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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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From the forum

How to Grow Marijuana Forum - Growing Marijuana Indoors & Hydroponics

111 thoughts on “Marijuana Flowering

  1. maria says:

    i wanted to also ask. was told to cut off all big fan leaves while plant blooms so more energy to blooms, but also read not to cut them off??? which is correct?

    • Kc says:

      Id say dont cut off any unless there dead or dieing, there are small leaves all over the nug but the fan leave absord a lot of energy from the light and the nug itself(just my opinion) doesnt absorb as much or if any energy.

  2. maria says:

    have flowers w/long stigmas, white. now, a few are changing to lite brown. do i wait till most are brown or harvest before they turn too brown?

  3. Badger says:

    How did you get on John?

  4. tank says:

    Has anybody heard about putting your plants into a dark, cold room (40-50 degrees) for the last three days or so before harvest? Ive heard it puts the plant into “survival mode” and pushes all nutrients to the buds making them swell and producing a much bigger yield. Thoughts?

    • Justin says:

      No do not drop temps you could kill your plants ppl will do that to create a false purp but it will significantly drop thc content

      • gprippers says:

        YOU DEFINATELY WANT TO PUT YOUR PLANTS IN THE DARK THE LAST 48 HOURS AS IT USES UP LAST OF CHLOROPHYL THAT WE ARE TRYING TO GET RID OF AND COLD TEMPS WILL PURP EM UP A BIT. YOU SHOULDNT FEED THEM AT ALL THE LAST 2-3 DAYS PRIOR TO PUTTING THEM IN THE DARK AS WELL AS DRYING THEM OUT STRESSES THEM OUT AND ALSO BOOSTS OIL/THC PRODUCTION. OF COURSE WE ARE KILLING PLANTS THE LAST 48 HOURS IN THE DARK AS WE WANT THEM TO DRY UP, DUMP CHLOROPHYL AND IMPROVE TASTE AND SMELL. READ THE SCIENCE BEHIND SIMMS WHICH DOES TESTING FOR THE BIGGEST GROWERS IN HOLLAND ETC AND THEY STAND BEHIND EVERYTHING I JUST TYPED!

  5. FarmerSteve says:

    Hi Guys, I’ve got clones about 3 weeks old growing well,I’ve just been told that the plants I got the clones off have started growing balls!what are the chances my babies will be hermos as well? Should I g
    Get rid and start again or wait and see?

    • Charles Wooldridge says:

      It depends, if you want to grow from the seeds it works great as you’ll have buds and seeds too. But if you want only females you’ll have to do some sexing which takes 2-3 generation of plant. Or start over. I would grow them and find another strain to sex with, then put in veg state and leave in veg state. Now you have a (mother) plant that you can pull up to 30 clones off from over period of lifespan.

  6. str8cash says:

    yo will putting my crop str8 to a full 36 hours of darkness before switching to 12/12 help the flowering process and does feeding in darkness have a negative impact. super lemon haze

  7. Badger says:

    Jamie, if the plant is outside in natural sunlight it will flower towards the end of the summer when the length of the days begins to shorten. If you are in the northern hemisphere you can expect a harvest around October, depending on the strain of weed you are growing. If it is in the earth in good sunlight you could get a better crop than you would with an indoor hydro grow.

  8. jamie says:

    can it flower with just 12 on 12 off but i mean with just sun light ?

  9. jamie says:

    hi iv got a small plant about 3 weeks old i can already tell its female i have always had it outside only give it abit off water every couple off days its about 5 inch tall how do i make it flower when its ready ?

  10. John says:

    I tried switching my nutes to a bloom nute once I went 12/12 prior to a preflowering or sexing…this is not smart..plants got droopy and did not respond well. I went back to a 2/2/2 mix and they are healthy again. Wont use bloom until real flowering begins. Also, I have my lights come on at night and off during the day….this keeps the tempature constant as outside heat warms during dark cycle and lights warm during light cycle. My smallest plant is 2′ tall and my biggest is 4 1/2 ft tall. They have all sexed female (I used the guide to choose which random seeds would be female seeds and it seemed to work) and are starting to preflower already. Will switch to bloom nutes next week and repost when I have new results.

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