Are Your Cannabis Plants Not Flowering? Here’s What You Can Do To Fix It!

Are you having trouble getting your plants to flower? There are a few easy-to-fix mistakes that could be preventing you from seeing a harvest.

Cannabis plants do not start making sex-specific parts like buds until they reach the “flowering stage” of life. If your cannabis plant is growing without making buds, it means that it’s still in the “vegetative” stage of life, or the cannabis plant isn’t female.

  • Vegetative Stage – “Child” stage – plant grows just stems and leaves with no buds
  • Flowering Stage – “Adult” stage – plants starts growing sex-specific features like buds or pollen sacs.

Whether growing indoors or outdoors, the stage of your cannabis plant is usually determined by light schedules.

So before cannnabis plants start flowering, they are in the vegetative stage which means the plants only grow leaves and stems, with no buds.

A grower can tell when the vegetative stage has ended because the plant starts growing gender-specific parts in addition to leaves and vegetative growth.

In the second stage of life, the flowering stage, female cannabis plants will start to make buds (flowers). Male cannabis plants will only make pollen sacs (no buds) and are usually discarded by growers. 


Dumb question, right? But, if you have a male and don’t know it, it will never produce buds, no matter what you do.

You can easily identify a male cannabis plant once it starts to show its gender. Look at the nodes where the leaves and side branches emerge from the main stem. Females develop tiny pre-flowers and males develop pollen sacks. They’re hard to tell apart when they first show, but within a day or two, the pre-flowers shoot out two tiny hair-like stigmas. The pollen sacks will continue to multiply until they look like miniature clusters of green grapes.

Wait a minute. I bought feminized seeds!?! Such seeds are bred using feminization techniques. This process is very reliable, and seeds turn into female plants 99.9% of the time. If you get a male plant from a pack of feminized seeds, you’ve either hit the bad luck lottery and fell into that 0,1% category, or there was an error at packaging stage, and regular seeds got mixed up with feminized beans. Mistakes happen, so do yourself a favour and watch for signs of sex no matter what you buy.


Cannabis is like any other plant. It needs spectrum energy to grow. When planted outdoors, cannabis follows a seasonal cycle in spring and summer. Flowering generally occurs in late summer. It is also triggered by the summer solstice (June 21st). After this date, days begin to shorten gradually. Longer nights are thought to trigger blooming. Blooming usually starts in early August.

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If you are growing indoors, obviously the lighting cycle is man-made. If you are not successful in getting your plant to bloom, the first culprit is probably the light. You will need to tweak your setup to make sure that it gets the right kind and temperature of light for the right amount of time.

A marijuana plant growing outdoors will do just fine in lots of sunlight and begins flowing in the fall. But when it comes to big, compact indica buds, the plants grown indoors require about 40 watts of HPS or MH light per square foot. However, sativa buds require around 60 watts. In the first stages of growth, you can use both the HPS and MH lamps. You will need to change the light schedule for indoor growing to get your plants to start flowering.


Using the right lights is vital for getting your plants to flower. But, the time spent in the dark is another factor that you can’t overlook. During the vegetative state, many indoor growers choose to leave their lights on 24 hours a day. If the plants begin to show signs of stress during the veg phase, you can bump them down to 18 hours under the light and 6 hours of complete darkness.

Once your plant gets to a healthy, durable size you can force it to flower by putting it under a strict 12/12 light cycle. That’s 12 hours beneath the red light and 12 hours in complete darkness. The 12/12 cycle is meant to mimic summer nights after they begin to get longer post-solstice.

Any light leaks or interruptions that happen during the 12/12 phase can stop your plant from flowering and send it back into vegetative growth. Some experts even suggest that something as simple as shining a flashlight on your plant during its artificial nighttime can force it back into veg. You might want to consider investing in an automatic light timer to make it easier stick to a strict light schedule.

You might want to consider investing in an automatic light timer to make it easier stick to a strict light schedule.


Do your plants contain autoflowering genetics? Are you trying to get them to bloom under 24 hours of light? If so, try cutting the light back to an 18 hours on, 6 hours off schedule. Old-school autos, with a high percentage of ruderalis, bloom like crazy starting at the third week after germination, even when the lights are on around the clock. However, breeders have been answering demand for stronger, higher yielding automatics by decreasing the amount of ruderalis in newer automatics. It’s simple math and science. Increase the ruderalis, and darkness requirements go down along with THC and yield. Decrease it, and the opposite happens.

If you’re growing photoperiod plants in the same environment as your autos, don’t worry about reducing light from 24 hours to 18. It won’t hurt the plants one bit and it might do them some good. If you still don’t see pistils starting to form after two weeks of 18/6 lighting, maybe your plants are actually photoperiod instead of autoflowering. Again, mistakes happen.


Photoperiod cannabis plants will not flower, no matter how big or how old they get, unless they receive at least 12 consistent hours of uninterrupted darkness in each 24-hour period. Professional growers leverage those rules of nature to maintain their best mothers in a vegetative state for years so they can make clones. Most plants will start to form buds somewhere between 10 days and 3 weeks into a 12/12 lighting schedule, and here’s why.

When the lights are on, photoperiod cannabis plants produce phytochrome red and phytochrome far-red in about equal amounts. When the lights are out, phytochrome far-red changes into plain old red. When red outnumbers far-red by the right amount, the plant will start blooming. To jumpstart this process, some growers turn the lights all the way off and drown their plants in complete darkness for 36 hours before they set their timers to 12/12.

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