Light & Light Cycles
Light Cycle
A light cycle is the daily pattern of light and darkness a plant receives, which controls growth and flowering.
What a Light Cycle Controls in Cannabis Growth
A light cycle refers to the duration and timing of light and darkness a plant experiences within a 24-hour period. In cannabis cultivation, light cycles are one of the most powerful tools growers use to control plant behavior, including vegetative growth, flowering, and overall development.
The Science Behind Light Cycles and Photoperiodism
Scientifically, light cycles relate to photoperiodism (a plant’s response to the length of day and night). Cannabis is a short-day plant, meaning it begins flowering when nights become long enough to trigger reproductive hormones. This response is regulated by phytochromes (light-sensitive proteins that help plants detect changes in light and darkness).
How Photoperiod Discovery Shaped Modern Growing
The study of photoperiodism dates back to the early 20th century, when botanists discovered that it was the length of uninterrupted darkness—not light—that triggered flowering in many species. This discovery shaped modern greenhouse and indoor growing techniques.
Common Light Cycles Used in Cannabis Cultivation
In cannabis cultivation, common light cycles include 18/6 (18 hours of light and 6 hours of darkness) for vegetative growth and 12/12 for flowering photoperiod plants. Extending light hours keeps plants in vegetative growth, while reducing light triggers the flowering stage. Autoflowering cannabis, by contrast, flowers based on age rather than light cycle and can flower under long or constant light.
Why Consistency in Light Cycles Is Critical
Consistency is critical. Light interruptions during the dark period can confuse plants, causing stress, delayed flowering, or hermaphroditic traits. For this reason, light leaks and inconsistent timers are common grow-room problems.
How Light Cycles Affect Plant Size and Growth Speed
Light cycles also influence energy use, plant size, and development speed. Longer vegetative light cycles promote faster growth, while shorter cycles conserve energy and control plant height.
Why Light Cycle Management Matters for Growers
Light cycle management is closely related to growth stages, photoperiod plants, autoflowers, flowering triggers, and environmental control. For cannabis growers, mastering light cycles allows precise control over plant timing, structure, and yield.
Related terms:
Photoperiod, Vegetative Stage, Flowering Stage, Photoperiodism, Phytochrome, Autoflowering Cannabis, Light Schedule, Grow Room Timers.
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