-32 degrees Celsius), ideally at 78 degrees Fahrenheit (about 26 degrees Celsius), making sure to keep seedlings covered to maintain humidity. Seedlings and young cuttings require photosynthetically active radiation that is more heavily weighted in the blue portion spectrum; a common fluorescent desk lamp will suffice until they are about 5 inches, or about 13 centimeters, tall.
Cervantes, Jorge., The Cannabis Encyclopedia. Van Patten Publishing, 2015.