The flowering stage is the reproductive phase where the female cannabis plant transitions from vegetative growth to producing flowers, commonly known as buds. This period is initiated by a change in the light cycle, signaling that the season is changing and it is time to reproduce. Focusing energy on flower development, this stage ultimately determines the final yield, potency, and quality of the harvest. Successful cultivation requires attention to the plant’s unique needs, as the buds contain the highest concentrations of desirable compounds like cannabinoids and terpenes.
Typical Flowering Duration
The duration of the flowering stage for photoperiod cannabis varieties typically falls within a range of 8 to 12 weeks after the light cycle is switched to 12 hours of light and 12 hours of uninterrupted darkness. The specific genetics of the plant are the primary factor influencing how long this period lasts. Most modern hybrid strains are often ready for harvest around the 9-week mark.
Indica-dominant varieties generally have a shorter flowering time, often finishing in 8 to 9 weeks, as their genetics adapted to regions with shorter summer seasons. Conversely, pure Sativa strains, which originated in equatorial regions, can take significantly longer, sometimes requiring 10 to 14 weeks to fully mature. Autoflowering varieties are unique because their flowering is not dependent on the light cycle; they automatically begin the process after three to four weeks of growth, completing their entire life cycle in 10 to 14 weeks from seed to harvest.
Key Phases of the Flowering Stage
The flowering stage unfolds across several predictable phases, each marked by distinct physical changes. The initial period, often called “The Stretch” or pre-flower, covers the first three weeks after the light cycle change. During this time, the plant undergoes a rapid vertical growth spurt, sometimes doubling or tripling in height as it prepares to form flowers. This phase is characterized by the appearance of the first wispy, white hairs, known as pistils, which signal the start of bud site development.
Following the initial stretch, the mid-flower phase (weeks four through six) is when the plant begins serious bud development. Vertical growth dramatically slows down, and energy is redirected toward thickening the calyxes, the small structures that make up the flower. During this period, the buds increase significantly in mass and density, and the first signs of resin production, or trichomes, become visible.
The final stage, late-flower or ripening, begins around week seven and continues until harvest. Growth has stopped, and the plant focuses entirely on the final maturation of the flowers. The buds swell to their final size, and the production of cannabinoids and aromatic terpenes peaks. Visual indicators of maturity, such as the color of the pistils and trichomes, start to become evident in this phase.
Factors That Alter Flowering Time
While genetic makeup sets the inherent timeline, various external factors can cause the actual flowering duration to deviate from the expected range. Genetics are the most significant variable, determining the plant’s natural propensity for a short, medium, or long flowering cycle.
Environmental stress can significantly stall or delay the maturation process, extending the overall flowering period. Light leaks during the necessary 12 hours of darkness for photoperiod plants are a common issue that can confuse the plant, sometimes causing it to revert to the vegetative stage or delay flower development. Temperature extremes also play a role; low temperatures can slow the plant’s metabolism and prolong the flowering phase.
Improper nutrition can act as a stressor that alters the timeline. A deficiency in certain nutrients, or an excess of nitrogen late in the cycle, can disrupt the plant’s hormonal balance and slow flower development. Maintaining a strict 12/12 light cycle is non-negotiable for photoperiod strains, as inconsistency in the dark period inhibits the hormonal shift required for consistent flowering.
Determining the End of Flowering
The end of the flowering stage is determined not by the calendar, but by the physical maturity of the buds, observed through specific visual indicators. One primary sign is the change in the pistils, the white, hair-like structures on the flowers. Initially white, these hairs gradually darken, curling inward and turning to shades of red, orange, or brown as the flower ripens. When 70 to 90 percent of the pistils have changed color, the plant is nearing its peak maturity.
The most accurate method for confirming harvest readiness involves inspecting the trichomes, the tiny, resin-producing glands on the buds, typically requiring a magnifying tool. Trichomes progress through three distinct color phases: clear, cloudy (milky), and amber. Clear trichomes indicate the flower is immature, while cloudy or milky trichomes signify the peak potency of psychoactive compounds. A higher percentage of amber trichomes indicates that the compounds have begun to degrade, leading to a more sedative effect. Growers determine the optimal end of flowering by harvesting when the trichomes show a desired ratio of cloudy to amber, aligning with the intended effect.