The flowering phase marks the reproductive stage for the cannabis plant, during which it shifts its energy away from vegetative growth to focus entirely on producing flowers, commonly called buds. This transformation is signaled by a change in the light cycle for photoperiod strains, which mimic the shortening days of late summer and autumn. The duration of this flower production period is highly variable and depends on the plant’s unique genetic makeup. This period culminates when the plant reaches peak maturity, signaling the window for harvest.
Typical Flowering Durations by Strain Type
The length of the flowering period is strongly dictated by the plant’s lineage, or whether it is predominantly Cannabis indica, Cannabis sativa, or a hybrid of the two. Indica-dominant strains are known for their relatively short flowering times, often completing their cycle in approximately seven to nine weeks from the start of flower initiation. This quicker maturation is a trait developed over time in their native, often harsher, climates.
Sativa-dominant varieties, which historically grew in warmer, tropical regions, require an extended flowering period. These strains typically need 10 to 14 weeks or even longer to reach full maturity. The increased time allows the plant to develop larger, more airy flower structures.
Hybrid strains fall somewhere between these two extremes, with their final flowering time depending on which parent genetics are dominant. Many common hybrids will finish within an intermediate duration of eight to ten weeks. Autoflowering plants operate differently, as their bloom cycle is triggered by age rather than light reduction due to the incorporation of Cannabis ruderalis genetics. They complete their entire life cycle in a fixed timeframe, often taking six to eight weeks for flower development within a 10-week total from seed.
The Stages of Flower Development
Regardless of a strain’s ultimate duration, the flowering phase consistently progresses through three distinct developmental stages marked by visual changes. The first stage, known as the transition or “stretch” phase, lasts for approximately the first three weeks of bloom. During this time, the plant undergoes a rapid vertical growth spurt as it prepares for reproduction, sometimes doubling or tripling in height.
Towards the end of this initial period, the first signs of flower production appear as small clusters of pre-flowers, from which thin, white hair-like structures, called pistils, emerge. The plant then enters the mid-flower or bulk phase, usually spanning weeks four through six, where vertical growth largely ceases. Energy is now focused on mass accumulation, and the tiny flower sites rapidly develop into recognizable buds with numerous white pistils.
The final phase is late flower or ripening, which begins around week seven and continues until harvest. During this time, the buds increase in density, becoming firm and heavy. The plant’s resin production intensifies, leading to a noticeable increase in the concentration of microscopic, mushroom-shaped glands known as trichomes. This stage signifies the final push toward maturation.
Indicators of Harvest Readiness
The most precise determination of harvest readiness relies on observing two physical indicators: the pistils and the trichomes. Pistils, the hair-like structures on the buds, transition in appearance as the flower matures, shifting from bright white to darker shades of red, orange, or brown. Most growers aim to harvest when 70% to 90% of these pistils have darkened and begun to curl inward, suggesting the flower is fully formed.
The most accurate method for assessing peak potency requires magnification, such as a jeweler’s loupe or a microscope, to examine the trichomes. These resin glands contain the cannabinoids and terpenes that determine the plant’s effects. The color of the trichome head indicates its maturity level, following a sequence of three visible stages.
Trichome Maturity Stages
Initially, trichomes are clear, indicating that the cannabinoids are immature. They then turn cloudy or milky white, which signals the period of peak cannabinoid concentration, offering a more stimulating effect. The final stage is amber, where THC begins to degrade into compounds like Cannabinol (CBN), which is associated with more relaxing and sedative effects.
The optimal harvest window is a matter of preference. It generally occurs when the trichomes are a mix, with the majority being milky white and a smaller percentage (often 10% to 30%) having turned amber.