Since it didn't autoflower

I’m growing what I thought was white widow auto. Now, I vegged it for 8 weeks and it still hasn’t started to bud yet. I switched over to 12/12 a couple days ago. Now my question is, once it begins to flower because of the change in light schedule, can I switch back to say 16/8 without the worry of revegging?

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I’m a noob, on my first grow still. However, I’ve done tons of reading and research. I’d say it’s a bad idea. Reveg would be likely. Some of the more experienced guys and gals will chime in hopefully.

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Why did you think the seeds were auto? If you’re certain they are photo seeds, you need to stay at 12/12 til harvest. If you’re certain they are auto seeds, you can go to 18/6 once they are flowering.


I think @garrigan62 and @Hogmaster have worked with the autos quite a bit, and they’re both very knowledgeable. Hopefully they can help you out.

I haven’t worked with autos much more than to know they can be a little tricky sometimes.


I bought the 10 for 10 auto deal


Then they are auto seeds. They will eventually start to flower on their own. Go ahead and give them one full day of lights out if you don’t want to wait any longer. Then run a 12/12 schedule til all plants are blooming. You can then go back to 18/6 if you’d like.


If they were auto flower the light schedule wouldn’t mater -.

Here is some info. you should know on light schdules and flowering


Because of photoperiodism, you can easily induce flowering in cannabis plants simply by changing your grow room light cycles–reducing the light from 18 hours a day or more, to only 12 hours each day. Again, what is really important to the plants is changing from six hours of darkness or less to 12 hours of darkness. Within two weeks of switching the light cycles to 12 on and 12 off, you should see small buds starting to form.

I need to stress the point that your plants are very sensitive to any light during the dark period. If you have any light at all leaking into your grow room, during the 12 hours of dark– even momentarily–the PR can change back to PFR. This means that any light reaching your plants during the dark period may sabotage the flowering process… For this reason, you should never–not even for a moment–enter your grow room when the lights are turned off in the 12/12 cycle.

Before you make the switch to a 12/12 light cycle, you need to make sure your grow room has no light leaks. Enter the grow room while the lights are out and close the door behind you. Wait about 15 minute minutes for your eyes to adjust fully, then look around and make sure no light is entering the room. No light under the door, through a curtain, or shining from a CO2 generator or dehumidifier. I have made this last mistake myself. If any of your equipment produces light from the display, cover it with duct tape, making sure no photocells have been accidentally covered. If you can see your hand in front of your face, you have a light leak that needs to be fixed.

While simply changing to a 12/12 light cycle will induce flowering, there is a trick to jump start the process. Between the switch from an 18/6 to a 12/12 light cycle, let your plants sit in total, uninterrupted darkness for 36 hours. This will cause the PFR to drop substantially, giving the plants a strong signal to flower. After the 36 hours of darkness, begin the 12/12 light cycle. In a side by side experiment, I saw significant results from this method. Be sure to flush out high nitrogen “grow” fertilizers from your growing medium and change to a high-phosphorus “bloom” formula. Also, adding high potassium supplements for the first two weeks can help increase rapid bud development
Light Deprivation For Outdoor

Through manipulation of photoperiodism, growers can induce early flowering in outdoor cannabis plants. It is much more difficult to make the great outdoors artificially dark than it is to turn off the lights–but not impossible. Many growers have perfected the art of light deprivation, and used it to harvest their outdoor crop in midsummer, or even multiple times each year. This can be achieved by building a garden that can be covered after the sun goes down, and then uncovered part way through the morning. If timed correctly, this can lengthen the natural night to a full 12 hours of darkness. The garden must be covered for several hours each day without exception, through the entire flowering period; but the effort can bring impressive early harvests.
Spring Clones

I can’t count how many times I have received urgent phone calls from alarmed acquaintances who planted clones outside too early. Despite what anyone says, clones can do amazing things if properly grown outside. Unlike seeds, however, you need to be aware of the hours of natural light when planting outside. Because clones are likely accustomed to 18 or more hours of light, they often begin to flower once placed outside in early spring. It will depend on your latitude and the strain; but at least in California, the nights are usually too long to plant clones outside before mid-May.

By using supplemental light to decrease the hours of darkness, you can plant your clones outside as early as you like. Simply clip a florescent light with an aluminum reflector onto a stake or cage around the plants. If the light shines on the plant for even a few hours after the sun goes down, it will usually be enough to prevent early flowering. If you are afraid of late frost, you can use an incandescent bulb instead, and also take advantage of the heat it generates.
Power Outages & Light Interruption

Even with light timers and a fully automated grow room, sometimes things go wrong. If the power goes out, or you need to change lights around, keep your light cycles in mind.

When your grow room is running on a 12/12 flowering cycle, a short power outage is not a major problem. A few extra hours of darkness will not really mess things up. Of course, the plants will not grow much without light; but they should be fine for at least two days. Any longer than two days, and they will start to suffer. This will not kill them, but may cause them to become stressed.

When running on a 18/6 vegetative light cycle, a power outage resulting in long hours of darkness can trigger the plants to flower. You need to find an alternative source of light for the grow room. An electric or gas camp lantern will be enough to prevent the PFR from dropping. If you need to change things around and interrupt your normal dark period, just leave the lights on until the following dark period. A few hours of extra light will not hurt anything. Remember, you do not need enough light to keep them growing–just enough to make it not dark.

To maintain vegetative growth, use 18-24 hours of light; six hours of darkness or less.
To promote flowering, alternate 12 hours of light with 12 hours of darkness.
When switching light cycles from vegetative to flowering, first give plants 36 hours of darkness.
To harvest outdoor plants early, cut the time light reaches the plants to 12 hours each day.
To plant clones outside before mid-May, supplement with artificial light at night to prevent early flowering.
During 12/12 flowering, additional dark hours are acceptable if necessary.
During 18/6 vegetative growth, additional hours of light will not cause problems.

Successful marijuana growers know how to manipulate the environment of their garden. Once you become comfortable with light manipulation and photoperiods, the sky is the limit


Outstanding explanation @garrigan62


I have been running my autos at 12/12 they do fine on that schedule I actually prefer it after a few weeks at 18/6


Or 16/18 but they do great at 12/12


I’m on my 1st grow and started my blueberry autos @ 18/6. Around weeks 3-4 started seeing they looked weak & sickly every evening about 3-4 hours before lights out & just got more droopy near dark. As everything was good, I cut back to 16/8 and everyone seems very happy now! I know it’s been said that autos can thrive on a full 24 hour light cycle as they have the Siberian ruderalis genetics. However, wouldn’t the “full day” of sun they receive be considered anemic to a grow tent? Just a thought…

I am not sure what your problem is, @garrigan62. I literally just said the short version of the same thing you followed up with. Not sure where I went wrong?

@3high5you he just elaborated on what you said abd included photoperiod information, along with auto information. Im pretty sure i have seen him post this before, elsewhere in the forum, so i wouldnt take offense as he probably just copied and pasted it, since it is vital information. Sometimes, it takes more than just telling someone to do something. Sometimes you have to tell them “why”. Thats how i am. You can tell me how to do something all day and i may not get it. But once someone explains the “why” behind the process, i can understand and then in the future im able to implement my own system; as long as you know why, you can do many different things and arrive at the same solution!



Thank you so much, you took the very same words that I was going to say to this gentlemen… Most of my work is kept in files and it will depend on what’s going on with some ones plants that i go and choose the correct answer. I would never be able to keep up if i had to write this or any other file i may have for any one over and over again,



@garrigan62 I myself, am a gluten for knowledge. The only reason I ask is I bought the 10 for 10 sale, have grown 4 full plants so far and the only one that auto was the one I grew outside

@3high5you I wish you would reconsider how you spoke to @garrigan62 Your tone was a bit harsh.

Will has gone out of his way to help many many growers here on the forum, including me and that was not warranted! His explanations provide lots of knowledge that new growers need.


Wow, amazing in depth and so much info!! Thanks

@Hogmaster I’ve found that 14/10 is my favorite light schedule for autos. I start & end them @ 14/10 & they thrive

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4 WWA ILGM 20 for 10 planted 5/10 one has still about 3 or 4 weeks left. The other 3 were fine , smoking them right now

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I do a week 24 then second week 16-8 then 3rd 12/12 I always have something in flower so the 12-12 worked out and thrived as well