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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. Help,jonboy says:

    Hi my sativa r just flowerin,bud,how long now til i can uproot an smoke?

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    Rating: -1 (from 1 vote)
  2. dirt says:

    what would happen if ya tricked the girls for 6-7 days?

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    Rating: 0 (from 0 votes)
  3. ODB says:

    It is the darkness that starts the flowering. Need to have the 12 hours of complete darkness. That is the best part of using the lights you can control each phase in the life of your crop.

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    Rating: +2 (from 2 votes)
  4. leanna says:

    1st time grow dont really know wot i’m doing thought i give it a try to try and save sum money, sum plants have started budding with natrue lighting but most have not and showing no sign of this and im sure they are female, do i need a light to help budding or is it the darkness that make them flower. please help 😉

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  5. TheHashMaster420 says:

    As long as your temps don’t drop below the 60’s or go above 90 degrees F you should be fine. You’d have to live at the northpole or south pole for this to be a problem during April!

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  6. john says:

    Put a heat sorce in there.dum dum.

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  7. justin says:


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  8. […] need to grow tall and strong to prevent being shaded out. Sativa strains tend to take longer to flower than Indica strains, sometimes over 13 weeks, and this is an adaptation to a long tropical growing […]

  9. mike says:

    but with the lights off it makes the room temp cooler then what do you do so the plants wont get cold and die.

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  10. […] Morning Glory cannabis seeds from Barney’s will produce a Sativa dominant plant with some of the great Indica traits thrown in for good measure. Morning Glory cannabis plants are well formed with long stems that will support huge buds, forming dense kolas along the length of the stems by the end of the flowering period. […]

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