When should grow lights be turned off?
Written by
Kiana Okafor
Reviewed by
Prof. Charles Hartman, Ph.D.Recognizing when to give your plants a period of darkness for their health is as much about the quality of light provided. All plants need a period of darkness to grow properly. I completely ruined my first basil crop by leaving the plants under constant light. To protect your plants from my mistakes, keep track of the dark cycles for each species. The timing you provide each plant with photoperiod is crucial for regulating growth hormones and flowering triggers.
Vegetative Plants
- Provide 6+ hours of darkness daily
- Maintain consistent on/off cycles
- Avoid light leaks during dark phases
Flowering Species
- Ensure 12 continuous darkness hours
- Use blackout curtains in grow spaces
- Never interrupt night cycles
Timer Systems
- Program gradual sunrise/sunset simulations
- Use WiFi-enabled controllers for scheduling
- Install backup batteries for power outages
Plants have a daily need for rest and recovery. The darkness allows plants to recover from photosynthesis during the daytime. I noticed my lettuce became very bitter if it did not get enough recovery time. The light cycle provides darkness for six to ten hours a day. Given a consistent schedule, the plant will be able to adjust and not have stress while growing.
Blooming plants require a distinct uninterrupted dark period. Exposure to light during nighttime cycles interferes with blooming hormones. My peppers shed their flowers after receiving brief lightning overnight by accident. You can achieve perfect blooming with twelve hours of good, solid darkness.
Autoflowering plants do not follow the same rules. These plants flower under constant light. I grow autoflowering cannabis plants with continuous light. You can non-comply with your plant's schedule if you use these types of plants. This makes them an easy option for beginners.
Transition photoperiods gradually when changing stages. Reduce light one hour daily over a week. My tomatoes adapted smoothly this way. You prevent shock by maintaining the health of your plants.
Automated timers maintain precision. Digital controllers replicate natural dawn/dusk transitions. My system adjusts automatically for seasons. You ensure perfect timing without daily monitoring.
Darkness duration affects nutrient uptake. Plants absorb minerals during rest periods. My spinach developed deficiencies with short nights. You balance light and dark for optimal nutrition.
Read the full article: Ultimate Guide to LED Grow Lights for Plants
