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Marijuana Flowering

Marijuana Flowering

If you want your marijuana plants to start pre-flowering just change the light cycle to 12 hours on and 12 hours of complete darkness. This convinces the plant that the days have got shorter and now is the time to flower.

Why does this work, well let’s think about how plants are in their natural environment. Marijuana like most plants start off growing from seeds in early spring, then go through their vegetative stages in the later stages of spring and all of summer and when fall comes and the days start to become shorter during fall/autumn there is less light and more darkness and this triggers the plans to flower, or bud. So when you are growing indoors professional growers move from a 24 or 18 hour vegging light per day to 12 hours on and 12 hours off.

pre-flowering female marijuana

Although, while waiting for marijuana to flower can seem to take forever, once your plants truly enter the flowering stage their growth rate can be stunning. Growth patterns and nutrient cycle timing and requirements will change. The vigorous vegetative growth will slow, stems will elongate and flower formation will begin rapidly at first before slowing. If you are growing hydroponically you should now be using a bloom or flowering mix of hydroponic nutrients. If you are growing in soil you should add a fertilizer that is high in phosphorous and potassium such as ‘Super Bloom’. Read more about marijuana nutrients.

Whilst in the flowering stage it is important that plants receive no light outside of their 12 hour day cycle. Any light received can confuse and stress plants leading to abnormal growth. Make sure the room is light tight. More information on marijuana lighting.

  1. Note that less than 12 hours light will reduce flowering speed and overall yield.
  2. Note that putting the lights on during the 12 hour dark period a number of nights in a row, even for a few minutes can revert the cannabis back into its vegetative growth cycle.
  3. Trick you can use a green light bulb in the grow room to help you work while the cannabis is in darkness. Green light will not affect the plants.
  4. Trick some growers will give their babies a full 36 hours of darkness to send the message that flower must begin. This usually decreases the time in which flowering begins.

These days you can also buy auto-flowering marijuana seeds that will start to flower after a certain number of weeks.

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114 thoughts on “Marijuana Flowering

  1. Charlie says:

    I have about 25 plants (outdoor) … all are looking good except one that is covered with little yellow flowers. I assume this isn’t good. Should I just remove the whole plant? (I’m a first timer).

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  2. If people only knew the real laws on marijuana and hemp, America would be doing so much better. No victim no crime! Every stoner should know how to challenge jurisdiction in a court room to get any victimless crime case dismissed. Television and entertainment are too distracting though… people have been tricked.

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    Rating: +5 (from 13 votes)
  3. KEM$ says:

    Yea I’ve been hearing everyone puts there plants on a flowering cycle of 12/12 I put it on a 16/8 & get a good reaction

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  4. Marie says:

    Hi I have 3 pineapple Express plants about 9 ft tall they are outdoors planted6/2015 it’s now Sept 1 they haven’t started to flower yet what can I use to help them out,Can I use Scott,super bloom if so how much I have them in wine barrels.Thank you from any help.They are healthy too.

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    • Gerry says:

      If you’re growing them outside, cover the plants with tarp or even huge garbage bags and cut the light exposure to 12 hours of light & 12 hours of dark…after about 4 to 10 days, you should start to see white hairs or what looks like small bunches of green bananas. If you see balls or banana bunches, kill it…unless you want seeds. You also could shorten the process by keeping your ladies in complete darkness for two full days or even longer. The plants will turn yellowish and whitish, but they’ll be just fine. Why you’re not seeing the sex of each plant is due the amount of light they’re getting now. Cut the light to 12/12, and you’ll soon see results. You owe me a doobie for this Marie…just sayin’. Take care.

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    • ty says:

      hock them with nutrients or put a ventilated tarp over them for tw days let them breath at night though, you got to shock them, anything from the store that says flower bloom or buds, organic fish shut basically. I just got my big buds to start budding I was scared they would t. But good luck sit.

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  5. Noel says:

    Ok, so im growing my plant outside and my main flower on my plant has just broke is the plant still good?

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    • Gerry says:

      When my plant would break, or a branch would break off somehow, I’d put biological tape on it…even electrical tape works, but the biological stuff leaves no gummy shit. The plant can take a beating and survive Noel. Some folks even deliberately abuse their plants to induce stress. No worries dude..just bandage up the wounds. They heal just like bones do.

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    • Josh Strout says:

      Yes just put something solid like a popsicle stick and wrap it with green wire from the garden section and it with fix it self.

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    • 420guy says:

      Oh ya it sucks the flower broke cuz it privy would have got a lot bigger but oh we’ll now u can test it wile u grow an when the hairs r 70-90% orange pull the plant or when the crystal/thrichomes are milky white or almost Amber colour if they are clear still they aren’t ready use a magnifine glass to check it out also 2 weeks before there done don’t give them any fetilzer or nutrients it will wreck the taste an problem isntt healthy lol

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  6. Sean says:

    First time grower I have 2 plants there both showing yellow leaf at the bottom of the plant there both the same age 4 months old there out door is there a way to push them to flower? But the real question was why do I have yellow leaf at the bottom of my plant

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    • Gerry says:

      Try mixing piss with water and feed it to the yellowing plant…seriously. Piss is nitrogen pure…either that or give it Nitrogen nutes in the form of fertilizer.

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    • James says:

      yellow leaves can mean not enogh nutrients. Grow indoors and you get a faster process. But less bud outdoors more bud.

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    • Salubrious Sal says:

      Leaves get older and lose nutrients. They’ll fall off. Their photosynthetic chores are completed!

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      Rating: +3 (from 3 votes)
  7. Heya says:

    Hello i want to ask if i can start growing from seeds that are in my bought weed from the dealer ?

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  8. Letmeknow says:


    Have been in the 12/12 stage for 6 weeks and all I have is a lot of seedling pods all over my 4 foot high branches. Why do I have all these seedling pods? What can I do to move it to a true flowering stage?


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    • GameChanger says:

      Throw plants in 12/12 light cycle with HPS lights
      First time grower Best Nutes to use it GH
      3 part or nova series.
      Follow the directions on the back….
      Feed around 1000ppm in beggining of flowering.
      each day is different.. monday you should Feed.Tuesday Water, wednesday wait. thursday Feed ect…
      This is a great diet plan for your plants.
      you can always add bloom boosters to your feed .. make sure your ppm is never higher than 1300 in beggining of Flower.
      Week 5-8 ppm’s can up to 1500.
      Make sure you start flush end week 7 for about 2 weeks..
      Flush plant until Water run off read below or between 150ppm and 300ppm
      when plant is done cut it down and dry in same area or something simalar.
      Dry until stem cracks..then throw it in a jar opening 2-3 times daily. keep jar in a dark place.
      If your bud looks and Taste like crap, theirs no 1 to blame

      If anyone would like to add to this please do

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    • Kc says:

      You sir most likly have a male plant or maybe a fertilized lady depends on your set up and where you got your seeds

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  9. Mike's reason says:

    I am a first time grower. I am having problems sexing the plants. My plants are growing little leaves where the stems meet. The last batch grew seed pods during flowering stage.

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    • Amber says:

      Hey! Just get feminized or auto flowering seeds! I got Narcotic Kush. So, all I did was pop it in good soil mix,water, wait…boom! Two days!Germination! I got my big metal halide goin’, she is a beaut! Shorr and super full, we are at the preflower/flower stage!
      No sexing, no guessing, no worries! AND she coukd reach 22percent THC. Pretty fine for an auto!
      IRecommend plantin in whatever she’s to grow in.
      Gonna do an auto N. lights next!
      I know it’s a bit lame, but, I’ll get ro the sexing and all, right now, I just don’t wanna pay 300 for what I can grow for 30!

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  10. tommyhawk85 says:

    1st time grower, long time smoker. I have a 3’hi x 2’wide x 10”deep hydroponic box. reflective liner. I have 3 female plants about 6” after 7 weeks. fairly bushy I’d say. I think they should be taller. maybe not. should I start the flowering cycle? my ladies are on a 18-6 cycle now. I’ve been reading the posts and some of them read like russian to me. any help would be appreciated.

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    • Jandyweed says:

      Sound awful short for 7 weeks – what are you feeding them?? I was having problems and took others advice and switched to GH Flora 3 part series nutes. Have not looked back – 4 week old girls were 2 foot tall – changed lights to 12/12 and in a week they are nearly 3 foot with heads beginning to form already – BEAUTIFUL. I’m using a new home made small scale flood and drain system – its the best. Hope this helps Cheers

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    • Jamal says:

      Its up to you Tommy. Remember that they will stretch a bit during flowering so with such a short box maybe it is time to flip them. I would normally wait a bit longer, but do not have the same height restrictions as you. 3′ height space + plants + lights doesn’t leave you much room. So yeah, flip them now.

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