Marijuana Flowering Guide

The the plant will be induced to fruit or flower with dark cycles of 11-13 hours that simulate the oncoming winter in the fall as the days grow shorter. As a consequence, it works out well indoors to have two separate areas; one that is used for the initial vegetative state and one that is used for flowering and fruiting. There is no other requirement other than to keep the dark cycle for flowering very dark with no light interruptions, as this can stall flowering by days or weeks.

Once a plant is big enough to mature (12? or over), dark periods are required for most plants to flower and bear fruit. This will require putting the lamp on a timer, to create regular and strict dark periods of uninterrupted light. In the greenhouse, the same effect can be created in the Summer (long days) by covering it with a blanket to make longer night periods. A strict schedule of covering the plants at 8pm and uncovering them at 8am for 2 weeks will start your plants to flowering. After the first 2 weeks, the schedule can be relaxed a little, but it will still be necessary to continue this routine for the plants to completely flower without reverting back to vegatative growth.

Outdoors, Spring and Fall, the nights are sufficiently long to induce flowering at all times. Merely bring the plants from indoors to the outside at these times, and the plants will flower naturally. In late Summer, with Fall approaching, it may be necessary only to force flowering the first two weeks, then the rapidly lengthening nights will do the rest.

Give flowering plants high P plant food and keep them on a strict light regimen of 12 hours, with no light, or no more than a full moon during the dark cycle. 13 hours light, 11 dark may increase flower size while still allowing the plant to go into the flowering mode. Use longer dark periods to speed maturity toward the end of the flowering cycle if speed is of the essence. (8-10 days) This will however, reduce total yield.

Two shelves can be used, one identical to the other, if strictly indoor gardening is desired. One shelfs lights are set for 12-13 hours, and one is lit continuously. Plants are started in continuous light, and are moved to the other shelf to flower to maturity after several weeks. This flowering shelf should be bigger than the “starting” or “vegetative” shelf, so that it can accommodate larger plants. Or, some plants can be taken outside if there is not enough space on the flowering shelf for all of them near harvesting.

A light tight curtain can be made from black vinyl, or other opaque material, with a reflective material on the other side to reflect light back to the plants. This curtain can be tied with cord when rolled up to work on the garden, and can be velcroed down in place to make sure no light leaks in or out. If the shelf is placed up high, it will not be very noticeable, and will fit in any room. Visitors will never notice it unless you point it out to them, since it is above eye level, and no light is being emitted from it.

Flowering plants like very high P level foods, such as 5-50-17, but 10-20-10 should be adequate. Nutrients should be provided with each watering when first flowering.

Trace elements are necessary too; try to find foods that include these, so you don not have to use a separate trace element food too. Home improvement centers sell trace element solutions rich in iron for lawn deficiencies, and these can be adapted for use in cultivating the herb. Prices for these mass produced fertilizers are significantly cheaper than the specialized hydroponic fertilizers sold in indoor gardening shops, and seem to work just fine.


1 tspn high P plant food, such as 15-30-15, or 5-50-17, etc.

1/2 tspn epsom salts

1 tspn Oxygen Plus Plant Food (Optional)

1 tspn Trace Element food

I cannot stress enough that during the FLOWERING PHASE, the dark period should not be violated by normal light. It delays flower development due to hormones in the plant that react to light. If you must work on the plants during this time, allow only as much light as a VERY pale moon can provide for less than 5 minutes. Keep pruning to a minimum during the entire FLOWERING PHASE.

A green light can be used to work on the garden during the dark period with no negative reactions from the plants. These are sold as nursery safety lights, but any green bulb should be OK. It is best to keep the dark hours a time when you would normally not wish to visit the garden. Personally, I like my garden lit from 7pm to 7am, since it allows me to visit the garden at night after work and in the morning before work, and all day long, while I am too busy to worry about it, it lies unlit and undisturbed, flowering away.

Flowering plants should not be sprayed often as this will promote mold and rot. Keep humidity levels down indoors when flowering, as this is the most delicate time for the plants in this regard.

Early flowering is noticed 1-2 weeks after turning back the lights to 12 hour days. Look for 2 white hairs emerging from a small bulbous area at every internode. This is the easiest way to verify females early on. You can not tell a male from a female by height, or bushiness.

3-6 weeks after turning back the lights, your plants will be covered with these white pistils emerging from every growtip on the plant. It will literally be covered with them. These are the mature flowers, as they continue to grow and cover the plant. Some plants will do this indefinately until the lights are turned back yet again. At the point you feel your ready to see the existing flowers become ripe ( you feel the plant has enought flowers), turn the lights back to 8-10 hours. Now the plant will start to ripen quickely, and should be ready to harvest in 2-3 weeks. The alternative, is to allow the plant to ripen with whatever natural day length is available outside, or keep the plants on a constant 12 hour regimen for the entire flowering process, which may increase yield, but takes longer.

Plants can be flowered in the final stages outdoors, even if the days are too long for normal flowering to occur. Once the plant has almost reached peak floral development, it is too far gone to revert quickly to vegatative growth, and final flowering will occur regardless. This will free up precious indoor space sooner, for the next batch of clones to be flowered.

Look for the white hairs to turn red, orange or brown, and the false seed pods ( you did pull the males, right?) to swell with resins. When most of the pistils have turned color (~80%), the flowers are ripe to harvest.

Don not touch those buds! Touch only the large fan leaves if you want to inspect the buds, as the THC will come off on your fingers and reduce the overall yield if mishandled.

6 comments to Marijuana Flowering Guide

  • kathy

    I have having a problem with my clones. They are about 1 1/2 feet tall or more. I have them with 14.25 LED and Sunlight hours. They have started to flower. Why? Kush strains and Sativa strains.

  • Washington Cannabis search

    Oh, your plant with the “little balls” and such, if from seed, is likely a male.
    If clone, it may be hemaphroditic

  • Washington Cannabis Research


    You keep saying, “in all my years,” so I would think you would be using a good grow bible. You must know your info well. You will notice things you may not have when you look something up for the third, fourth or 20th time.
    If your book is not well worn & marked, you haven’t really used “all of your years” for increasing your knowledge of a very exact (well close) process.
    Understand the seasons. Know what a Solstice and Equinox are. Know the difference. The first day of a season is either a Solstice (Sol is another word, in many languages & in this suffix, for sun). Equi, is just a suffix for equal). So, there are 4 days of the years that signify seasons-2 Solstices or “Sun Events” & 2 Equinoxes or “Equal (Sun) Events”
    So, 2 days of the year the Sun is in, or has an Equinox. The Sunlight is of equal lengths 12hrs. on & 12 hours off. On the first day of spring, as the days are growing longer, the day and night are of equal lengths 12 hours. 12/12. Then the days get longer and longer until you have the day with the most sunlight-the longest day! This is the first day of summer! This is a Solstice/A SUN EVENT. The sun shined for 15 hours the night was only 9 hours. So everything is warm and growing.
    Remember the sunlight!
    After the longest day, when the sun was out so very long, it begins to slowly shine less. Maybe only 2 or 3 minutes a day less, but everyday after the Summer Solstice or longest day, the days get shorter and shorter and on the first day of the next season-Autumn or Fall-is the 2nd Equinox. So the length of daylight is once again exactly the same as the length of the night. That would be 12 hours light/12 hrs. darkness.
    The difference in the Fall Equinox and the Spring is that in the Spring the days are getting longer for great growth. The Fall Equinox sees the days getting shorter & shorter until the first day of the 4th Season, Winter, when the daylight is the shortest. The sun shines the least the night is very long. This 4th and final season IS your 2nd “Sun Event.” Winter Solstice. The “Sol” was at its shortest.
    You must be mother nature, and you must mimic nature.

  • nancy

    My plants are flowering and there are swollen things that look like seed saks, but no seeds… ive been growing for years…. usually 3 plants is the norm…. this year on one plant i saw something I’ve never seen before… at the “V” on the stalks there are two long threads…. almist looks like fishing line. In all my years I’ve never seen this….. I’ve read somewhere thst they are “bud fibres”… I’ve never heard of this… good or bad? They dont seem to be affecting the plant in any way…. ive just never seen them… anyone know why?

  • Lisa

    My plant is in the flowering stage but the flowers seems small and I am having a hard time seeing even thru this cheap magnifying glass to see changes. Can I cover it too if I bring indoors to induce more flowering and cover it?

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