My cannabis plant stopped flowering and is turning yellow/brown. This is my first grow and I was wondering if you could help me save it or if there’s any hope for it at all.

By Lee G Lyzit | Last updated: May 2, 2023

gelato OG suffering from yellowing leavesScreen capture from submitted video.
Although the video you included does show some droopy, yellow, and brown leaves, it appears to me that you have a more significant problem going on in the flowering room.

When cannabis plants produce single-leaf growth, as your plants are exhibiting, it is most commonly associated with an incorrect photoperiod or significant light leaks during the “lights off” period.

Light Cycles for the Flowering Period

For a cannabis plant to begin its flowering cycle, it must be exposed to an increased “dark” or “lights off” period. Aside from the autoflowering strains (cannabis ruderalis), which are rarely cultivated indoors, cannabis will not produce its reproductive organs (flowers or pollen sacs) until it has experienced a long enough period of darkness.

The most commonly used light cycle for flowering cannabis indoors is a photocycle of 12 hours lights on and 12 hours lights off. The 12 hours of darkness are enough to trigger a hormonal response within the cannabis plant, thus beginning the reproductive cycle.

During the “lights off” is also when much of the actual flower development occurs. An incorrect photoperiod or a reoccurring disruption during the dark cycle could cause a flowering plant to revert back to vegetative growth.

One of the most common traits of a cannabis plant reverting back to a vegetative stage is single-leaf growth. This is what I believe is happening to your plants as they appear to be converting back to a vegetative stage of growth.

Again, this could be caused by either a light cycle that does not provide at least 12 hours of darkness or a significant reoccurring light leak during the “lights off” period. The goal for the flowering room is to achieve complete darkness during the “lights off” period.

Looking for Light Leaks

To troubleshoot your flowering room’s “lights off” period, you should physically check the room’s darkness. This involves more than just flipping off the lights for a few seconds and thinking that the room appears dark enough. It’s a good idea to spend at least five minutes in the garden during the dark cycle to see how dark it truly is.

After waiting five minutes for your eyes to adjust, turn around very slowly to get a full 360-degree view of the flowering room. Take careful notice for any signs of light leaks. This includes lights on electric devices in the room, such as atmospheric controllers, power strips, or light timers. The tiny lights on these devices don’t seem like they would affect the growth of plants but any light in the “lights off” period should be considered bad light. Electrical tape over the small lights on power strips and controllers will cover up the light.

Other common areas for light leaks to occur are around and through ventilation ports. Look closely at intakes, exhaust, and air-cooled ducting systems to ensure no light is entering the garden.

It is also a good idea to take a close look at your light timers to make sure they are functioning properly. A failing or incorrectly set timer can cause significant issues with the photoperiod of an indoor flowering garden. Once you identify and correct the lighting issue, your cannabis plants should produce dense flowers throughout the flowering stage instead of single-leaf growth. I hope this answers your question and helps you get back on track.

Keep on Growing,
Lee G Lyzit

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Plant Growth Plant Science Plant Disease Plant Health

Written by Lee G Lyzit | Grower, Writer

Profile Picture of Lee G Lyzit

Lee G. Lyzit has been involved in the cannabis industry for nearly 20 years. His passion for natural healing motivates him to learn as much as he can about the miraculous cannabis plant. Lee’s knowledge of cannabis gardening stems from his own extensive cultivation experiences and his past work as a hydroponic shop owner and manager.

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