When propagating new genetics, the precise timing of the harvest is the single most important factor for maximizing seed viability. Harvesting cannabis seeds is distinct from harvesting flower buds, as the goal is to collect a mature embryo rather than a resin-rich final product. A mature seed contains the necessary protective structures and nutrient reserves to ensure successful future germination and plant growth. Rushing the harvest results in weak, non-viable seeds, while waiting too long risks losing them to natural dispersal.
Timing Seed Development: Weeks After Pollination
Seed maturation begins immediately after a female flower is successfully pollinated by male cannabis pollen. The initial stages of development involve the fertilized ovule transforming into a seed within the calyx. This phase requires the plant to redirect a significant portion of its energy away from flower production and toward embryo development.
The time required for a seed to fully mature after pollination is an estimate that varies depending on the specific strain and environmental conditions. Generally, cannabis seeds require a minimum of four to six weeks post-pollination to complete their development cycle within the calyx. Some strains may take slightly longer, extending the window to seven or eight weeks in certain environments.
This timeframe serves as a preliminary guideline but should not be the sole determinant for harvesting. Environmental factors like temperature and nutrient availability influence maturation speed; for instance, cooler temperatures can slow metabolic processes, extending the required period. Physical inspection remains the most reliable method for determining peak readiness.
Visual and Physical Indicators of Seed Maturity
The optimal harvest time is determined by observing the physical characteristics of the seeds. A mature seed is designed to survive harsh conditions, and its appearance reflects this protection. The first indicator of maturity is the seed’s color and patterning.
Immature seeds will appear pale, often white or light green, and possess a soft, pliable outer shell. As the seed matures, the outer coat, known as the testa, darkens significantly, transitioning to shades of dark brown, gray, or black. Many fully mature seeds also develop distinctive, mottled patterns or “tiger stripes” across the shell surface.
The seed shell’s texture is an important physical cue indicating viability. A seed that is ready for harvest will have a hard, tough outer shell that resists gentle pressure. If a seed is easily crushed or squishes when lightly squeezed, it is immature and unlikely to germinate successfully.
The final stage of natural maturation involves the seed preparing for dispersal. Mature seeds will often loosen within the calyx and can be easily dislodged or naturally fall out with a slight disturbance. If significant force is required to remove the seed, it may benefit from a few more days of maturation. Harvesting should focus on branches where the calyxes show signs of browning and drying out, signaling the completion of the seed cycle.
Immediate Steps After Harvesting to Ensure Viability
Harvesting the seeds at the correct maturity is only the first step; proper post-harvest handling is necessary to maintain long-term viability. Freshly harvested seeds contain residual moisture that must be eliminated before storage to prevent mold growth. The immediate step after separation from the plant matter is controlled drying.
Seeds should be spread out in a single layer on a clean, dry surface, such as cardboard or a mesh screen, in a well-ventilated area. The ideal drying environment is cool and dark, with temperatures maintained between 60°F and 70°F and relative humidity kept low, ideally around 40 to 50 percent. This slow, controlled drying prevents the seed embryo from being damaged by rapid moisture loss.
The drying process typically takes about one to two weeks, depending on the initial moisture content and ambient conditions. A simple test for sufficient dryness is the “snap test,” where a properly dried seed will resist crushing and may produce a slight snap sound if pressed firmly. Once dried, the seeds are ready for short-term storage preparation, which involves placing them in airtight containers.
Airtight glass jars are suitable for storage and should be clearly labeled with the strain name and harvest date. Storing the containers in a cool, dark, and dry location minimizes the degradation of the seed’s genetic material. This attention to moisture removal and environment control ensures the seeds retain maximum germination potential.