Basically: Flower Light Cycle is 12 hours on and 12 hours off and the Veg Light Cycle is 18 hours on and 6 hours off.


  1. I have reverted plants that were in the flower cycle for up to 3 weeks back to the veg cycle with no problems other than losing time.
  2. All you have to do is change your flowering light cycle of 12 hours on and 12 hours off to 24 hours on for about 10 days.
  3. Your plants will start reverting back to the veg cycle.
  4. You will see single leaves starting to grow out of the buds – that’s normal –
  5. After 10 days, change the 24 hours on back to the vegetative lighting schedule you use, we use GLR
  6. Be very strict during the off hours – allow no light to come in – don’t open the door – be patient!


A time consuming task but one that has to be done, is figuring out the males from the females when you’re growing from regular seed. We’ve been growing weed for over 40 years and still can’t tell a female from a male until they flower for a week or two.

IMO-growing from regular seed is better than using feminized or auto flowering seeds. Regular seed will give you a larger, more robust plant that you can easily clone.

Many growers can tell, or at least claim they can spot a girl from a boy and there are many articles and videos about it, but we can’t figure it out. So we’re stuck; when we grow from seed, we have to allow seedlings to grow for awhile in the vegetative cycle than start flowering them (switch from 18 hours of light to 12 hours of light) so we can figure out who’s who.

After you switch your lighting schedule to 12/12; to tell a male from a female, look for little balls (male plants) that start to form and get rid of those plants, (we do save one to pollinate 1 female for seeds).  Sometimes the little balls start forming in a couple of days and sometimes it takes a week or two.


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Now we have to switch back to the vegetative cycle


Once we have our girls (they have white wispy hairs/no little balls) figured out, we change the flowering light cycle back to the vegetative cycle. We start with 24 hours light for about 10 days then switch to the GLR.

You’ll notice weird looking single leafs growing up through the little buds. Don’t worry about them, just pick them off if they make you nervous or leave them.

After 10 days of 24 on, we change back to our normal veg lighting schedule, we use the GLR (Gas Light Routine) for the remaining time in the veg cycle (now you can see why clones are so much better to start with).

Even though the plants initially look a little weird, they grow out into normal looking plants in a short while. Once you have a group of female plants growing in the vegetative cycle, you can start taking clones when the lower branches get to be around 3″ long or so.

All in all it can take around 3 weeks to differentiate the boys from the girls so it makes a lot of sense to keep a mother plant growing so you can take female clones anytime you need them.

    13 replies to "How To Change The Flowering Cycle Back To The Vegetative Stage or Cycle"

    • Jayme M

      Great article.
      Do you have to give them 24 hours of the first 10 days or can I do 18 hours ?

      • press

        Hi Jayme,

        Thanks for stopping by.

        Every time I’ve reverted a plant I’ve put them under 24 hours of light.
        The first time I did it because it made sense to me and I’ve done it a ton of times since all successfully.
        I haven’t tried 18 hours but in all reality it should be okay because it’s the normal VEG hours.

        If you want 18 hours to save a few bucks on your energy cost I advise to bite the bullet and run 24 hours because I think they revert a bit faster.
        If you want 18 hours because it’s more practical for your situation then by all means it should be okay.

        Thanks again for stopping, I’m always around.

      • press

        Hey thanks by the way!!!

      • The noob

        18hr on 6hr off or 24 on and ? Off, I just want the perfect info for reverting a flowering plant come on guys , your not Being precise you know there is retarded people out there listening to you guys

        Me , the noob who grows in freakin tents

    • Gary Edward White

      no matter what timing I use I have pre-flowered every grow. Some revert some die, they’re all screwed up. None of the suggestions have helped me. (outdoor) I don’t use any artificial light, I start the first day of spring with Fem. seeds and they pre-flower every year. Can’t stop it.

      • press

        Hi Gary,

        Thanks for the comment.

        When growing outside, Mother Nature takes care of flowering. There isn’t any timing unless you’re doing something like moving the plants in and out of the sunlight yourself.

        For example, where I live in the mid west, when I start a plant outside at the end of May, it will grow in the veg cycle until about the middle of July then the plant starts to flower because it detects the change in light; the days start getting shorter. Then it grows in the flowering cycle until harvest.

        You said your plants pre-flower every year; what do you mean?

        When you plant your seeds in the spring, they shouldn’t start flowering until around the middle of July.

        Are you using auto-flowering seeds by any chance?


    • Tim

      Why don’t you just take a clone from each plant during veg and flip the light cycle on the clone? Ta da, you just sexed each mature plant.

      • press

        Hi Tim,

        Thanks for the comment.
        Absolutely, you can.
        Great idea!!!

        I’m too lazy.
        Do the math; time wise which works faster?

    • Jeff Parker

      I read your article. Thanks for sharing informative content. I really like your excellent content.

    • kevinjoseph

      Thanks for the article; I really like this post it was excellent and integrating post. The period of growth between germination and flowering is known as the vegetative phase of plant development. During the vegetative phase, plants are busy carrying out photosynthesis and accumulating resources that will be needed for flowering and reproduction.

    • Sam Evans

      i took my plants indoors due to the wet weather we have. bud rot is huge in mass.. i put into a room and lights are on a schudule to run at night to save cost. question: will a 24 hour, 1 day light change be a bad thing during the flowering last stage…

      • press

        Hi Sam,

        Thanks for stopping by.

        If I understand, you brought plants inside that are presently flowering into a room with existing 24 hour light and you are going to take them back outside in one day.

        How close are they to harvest? If they’re outside plants, you should be pretty close right now.

        If you only have a week or two until harvest, one day shouldn’t hurt.

        If you have longer to go, 3-4 weeks or longer, especially if they are grown from auto-flower or feminized seed, I wouldn’t mess around, keep them dark tonight somehow as they are super sensitive to everything and will start to morph in a blink of an eye. Morphing is not good.

        Thanks again for stopping, I hope I was helpful.
        I’m here tonight if you need me (watching and hoping the Yankees lose). LOL


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