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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

72 thoughts on “Marijuana Flowering

  1. Hi

    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?

    Thanks

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  2. 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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  3. 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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    • 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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  4. ok. we took cuttings off our plants that are growing outside…they are indivieually planted and now starting to grow buds what should we do? cut em off? leave em?

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  5. Ok i have a plant that i have been growing since early september and it is still not flowering. i kept the light on it up until a month ago and niow im doin the 12 and 12 and i stil see no sign of flowering… but the plant is continueing to get full and grow tall what else can i do to make it start to flower

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  6. floweering is the most exciting stage..but u must be patient..and caring and ur plant will give back!

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  7. first timer ,My plants are outside and starting to flower do you trim leaves and fertalize they are about 6ft,looking to promote bud growth!!!

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  8. Hi! So i have a nice girl not sure how old but has been in 12/12 for about a week now. She is flowering already. I had a reflector cuz my light is facing the wrong way and it fell on her and broke a stem…. will this kill her? Also what kind of light should i use? What nutrients should i use??

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  9. …Perhaps the one major advantage Alaskan growers have is ready access to high-nutrient soil. Soil in and near river banks is particularly high in nutrients….
    That’s how they grow those giant vegetables at the Alaska State Fair!!!5

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  10. …Oh yes, almost forgot…Make sure the walls have insulation!
    Nothing kills plants faster than a sudden burst of arctic chill!!
    I understand the folks living near mountain passes and open plains regions are particularly susceptible….

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  11. To post # 44…
    If you’re in Alaska, you’ll probably want to grow indoors. Growing outdoors is particularly challenging in your region. Best idea is to grow in a greenhouse or greenhouse-like apparatus with windows that have blackout shutters. This will allow you to have darkness for 12 hours even as you near the summer solstice. Having lived in Alaska for a while, I know for a fact that blackout shutters are not in short supply…everyone has ‘em!!!!

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  12. I have a dumb question…Is it possible to grow a plant from a bung ball from the dealer? Or will that not have any seeds in it?

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  13. MistakezWeRMade

    I am growing my first plant. Its a white widow. Now it is about 4 weeks old. When should i start the flowering process? THANKS

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  14. first time grower

    yesterday afternoon we transported a 6 week old male plant out of a pot full of bitches and they are fine. its the first male plant we have found. the male plant is thriving also just be careful pulling the plant out u must be gentle.

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  15. call the station and ask comabud. this forum isn’t for you. some smokers threw the seeds. mystery solved

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  16. Coma Bud Wannabe

    Recently purchased acreage previuosly used for cattle and timber. Exploring on a 3 wheeler i located what appeared to be a corral or holding pen deep in the wooded area of the property. Appeared long time since last use but there are marijuana plants inside the wooden fence but none outside. No obvious signs of human activity so is it remotely possible the plants have been placed and left to grow on there own? They are randomly space, very tall and the leaves are very deep green. Can i get into serious trouble if the law discovers them?

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  17. southernfride

    i have an undetermined strain… its been veggingbfor a month or so under 24hr cycle… its very full and about.. 12 inches… about a week ago i switched to 12/12 cycle… so far theres no sign of preflowers… i onlly have a cheap light setup of cfls that produce 852 lumens… cant get hps’s or mh’s.. what should i do… should i let plants outdoors in natural sun for 12hrs and bring em in for 12hrs darkness…. im a lil lost… just no signs of preflowers…. should i put em under 36hr dark to help induce flowering… any help would be sweet

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  18. been growing on med card for about 3 years. this year been really hot.Need to change my light cycle. I’ve been running my lights in flower from 6 pm to 6 am but getting to hot in the evening. Been near 90 to many times. Want to change to 8pm to 8 am. should I leave them in darkness from 6 am until 8 pm then 12 hours to 8 am? Or should I leave them in darkness longer like 12 hours and then reset timer for 8pm to 8 am?

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    • You would want to leave them in the dark the extra hours. Leaving them in light longer then 12 hours/day may trick the plant into thinking its in its grow stage again and not flower stage, which could stress the plant out and effect your plants health/yield/etc…

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  19. Any tips for Alaska outside growers. From May to Sept, we get too much sunlight for the plants to flower then suddenly turns too cold. Plants use up all the energy in vegetative growth then founder and wither. Is Auto flowering of inside grows the only option?

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  20. 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?

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  21. 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?

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  22. 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?

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  23. 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?

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    • Charles Wooldridge

      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.

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  24. 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

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  25. 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.

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  26. 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 ?

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  27. 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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  28. MALE PLANT, OR A HERMAPHRODITE PLANT.. GET RID OF IT AS SOON AS POSIBLE, IT WILL FILL YOUR FEMALES BUDS UP WITH SEEDS. YOU COULD ALSO KEEP THEM FOR SEEDS, FAR AWAY FROM THE FEMALES, LIKE MAYBE YOUR ATTIC. MAKE SURE THAT WHEN YOU TEND TO THE MALES YOU ALWAYS SHOWER AFTERWARDS. YOU CAN EASILY POLLINATE YOUR FEMALES JUST FROM TOUCHING OR EVEN BEING IN THE SAME ROOM AS YOUR MALES…

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  29. hi i got plants in a cupboard on 12/12 2 weeks into flowering what should i do with the light should i change the light times or leave it on 12/12 to get the best yield?

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  30. HI guys, My friend has a small one plant setup running a 400 watt MH, and soil based grow.. Its around 4 ft atm,but being ‘trained’ to improve light coverage.Its early flowering atm,hairs on most branch colas n nodes.He wants to kno if runnin the 400MH will be ok for entire flower or is it best to have the HPS also? Thanks.. SMOKEM

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  31. my plants r about 5 weeks now im using flouresants about 3 42w each plant when going into flower i no i change to 2700 soft white but do i use more lights or will the 6 work and i would like to no if there are any light bulbs that would work light hps that dont need ballast

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  32. iv just turned 2 12\12,, what feed shud i start with been tols 2 use bloom after 4 wk ??

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    • Charles Wooldridge

      Anything bloom. First week or two go straight water, then to bloom. This gets out the nitrate. And by the time you feed them in a sense they’ll be starving, which speeds growth too.

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  33. Hello world…
    I got 2 ladies at 3 months age… they are about 4-5 ft high.. about 3 quarter inch thick stems. I put them into flowering on an 8 am – 8 pm cycle. 2 weeks into the 12-12 cycle i still dont see any signs of trichs… im runnin 1 “life glo 2 20Wa” and 1 “flora glo 20Wa”tube… also i added a UV-B lamp after going into flower stage, since it seem they produce THC to protect from damageing UVB rays. Shuld i worrie, cause i think nothing much happen to em since i start the 12-12 2 weeks ago….

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  34. hey i started from seed 20 days ago,,its about 5 in tall with 6 good leafs and lots of smaller stating,,its bn on 24)7 lite,,, can i start flowering now ?

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  35. k so i started mine with the lighting at about 18 on 6 off. how big should i let the plants get before i start the veg cycle, and what type of lighting should i use?

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  36. @juggalo

    If its got little white hairs, theyre already flowering so you need to add some food that helps promotes this and continue as normal.

    If there are no hairs present, try letting them sit in dark for 13hrs once the lights go off then proceed with your 12/12
    Knowing what strain youre growing out also helps. ;D

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  37. so i am dumb and started my plant on 12 on and 12 off how would i be able to start flowering, like what should i turn the on and off to? it is about 5 weeks old running on 12 on and 12 off and is 13 inches high, can anyone help

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  38. Aaron,

    Yes, you can transplant into new pots. It might slow growth down for a day or two, maybe not.

    Im guessing it will be worth the loss of time in terms of better yield, if it does slow it down any.

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  39. what do you do with the flowers that have seed pods do i leave alone or pull or ?i read about the heater would do it and it did will it cause a problem with the other girls.

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  40. hey just wondering my plant is in its first week of flowering and its getting to big for its pot, is it alright to transfer to a bigger pot or will that stunt the growth of the buds and produce more leaves.

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  41. Chedder – veg your plants for 3 1/2 four weeks or until u have atleast 5 to seven branches
    if your growing in a tent your limited on space so u want to think about how tall your plants are gonna get once u put them in to flower they will double in size in the first two weeks

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  42. hi,this is my first grow,iv got a 2.4mx1.2mx2m greenroom tent with a 1000w hps and a 600w hps running side by side. i hav 18 cheese plants in 11 litre pots which i got from a freind as clones. im into my second week of veg now on a 24 hour cycle.

    The plants are doing very well and all average 10 to 12 inches tall. My question is, when would be the best time to start flowering these beauts? also, I’m using special gold all mix so i havnt used any nutes yet as there already in the soil for 2 to 3 weeks arnt they,so should i even bother with the veg nutes?or just go straight into the bloom nutes?any info would be appreciated guys

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  43. Aone.aka..da strain hunter

    Don’t put a heater in with your plant the heat can stress your plant ..only if its freezeing cold plus cooler temp s…..can help your plant change colors that’s how you get some purple color on some strains

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  44. So im growing my first plant qnd it is undergoing preflowering i was just wondering how long it would take before it actually starts to bud

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  45. 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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  46. 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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  47. TheHashMaster420

    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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  48. 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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