It is crucial to provide sufficient light to plants inside a grow space. Grow lights can extend your growing season and enable your plants to thrive. You can make your growing process more efficient by using plant grow lights. Remember, they can also be harmful to plants if you are not maintaining a proper lighting schedule. In this article, we will discuss can you leave grow lights on 24 hours a day? What are the advantages and disadvantages of keeping grow lights on 24 hours a day?
Quick Answer is Yes and No
Yes, you can keep the grow lights on for 24 hours when the plants are in the vegetative growth stage. During the vegetative stage, plants don’t need darkness. When you give them more light, it will force them to move to the flowering stage quickly and get more harvests per year.
No, it is not recommended to keep your grow lights on 24 hours a day. Keeping the lights on will force plants to grow quickly. Ideally, you can keep grow lights on for 12 to 18 hours. Moreover, plants need rest; otherwise, they will become ill and result in lower yields.
Why Plants Need Both Light and Darkness?
Plants are like animals and humans, and they also need a break from direct light. In other words, you can say they need to sleep as well. When the weeds are constantly exposed to light, they may experience stress, especially during the vegetative stage. Once the plants get exposed to disease, they become susceptible to pests resulting in disease and death of plants.
During the daytime, plants absorb sunlight and convert it into a source of energy. At night, plants convert this unstable energy into carbohydrates and store it for later use. For plant growth, photosynthesis is mandatory, and it can’t happen without light.
Respiration
The process of respiration can occur at any time, and during that time plants can rest, eat, and store energy for the next day to tap during photosynthesis. When plants are exposed to light for 24 hours, they don’t allow the respiration process to occur. It can result in unhealthy plants. Moreover, repetitive and frequent light exposure can reduce the crop’s yield. More importantly, when you turn LED grow lights off, it will allow them to rest.
In Which Stage You Can Keep Grow Lights on for 24 Hours without hurting plants?
Vegetative Stage
Growing indoor plants mean that you can manipulate the environment according to your needs. When you are growing indoor plants, you can keep your plants in the vegetative stage for maximum time. You can keep your plants under light 24 hours each day without any harm during the vegetative stage.
Germination Stage
According to studies, some temperature fluctuations are good for plants during germination.
What is the Ideal Light Cycle?
Marijuana plants need a specific amount of light to grow properly and produce maximum yield. There are two different growth periods. One is the vegetative stage, and the second one is the flowering stage.
Vegetative Stage: 18/6
When plants are in the vegetative stage, you can keep grow lights on for 18 to 24 hours per day.
Flowering Stage: 12/12
Cannabis starts to grow when plants get at least 12 hours of darkness each night. When cannabis starts budding, they need long dark nights until they are harvested or return to the vegetative stage.
Period |
Light |
Darkness |
Vegetative Stage |
18 to 24 hours |
0 to 6 hours |
Flowering Stage |
12 hours |
12 hours |
Warm Tips:
Remember that if your plants are not responding to 12 to 18 hours light, you need stronger LED grow lights. You might have to adjust the height of the grow light as well.
What If I Accidentally Leave Grow Lights on For 24 Hours?
Most growers want to know the answer to this question. If you forget to turn off light for 24 to 48 hours, there is no need to panic. However, it’s not a good thing, but it will not harm your plants. Remember, it is crucial to set the lighting schedule again as soon as possible. If the blackout goes on for more than 48 hours, you are putting your plants at risk. It can make your plants sick and lower your final yield.
What are the Potential Problems of Exposing Your Plants to Light for 24 Hours?
Cannabis seedlings that are grown under 24 hours of light will take much more time to show pre-flowers than those grown under 18 hours of light. Surprisingly, seedlings grown under 16 hours of light have shown pre-flowers early than those grown under 18 hours of light. However, it is recommended to light for less than 16 hours during the seedling phase.
Most gardening experts have consensus that doesn’t leave the lights on constantly throughout the lifecycle of plants. When plants are not taking enough rest, they will not produce the desired yield.
When cannabis is exposed to constant light, it absorbs lots of light and remains engaged in photosynthesis. On the plus side, it will result in the maximum growth of foliage. At the same time, it has some disadvantages as well. When the weeds are constantly exposed to light, they may experience stress, especially during the vegetative stage. Once the plants get exposed to disease, they become susceptible to pests resulting in disease and death of plants.
Continuous and too much light in a growth phase can disturb the plants’ natural growth process and dormancy. If you are keeping lights on for 24 hours, prepare yourself for the worst scenario. 24 hours of light exposure can damage and destroy your plants.
Conclusion: Can you leave grow lights on 24 hours a day?
Can you leave grow lights on 24 hours a day? It depends on different growth stages. Yes, you can keep plants under grow lights for 24 hours when they are in the vegetative stage. When they move to the flowering stage, they need 12 hours of uninterrupted darkness. Growers keep plants under light for 24 hours for maximum yield. However, it is not a good practice. Plants are like humans and animals, and they also need some dark time for photosynthesis. If the plants don’t have proper growth, they are at risk of illness and disease.