Female marijuana plants produce seeds only when fertilized. Under normal circumstances, a female plant’s natural purpose is to develop unfertilized flower clusters, commonly known as buds. Seed production is triggered by two biological mechanisms: receiving genetic material from a separate plant or, in a survival response, generating its own pollen for self-fertilization. The presence of seeds significantly alters the plant’s chemistry and the resulting quality of the harvested material.
The Goal of Cultivation: Sinsemilla
The modern cultivation of cannabis prioritizes seedless flowers because they yield a superior product for consumption. The term used to describe this preferred seedless flower is sinsemilla, a word derived from Spanish meaning “without seed.”
When a female plant is prevented from being fertilized, it directs metabolic energy toward the production of resin, which contains high concentrations of cannabinoids like THC and CBD, and aromatic terpenes. This redirection results in a more potent, flavorful, and higher-quality final product. Conversely, if the female flower is pollinated, the plant’s energy is diverted away from resin production and channeled toward seed development.
Seeded flowers contain lower concentrations of active compounds because the plant focuses on reproduction. Producing seedless cannabis is achieved by deliberately separating female plants from any potential sources of male pollen. This controlled environment thwarts the plant’s genetic imperative to reproduce, maximizing the accumulation of desirable compounds in the flower.
Seed Development Via External Pollination
The most common way female plants produce seeds is through external fertilization from a separate male plant. Cannabis is naturally a dioecious species, meaning it produces distinct male and female plants, each bearing only one type of reproductive organ. The male plant develops small pollen sacs that burst open and release pollen into the surrounding air.
Pollen transfer is primarily facilitated by wind, which can carry the microscopic particles over significant distances to reach a female plant. Once a pollen grain lands on the sticky pistil (the hair-like structures) of a female flower, it germinates and forms a pollen tube. This tube travels down to the ovule, where the male gamete fuses with the egg cell, initiating fertilization.
Following fertilization, the ovule begins to mature, developing a hard outer shell and an embryo within a protective structure, which becomes the seed. Seed maturation typically takes four to six weeks from the point of pollination. While controlled breeding operations intentionally introduce male pollen to create specific genetic crosses, accidental pollination is prevented by removing male plants from the growing area before their sacs open.
Self-Seeding: The Role of Hermaphroditism
Female plants can also produce seeds without a separate male through hermaphroditism. This occurs when a genetically female plant develops male reproductive organs, making it capable of self-pollination. This is often a survival mechanism triggered by environmental stress, ensuring the plant can create seeds and continue its lineage. These male organs appear as small, pale yellow, banana-shaped anthers that emerge directly from the female flowers.
These structures produce and release viable pollen, which then fertilizes the female flowers on the same plant. The resulting seeds are often called “feminized seeds” because they carry the genetics of a female plant and are highly likely to grow into new female plants.
The development of male flowers is induced by various stressors, including interruptions to the light cycle during the dark period, which signal the plant that its season is ending. Other triggers include extreme temperature fluctuations, severe nutrient deficiencies, or prolonged periods of late harvesting. This biological plasticity allows the plant to switch reproductive strategies when it perceives a threat to its survival.