Cannabis plants are sensitive to light cycles – especially during the flowering phase. But many growers underestimate one problem: light pollution. Artificial light sources such as streetlights or garden lighting can disrupt the natural dark cycle, leading to stress, reduced yield or even hermaphroditism. In this guide, we explain how to recognize and avoid light pollution and protect your plants in the best possible way.
Why light pollution is a problem
1. disturbance of the dark cycle
Cannabis is a short-day plant: in the flowering phase, it needs at least 12 hours of uninterrupted darkness. Artificial light interrupts this rhythm and signals the plant to remain in the vegetative stage – flowering is delayed or does not occur.
🔍 Counter-perspective: Some autoflower varieties are less sensitive to light. But even they can react in a stressed manner if they are permanently disturbed.
2. risk of hermaphrodites
Stress caused by light pollution can lead to female plants producing male flowers(hermaphroditism). The result: self-pollination and seedy buds.
⚠️ Assumption tested: Not every light disorder leads to hermaphrodites – but the risk increases significantly.
Avoiding light pollution: 5 practical tips
1. site analysis before cultivation
- Check light sources at night (lanterns, building spotlights).
- Use the shade of trees or fences as a natural barrier.
2. light-proof covers
- Black tarpaulins or dense nets block stray light.
- Mobile pots allow plants to be placed in the dark if required.
3. automated lighting control
- Timers guarantee precise light cycles indoors.
- Green light (500-520 nm) disturbs the dark phase less – ideal for night-time checks.
4. minimize reflective surfaces
- White walls or foils can reflect scattered light. Matt black is better.
5. choose genetics
- Robust varieties such as “Northern Lights” or “Frisian Duck” tolerate slight disturbances better.
Alternatives for urban growers
- Guerrilla growing: Use remote areas with natural shade.
- Indoor cultivation: complete control over light conditions.
💡 Alternative perspective: LED full spectrum lamps with a UV component can increase resistance in indoor areas.
Conclusion
Light pollution is an avoidable risk – with planning and the right techniques you can protect your crop. Prioritize darkness in the flowering phase and choose resistant genetics to avoid disappointment.