forgot to turn light off flowering

I Forgot To Turn Light Off Flowering: Now What To Do!

Lighting, as easy as it may sound for cannabis growth, can cause serious predicaments at times. Forgetting to turn off the lights is such an occasion. 

So, what happens if you forgot to turn off light flowering?

If you forget to turn off the light, you’ll see a small number of seeds in the buds because of reveg. This happens because plants couldn’t receive enough darkness to promote the creation of Florigen. It is a flowering hormone essential for growth. And that ultimately brings the blossoming process back to its vegetative state. 

Want to know more? Stick with me while I discuss the consequences. 

Now, let’s begin.


  • If the extra light time is around 6 hours, then leave them for 6 hours of night time.
  • For 12 hours and more light time, leave the lights on for the next dark cycle.
  • Don’t be scared if you see some buds going back to the vegetative stage.

How Long Should the Lights be Left on During the Flowering Stage?

You should leave the lights on for 12 hours during the flowering stage. The 12/12 cycle is the most typical flowering stage. 

The amount of light your cannabis plants receive throughout the flowering period directly affects their size. It also affects the density and quantity of their final buds.

Grow light flowering room

This means that the resin production and bud density will increase with more nutrients. The 12/12 cycle is the most typical flowering stage. 

Lighting during the blooming stage of marijuana is crucial. The plant enters its flowering phase after receiving at least 12 hours of darkness. 

However, it still requires high levels of light to form buds. We can only provide them with a total of 12-hr of light after 12-hr of darkness.

Since cannabis plants require as much light as possible during the flowering stage, any schedule that provides less than 12 hours of illumination each day will be bad. 

It will result in less quality and quantity of the final product.

Should You Turn Off the Light During Flowering?

No, you should always use a balanced light and dark cycle during the flowering stage. Otherwise, your plants will get negatively affected.

To initiate the blossoming response, you just need to supply sufficient darkness. At night, when the effect of darkness is greatest, each plant will grow to its fullest potential.

A 24-hour period without any light will have no negative effect on the plants. Since photosynthesis requires light, they couldn’t do it at night anyway.

Cannabis under continuous light
Source: mygardenplant

The availability of nutrients, lighting conditions, relative humidity, and temperature, among other factors, will all have an impact. 

This changes the optimal time to act. Each plant and each day will have its own unique variation. It’s inconceivable that a plant would actively seek out total darkness.

After the plant has finished flowering, you can let it rest in the dark for a few days. Perform this for a period of at least 24 hours of continuous darkness. 

This could be the moment when the plant keeps on generating oil. The lack of light would prevent significant degradation of those oils.

It is recommended to turn off light for extended periods of time during the flowering stage. 

So, What Will Happen If I Forget to Turn Off the Lights?

Plant growth can be stimulated by turning off the lights for a short period of time. As a consequence of this, individuals could regress to a state that is more vegetative.

That would require at least a day that is 23 hours long for it to take place. It’s possible that additional seeds can be found in the buds.

Here’s how the plants look like after a period of continuous light shedding on them according to a grower-

From our point of view, there is now no basis for a protracted period of nighttime. During the night, the plant will create either hormones or enzymes.

A flash of light will surely destroy it. Even though there are more daylight hours, the plant’s flowering hormone never reaches a sufficient level. 

If the hormone level drops severely, then your calyxes might not swell too.

A whole night of darkness should revive it. Even after 12 hours of daylight (after the night), it won’t be gone.

As for how long a plant needs to flower, that is also strain- and situation-specific. 

Genetically, true hermies will always produce male flowers first. Male flowers develop because the flowering process is prolonged due to light leaks.

If you still can’t be sure about the light cycle during the flowering stages, here’s a visual presentation-

I hope you can understand the concepts more easily now.

Possible Outcomes and Their Solutions

Turning off lights might end up in a situation. Some of them are good for cultivation. Others may not be pleasant. 

So, what will happen If I accidentally left grow lights on overnight?

Leaving lights on for a single night won’t harm the plants. It will bear minimum effect. However, if you keep them on for a prolonged time, it will have dire consequences. It may hinder plant growth, prevent flowering, or even burn damage to the flowers.

Whichever the outcome, I have noted them all. That’s not all. I have got the best possible solution just for you.


The plants may revert to a more vegetative state. You know that it takes more than one 23-hour day of light to accomplish that.

Cannabis leaves after a night in the dark
Source: Reddit

Buds can be a good source of extra goodies, such as seeds. If you can sell them, it might be nice to have a few extra packs of inexpensive seeds.


If you want to stop revegetation, you will need to adopt a lighting schedule. Try using a 12-12 light schedule. You can use a timer for this one.

Hormone Growth Halt:

During periods of darkness, the plant may produce hormones or enzymes. It can be destroyed by light. Because there are more daylight hours, the hormone never reaches its peak rate. 

This is the amount that would signal to the plant that it is time to begin flowering. Therefore, you no longer require that hormone.


To maintain the right hormone level, 12 hours of darkness is more than sufficient. After the darkness, there will be 12 hours of light. That will be long enough to get rid of the issue.

Overheating the Plants:

If the leaves nearest the light source begin to brown, you will know the plant is overheated. 

If you see the earliest symptoms, you may be able to prevent further harm. This appears as faint outlines on the outer surfaces of the leaves. 

Leaf curling may also occur if the plant is placed too close to the light source. Your clones may also become yellow without any roots.


Using a light timer is the best way to deal with such a problem. The presence of adequate ventilation is also usually helpful in alleviating this problem.

The thing about grow lights is that they won’t turn off by themselves, would they? So, if you want to avoid the same thing again, here are some reliable timers you can get-

However, it’s very common for the timer to fail at times. So, what happens if your timer failed during flowering?

If your timer fails during flowering, then your buds can revert to a vegetative state. However, 12 hours of uninterrupted light won’t hurt much. Especially if you’re using trellises for an even canopy. 

Still, be sure to take care of the timer every week.

Wrong Light Schedule:

Regardless of the circumstance, you shouldn’t keep the lights on all the time. If you neglect to turn them on, the problem could get even more severe.

It is easy to mistakenly stunt the growth of a plant. This can happen by making even a minor alteration to the plant’s light cycle. At first, you might think that this is ridiculous.

To properly cultivate cannabis, the plant must be exposed to light for between 18 and 24 hours. This is during the vegetative stage and for only 12 hours during the flowering stage.


Try to check the timer settings before you go to bed!


This is comparable to a human adolescent. This is when the plant will grow tallest. The vegetative stage can last anywhere from 3 to 16 weeks. It calls for 18 hours of full-spectrum light and 6 hours of darkness.

Frequently Asked Questions (FAQs):

What Happens If I Don’t Turn Off the Grow Lights?

Your plants are unlikely to suffer any long-term effects from just one night under growth lights. Nevertheless, leaving them on for long periods may stunt growth. It can prevent your plants from flowering, causing them to wilt and burn, and even kill them.

Can I Leave a Grow Light On All The Time?

The lights used in a plant shouldn’t be left on all the time. Plants can’t flourish without alternating periods of light and shadow. It has been hypothesized that they “relax” throughout the night. When plants stop actively growing, they take the opportunity to redirect growth resources to their tips.

Do Plants Need Less Than 12 Hours Of Grow Light?

In general, most plant species only need between 12 and 18 hours of sunlight per day. This is required to flourish, bloom, and produce fruit. It is possible to forgo using a grow light altogether if your plants have access to natural light. A window will suffice for this.


That will be all on forgot to turn light off flowering. Hopefully, you know the outcomes and their solutions now.

Do make sure you use a timer to avoid such circumstances. And do set up the lights properly. It’s important for the vegetation.

See you soon.

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