The transition from vegetative growth to the flowering stage in many plants is marked by a sudden and intense period of vertical growth, commonly known as the “flowering stretch.” This phenomenon occurs immediately after the plant receives the environmental signal to begin reproduction, such as a switch to a shorter daylight cycle indoors. The stretch is a final, rapid surge in stem elongation before the plant dedicates its resources entirely to flower production. This initial growth phase can dramatically alter the plant’s final structure and height.
The Biological Drive Behind Rapid Growth
The primary mechanism driving this rapid vertical expansion is a shift in the plant’s internal hormonal balance. When the flowering cycle is triggered, the plant alters the production and concentration of two main phytohormones: auxin and gibberellin (GA). Auxin is generally responsible for cell division and elongation, while gibberellin specifically promotes stem elongation by stimulating cell expansion within the internodes.
The onset of flowering often sees a surge in gibberellins, which acts as a growth stimulant for the stem. This hormonal signal directs the plant to quickly increase its height, a natural survival instinct to compete for light resources before focusing energy on reproduction. This rapid growth is an evolutionary adaptation, helping the plant canopy rise above competitors in a natural setting.
Identifying the End of the Stretch Phase
The most direct answer to when the stretch stops is typically between two to four weeks after the initiation of the flowering cycle. This timeframe can vary, but the end of the second week or sometime within the third week marks the deceleration for many common varieties. The plant has completed its most intense vertical growth and begins to transition to flower mass development.
Growers can identify the end of the stretch by observing a dramatic tightening of the internode spacing. During the stretch, the distance between new branch sets is significantly elongated, but once the phase concludes, new growth appears much more compact.
The visual shift is characterized by the plant’s overall shape changing from rapidly climbing to becoming more bushy or laterally dense. While some minor vertical growth may continue, the explosive, daily height increase ceases, signaling that the plant’s energy is now being channeled into developing reproductive structures.
Factors Influencing Stretch Duration and Intensity
The exact duration and magnitude of the vertical stretch are determined by the plant’s genetics. Varieties with a Sativa dominance tend to exhibit a longer, more intense stretch, sometimes doubling or tripling their height during this phase. Conversely, Indica-dominant varieties stretch less dramatically and for a shorter period, often only increasing their height by 50% to 100%.
Environmental factors also play a substantial role in modulating the stretch response. The light spectrum delivered to the plant can influence stem elongation, as a higher proportion of red and far-red light can encourage vertical growth. Light intensity is also a factor; plants receiving insufficient light will stretch excessively as they instinctively reach upward to find a stronger source, a phenomenon known as etiolation.
Temperature is another variable, with warmer temperatures promoting more extensive stretching. Maintaining a significant difference between day and night temperatures can help regulate this growth, as warmer nighttime temperatures can sometimes suppress the activity of gibberellin, the hormone responsible for elongation.
Growth Characteristics After Stretching Ceases
Once the vertical growth phase is complete, the plant reallocates its energy away from stem elongation and toward the reproductive structures. The focus shifts entirely to flower maturation and mass accumulation, often referred to as “bud fattening.” The plant’s architecture remains largely fixed in terms of height, and the primary change is in density and volume.
The internodes that were widely spaced during the stretch begin to fill in as the newly forming calyxes and bracts multiply. This results in the formation of solid, continuous flower structures rather than separated clusters.
This period is also when the plant initiates the visible production of resin, which appears as tiny, sparkling trichomes on the surface of the developing flowers and leaves. The plant’s energy is now used to synthesize cannabinoids and terpenes, which are housed within the resin glands. The lateral branches will continue to swell and gain mass, but the upward growth of the main stem is effectively halted.