Marijuana Flowering & Light Cycles

Flowering marijuana is when a female marijuana plant starts to produce buds. Although there are both male and female plants, the majority of people will be looking for female flowers, as only females produce the prized buds you eventually smoke.

This section will take you through the basics of the marijuana flowering stage: from when to begin the marijuana flowering cycle; how long it will take; what marijuana light cycle to use as well as more advanced advice on nutrients.
Marijuana Seeds Flowering

When is your marijuana plant ready for flowering?

Marijuana doesn’t flower because of size or age; it’s to do with the light cycle the plant is on. When you flower your marijuana plant is entirely up to you. It is recommended that you do not start flowering until the plant has been in vegetative growth for at least 4-5 weeks and has shown pre-flowers. A good time to bring the plant into flower is when it has reached ½ the size you intend it to be as during flowering, a plant will grow 2 – 2 ½ times its vegetative size.

Marijuana Flowering Timeline

Depending on the type of weed you’re growing, the marijuana flowering stage can take anything from 6 weeks for a short flowering Auto strain, 7 – 10 weeks for Indica dominant strains and 10+ weeks for the Sativa dominant strains.

The following guideline gives you an idea what to expect during flowering. This is just a rough guideline as flowering times vary from strain to strain.
Female Pistils
1-2 weeks – After switching to 12/12 marijuana light cycle, your marijuana plant will start to show its first flowers.
Flowering Week 5
3-5 weeks – Plants start to stretch for light and flowers will appear at the nodes. Your plant will start to develop creamy white pistils from its flowering points. New flowers will continue to develop over this period.

5+ weeks – The buds start to thicken significantly. Flowers will close and the calyxes will swell. Your leaves will yellow as energy is put into making the flowers. During this time, your plant will reach its flowering peak, with pistils swelling and finally changing in color from white to amber, moving on to a reddish brown.

Final 2 weeks – For the final 1 to 2 weeks of flowering you will want to flush your plant. This means use nothing but clean water.

Final 48 hours – You can further flush the nutrients and unwanted sugars from your flowering weed by turning out all light. The plant will utilize the sugars already produced during photosynthesis to continue to swell the budding points.

What are the types of flower?

As a grower or breeder of marijuana, you are able to produce a variety of plants depending on your growing needs or preferences. Plants grown from seed can take on the following forms, depending on the seed genetics.

Female – A female plant is the main aim for most growers. Females produce the heavy, THC covered buds that are eventually harvested, cured and smoked. If fertilized, female plants stop high THC production and start seed formation.

Sensimilla – Sensimilla is the term used for marijuana flowering that has NOT been pollinated by a male plant. A sensimilla flower is the most potent, carrying the most THC and is the most prized for commercial cannabis growers.

Male – A male plant doesn’t produce the buds you smoke, they produce pollen that can be used in seed production. If you wish to grow unfertilized female marijuana plants, a male in the growing environment will pollinate your Sensimilla unless removed.

Hermaphrodite – Hermaphrodite plants occur through stress during vegetative growth or early flowering. A plant that has been left to flower for too long can also hermaphrodite. Hermaphrodites can still produce smokeable buds, but they lack the potency of a Sensimilla plant.
Types of  marijuana flower

Marijuana Light Cycle

Indoor Growing
To start your plant flowering when growing indoors, you need to mimic the lighting conditions found in Fall/Winter. This means taking the plant from the 18/6 marijuana light cycle used in the vegetative growth stage, and changing it to 12 hours light/ 12 hours darkness. You will also need to reduce the number of lumens you are giving your plant. This means changing your bulbs from a summer sun replicating 6500k, to 2700k which mimics the warm red sun of fall. As marijuana is a fall flowering plant, the shorter light hours and red light reproduce the conditions in nature. Be careful not to make this change before the plant has shown its pre-flowers as this will stress the plant and may cause it to become a hermaphrodite.
Marijuana Light cycles

In the dark period, it is essential to make sure your grow room is completely light free. Light within the dark period will prolong the amount of time it takes for the plant to flower, reduce its output and put unnecessary stress on the plant.

When grown outdoors, marijuana plants enter the flowering stage when the days start to shorten. This generally means weed plants go into flower in fall as the life cycle of the plant reaches its natural end and the female plants become pollinated. However, left unpollinated, female plants start to vigorously produce THC and resin as the plants energy is used to produce buds instead of seeds. When growing outdoors, nature takes care of your marijuana light cycle and brings your plant into flower naturally.

During marijuana flowering, plants need a different set of nutrients to produce bigger buds which in turn produce a bigger yield. Marijuana flowering nutrients are higher in phosphorous (P). It is linked with resin and seed production. Recommended levels are 5-50-17 (N-P-K), but you can use 15-30-15 or 10-20-10 and still get satisfactory results. Follow the manufacturer’s instructions to avoid nutrient burn and to get the most out of your nutrients.

Associated Problems with Marijuana Flowering

Most problems associated with marijuana flowering can be found below:

Mold – Mold is likely to occur when the humidity in the grow room is too high. This can be avoided by measuring humidity and avoiding spraying your plants.
Mouldy Bud

Pests – Pests normally come from clones and are rare in grows that have been started from seed.
Spider mites

Hermaphrodite due to stress – This can be caused by light leaks or starting your flowering light cycle before pre-flower. Stress can also be caused through either too much or too little water, as well temperatures being to high or low. Hermaphrodite plants may spoil other plants in your grow room by releasing pollen.

Light leaks – causes stress on the plant and leads to a slowing down of the flowering process. Also, causes plants to hermaphrodite.

Over ripe bud – Caused by not harvesting in time. A late harvested plant will not be as potent and will run the risk of becoming a hermaphrodite.

Male plants in the grow room – Male plants will pollinate your female plants, leading to all the energy that is used to produce resin heavy buds being utilized to produce seeds meaning the plant produces a weaker and smaller yield. The moment you see that you have a male, remove it from you grow space and destroy.

The marijuana flowering stage is one of the most important steps in the growing process. Making sure you put your plants on the right marijuana light cycle will yield the results you want. The guide above provides all the information you need to successfully flower your plants.



50 comments on Marijuana Flowering & Light Cycles
  1. Dan Scury

    I have a question about flavor. Virtually none of the store bought buds have that spicy flavor. My plants are outside. I noticed that the budworm damage has the great flavor I remember. My conversations with the store folks about flavor does not seem to connect. They let me smell the buds, but i tell them they all smell good but have no flavor. Is flavor and THC strength inversely related? It seems to me that the budworm damage maybe 1-2 weeks old. So does that mean the best flavor was 2 weeks ago?

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  2. Rob Humphrey

    Does anyone know the exact minimum amount of daylight required for og outdoors to start the bud process?

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  3. Chris

    Why have my plants started budding. What do I need to do ?

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  4. Green Man

    It depends on the strain and flowering time. What is it you’re growing?

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    Rating: +5 (from 9 votes)
  5. tomalock

    You can take that “bud clone” after it has rooted and begun to grow on it’s own, by the way you did the cloning process with lights cycle perfect, and put it back under 18/6 and that bud will revert to it’s vegetative state and produce several new shoots like a tree stump does.
    I take pieces of wire pulling over the 4 best new shoots and trim off the others, it depends on the strain how long you leave it under 18/6 cycle but depending on size of container (3gal sized) I’d say 2-3 weeks depending how how fast the new shoots grow.

    I start my plants outside from seed, make a fall harvest then on the inside buds that do not get as much sun light have a chance to grow more then they are cloned to reveg inside for a winter harvest, every year and it works like a charm and the quality is excellent.

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  6. vicki gailey

    Question, my plants have started to flower, should l use fertilizer and how long. How long does the flower stage last. I see the white pistons, with leaves. When n do l harvest the plant????.

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    Rating: +9 (from 51 votes)
  7. Meryem

    Wow is my first time growing and I am so lost more now then went I start it I am now I the flowering stage on day 64 but I see the pistils change color to darker but not completely I still see some pistils little white and I am not sure when to harvest at least one of them the true og fem… I read 67 days in flower it should be ready but I don’t know I just don’t want to harvest before time I will Appreciative if you could help me out ty so much :)))

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  8. mike

    when using auto flower seeds,do I still feed the plant with potassium or any other feeds?

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  9. sweetleaf

    Did my first grow in over 34 years, for cbd use,edibles and tea for pain( quit the doctors,hydrocode) and going at it naturally.
    the first plant is perfect,4 more started.
    used auto flower seeds, it’s too easy compared to 3 decades ago

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    Rating: +1 (from 7 votes)
  10. scotster

    help My first grow .im growing indoors 1ooow hps I have three plants in a tight space 3x5x7 tent 1 is flowering sativa the others are indica and are not .how do I get the two to flower ?????

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  11. Pat Sakaba

    If I do not want my femail plants to pollinate from my male plant, I far away should I separate the female from the male?

    When can I start harvesting my male seeds?

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  12. mike

    I Am a new grower And have 6 plants outdoors and are around 3 foot tall. Want To start flowering can I use black garbage. To start the light cycle

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    Rating: -20 (from 70 votes)
  13. bruce hoffman

    looking for seeds that will help with M S pain
    can not find the right seed I do not want to smoke
    we need make edibles
    we have been growing hydroponic vegetables for many years

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    Rating: +4 (from 16 votes)
  14. luke

    ok this is a BIG question and ive been doing a lot of research and have come up short this is my 2nd plant ever but these are my first set of clones. ok… I had a plant that was about 5 weeks into flowering and I had a few smaller branch at the bottom that were not getting enough light so I decided to take 2 clones from this plant at this time. so I cloned the already small budding branches… completely natural let me add. but they stayed in my grow room witch was on a 12/12 light cycle. it took a couple weeks but they started to start producing extremely frosty leaves. HERE IS MY QUESTION… CAN I LEAVE THESE IN FLOWERING….WILL THE PRODUCE AN ACUTAL GOO SIZED BUD OR DO I ACTUALLY HAVE TO PUT THEM BACK INTO VEG STAGE BEFORE RETURNINH THEM TO FLOWER……..PLEASE HELP

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  15. Scott

    If I am growing an auto flowering plant do I need to change the light to 2700K when it begins to flower?

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  16. Yesenia

    Can I do about my plants that are growing seeds week 4 to 5 they are budding really nicely but I just noticed some seeds ??

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  17. Yesenia

    What can I do about plants that are seeding can I add ammonia to stop the seating or is it too late week 4-6

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  18. maurice merritt

    If u have a female and a male in the same pot how strong will ur female be

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  19. cizzle

    I have an outdoor female ” dutch treat ” plant that is 4 ft tall and starting to bud . I have n o idea how to clip the buds or when the proper time would be . please help I don’t want to massacre it :/
    I also have a female kush plant and a few other strains all outdoors that someone had given to me . they are all beginning to bud but still look like they have a ways to go . im thinking that by the time summer weather is completely over that they will be ready ..if not I don’t know how well they will turn out due to the rainy season starting soon ..I would apprechiate any tips , although this sight has already helped a lot I want to be positive on everything I need to do prior to so I can ensure as much harm reduction as possible .. anything helps
    thank you !

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  20. mattymac

    My plant is outside its flowering about 4/5 weeks. I haven’t. Used nutrients will nature take its own coarse and bud itself or should i do anything to help it? First time grower need advice asap PLEASE!!!!!!!(

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  21. Dabidabeedab

    Sinsemilla is the right spelling. From Spanish (Sin = Without; Semilla = Seed)

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  22. mike

    First sighs of flowering you will not see.Water consumption growing twice even three times bigger is a first clue.After a first week of bigger water consumptionweek creating of new leaves is much more dense and compact, leaveas growing beetwen new branches much more efficient to vegetative stage.Pistil females are occuring on the youngest leves ramifications.If you are good observer you should notice it almost immediately.

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  23. Keri Tucker

    I’m interested in growing between four and six plants how much light what I need and how many different lights dinette one for flowering and one for the budding stage and I really didn’t want to spend over two to $300 what would you recommend

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  24. richness castro

    hi their I get to the flowering stage and the leaves start to curl is it the watering schedule or the air I’m just starting out I master out door growing now in trying the indoor I have 600 watt led light in a tent .

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  25. roncheechong


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  26. Jayy

    I planted 8 Blue Dream strains so far. 4 are a few weeks older and already started to grow about 3inches.. They’re in plastic red cups on my windowsill but I’ll move em to a bigger pot when they get lil bigger . I open the window to let the air out, give em water when they seem dry and i use the sun as a light source. It’s my first time and I have no idea what I’m doing.. Any tips on how to keep the plants healthy using nutirents…?
    Thanks in advance ! (:

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  27. Jbw

    What is the best outdoor strain and diases resistant to grow in South Carolina with huge yield. Wat is the most reliable seed company yo order from

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  28. Dylan

    Hi my flowering stage is week 5 coming into week 6 my plants look like hermathrodite pics on yours but some of the White flower not a lot atm are just starting to turn Amber is my plant normal or an hermathrodite pls help

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  29. teresa

    Hey greenman can pruneing to much when plant is in budding stage cause it to go to seed?

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  30. emmett

    am growing 1 plant it has pistils comein out of it now but doesn’t seem to be growing any more will it be long b4 they start bubin lots of crystals over it is that a good thing am a first timer at this any help would be great

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  31. DBLAZE


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  32. ChicaJayne

    I’m on my first grow and am using LEDs for flowering. My Durban Poison (1) has been flowering in its 42″ x 46″ flowering area for about 3 weeks now and appears to be doing well tho it took a while for me to get the temperature and light schedule consistent, as I’ve added both a CFL and heater without a timer. Any way, the LED in use has switches enabling me to use red, blue, or white lights or any combination there of. All three colors have been running 12:12 up to now (3 weeks) but I am wondering if color adjustment is needed. I am planning on adding 2 more cool white CFLs to the lower back region as it is becoming thicker and denser tho a few leaves have fallen off back there. I’ve tied many branches down and am unsure if I should untie them to turn the plant … heck, I’m not even sure how I can move it to flush nutrients at this point. She appears healthy and strong; I, on the other hand, feel my learning curve is more like a tilt-a-whirl ride. Your advice would be appreciated. … Oh, she’s in soil.

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  33. cris

    seeing if i can get some help. like during the final flowering stages will the plant tend to loose most of the leaves? it started out normal as said above would turn yellow as the energy is pushed from them into the buds but my plant is pretty bare now. has lost almost all of the leaves and still has at least another week or two before the trichomes are expected to be about a 50% mix cloudy/amber. any input or advice?

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  34. Jaybird

    How do you show case a new strain… G-13+laughingbuhda+afghan(1980s) . The flowers do things never seen in 26yrs of growing. Genetics speak for themselves.. Just might be the next Cup Winner.
    Thanks, Jaybird.

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  35. janice-leigh

    I’m a first time grower been doing some research and ive made a small grow tent with myler lining I only want to grow 1 plant to start So wanted to ask what light or lights would work cheap as pos and do I needs fans to just grow 1 plant thanks in advance xx

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  36. terry208

    Why is total darkness so important indoors when outdoor plants get all kinds of light at night? thank you

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  37. Green Man

    The flowering time in the description of a marijuana strain is referring to the amount of time the plant needs to flower. After the flowering stage the plant will be ready to harvest.

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  38. Deb

    When it says flowering time in description, is that when they start flowering or should be finished?

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  39. larry

    when growing auto flowering plants indoors grow boxes do ya use grow bulb first or flower bulbs all the way thru thanks

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  40. Green Man

    You need to be careful about pruning the fan leaves once the plant has started to flower. There is a difference of opinions on this but generally we wouldn’t recommend you trimming any fans leaves once it is flowering as it is these leaves that promote growth in the buds. It is ok to remove leave towards the bottom of the plant during vegging as this stimulates growth.

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  41. donna morrone

    I have 2 outside plants that are in the flowering stage. Can I trim a few of the big leaves during this stage to allow the sun to get to the flowers under them. Is that something I should do to yield larger buds??

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  42. Green Man

    Getting you’re marijuana lighting cycle correct, ensuring you’re using the correct color light whilst flowering and giving the plants bloom nutrients will ensure you maximize the potential of your marijuana plant when it’s flowering.

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  43. paul eriole

    what is the secret ingrdiant to help pot flwer better

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  44. dave sobczak

    the info you have on this sight really comes in handy

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  45. julie

    TELLME…I will be growing 12 white widow feminized,what size tentt,how many not an option.

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  46. Nathan

    Any tips for plants that have gone from indoors to out, I live in the desert and the house is swamp cooled causing major humidity proplems. So the plants are basically at the week 5 stage of flowering and I’d like to know when I can expect to harvest as the days are longer but the plants have already begun to flower and I’ve manged to keep them in an area with a limited time of consistent lighting each day under the sun what can I do to prevent hermaphroditism and pests? Damn squirrels.

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