Light Leaks in Flower: Why They Ruin Harvests
By The Budometry TeamPublished Updated
During flower, the dark period must actually be dark. Interrupted darkness is one of the leading causes of hermaphrodite plants and stalled, airy buds.
Part of our pillar guide: Cannabis Grow Lights: Sizing, Height and Schedules
Where leaks come from
Tent zipper seams, unsealed cable ports, the passive intake flap, LED driver status lights, timers and power strips with indicator LEDs, and the door of the room the tent sits in.
The five-minute test
Wait for lights out, turn off every light in the room, sit inside or next to the tent for five full minutes so your eyes adjust, then look for glow. Anything you can see, the plant can see.
Fixes
Gaffer tape over seams and ports, electrical tape over indicator LEDs, a light-proof duct sleeve on passive intakes, and moving power strips outside the tent.
Frequently asked questions
- Can I use a green headlamp during lights-out?
- Brief green light is widely used and generally low-risk, but the safest habit is doing all your work during the light period.
The full guide on this topic
Cannabis Grow Lights: Sizing, Height and Schedules
How to size an LED to your tent, set hanging height by stage, run 18/6 and 12/12 on a timer, and hit the PPFD and DLI numbers that actually grow flower.