Harvesting cannabis seeds differs from harvesting flowers because the goal is to preserve the plant’s genetic blueprint for future cultivation or breeding. Seed harvesting requires patience and focused inspection of the female plant’s reproductive structures after successful pollination. The viability of the seeds depends entirely on allowing them to reach full maturity before removal. Identifying the perfect moment for harvest involves watching for specific visual and physical changes in the seed pod, often called the bract.
Understanding Seed Development Timeline
Seed production begins only after a female flower has been successfully pollinated by male pollen. This process diverts the plant’s energy away from cannabinoid and resin production toward reproduction. Maturation typically takes four to eight weeks following pollination, varying based on the strain’s genetics and environment.
The plant must remain alive and healthy throughout this period, which is longer than the harvest window for unseeded flowers. During this time, the developing seed forms a hard outer shell and accumulates nutrients to sustain the embryonic plant. Rushing this process results in underdeveloped seeds that are soft, pale, and have a low probability of successful germination.
Key Visual Signs of Mature Seeds
The most definitive indicators of readiness are found by examining the seeds and the bracts that encase them. A fully mature seed shifts color from soft, pale green or white to a dark brown, grey, or black hue. This darkening signals that the protective outer shell, or testa, has fully hardened and is prepared for dormancy.
Mature seeds often display a patterned surface, referred to as “tiger stripes” or mottling, appearing as darker markings against the base color. The surrounding bract, which houses the seed, will also show signs of finishing its life cycle by swelling, drying out, and turning a yellowish or amber-brown color.
When gently pressed, a mature seed should feel firm and hard, resisting pressure without cracking or collapsing. Another reliable physical sign is the ease with which the seed separates from the bract. A ready seed will often loosen naturally or pop out with minimal effort when slight pressure is applied to the dried pod.
Harvesting and Collection Methods
The collection method depends on the scale of the operation and whether only specific branches were pollinated. For small-scale collection, individual, fully matured seeds can be carefully plucked by hand or with tweezers directly from the bracts. This targeted approach allows the grower to select only the darkest, hardest seeds while leaving underdeveloped ones to mature further.
For larger projects where entire plants were seeded, the common practice is to cut the entire seeded portion once 70 to 80 percent of the seeds appear mature. These seeded branches are hung to dry slightly in a dark, well-ventilated space, similar to a flower harvest. Once dried, the seeds can be gently extracted by breaking apart the buds over a clean surface or by using a screening process to separate the dense seeds from the lighter plant debris.
Post-Harvest Drying and Storage
Proper post-harvest treatment maximizes the long-term viability and germination success rate of collected seeds. Freshly harvested seeds contain residual moisture that must be removed to prevent mold growth and spoilage during storage. The seeds should be spread in a single layer on a clean, dry surface, such as a paper towel or cardboard, and allowed to air dry for several days up to two weeks.
The drying environment should be dark and well-ventilated, maintaining low humidity, ideally around 40 to 50 percent, and moderate room temperature. Once thoroughly dry, seeds should be stored in airtight containers, such as glass jars or specialized vials, to protect them from external humidity and oxygen. Ideal long-term storage involves a cool, dark environment, such as a refrigerator set around 40 degrees Fahrenheit, to maintain dormancy and preserve viability.