What you need to know at a glance:

  • Flowering time depends on the strain
  • Most strains will flower within 60 days or so
  • The range is 56 to 63 (8 to 9 weeks) but this depends on the strain
  • Landrace sativas from tropical areas are known to have very long flowering periods (exceeding ten weeks)

Growing Indoors versus Outdoors

When it comes to growing marijuana outdoors, you generally plant your seeds in May and then harvest in October. You can fluctuate this timeline a bit, planting earlier, harvesting earlier or later, according to the plant. But the general concept is that the changing of the seasons dictates the life cycle of the plant.

However, when growing marijuana indoors, there is no seasonal light cycle or changing of the seasons. The light cycle and “season” is controlled by the grower. Therefore, it is helpful to know how long the flowering stage lasts when growing indoors.

Marijuana Has Two Photoperiods: Vegetative and Flowering

Marijuana is a photoperiod plant, which means it has two distinct periods of growth. The first period is referred to as the “vegetative” period, followed by the “flowering” period, or “bloom” period.

The Vegetative Period is the first of the two stages

The Vegetative Period occurs in the summer, where the daylight exceeds the darkness of night. Therefore, when growing indoors, the grower must mimic this light cycle in order to keep the plant in a vegetative state and prevent flowering.

To maintain the vegetative state of the plant, the grower must keep the lights on for more than 15 hours per 24 hour period. However, you can exceed this amount as you wish. It is not uncommon for indoor cultivators to leave the lights on a full 24 hours.

Correctly utilizing the Vegetative Stage before flowering

The purpose of the Vegetative stage is to grow the plant to an appropriate size for it to flower. If you flower a seedlings (a tiny little plant only a couple weeks from sprouting), you will not have much bud, because the plant was so small.

Therefore, the vegetative stage is a time to grow your plant to the correct height and size for optimal flowering yield and quality. But there is another very important objective during the vegetative stage.

Use your time during the Vegetative period to top and train the plants

While you are vegging your plants, which is normally 5 to 8 weeks indoors depending on how big you want them, you should use this time wisely. And the best use of the time spent in veg is to top your plants, at least once but twice is better, and to train them.

By topping your plants, you set them up for a better growth pattern during the flowering stage. You also guarantee a higher yield, since you now have more tops that can become colas.

Lastly, you create a better shape to the plant that can be used in the trellis netting during the flowering period. So use your time wisely while the plant is in the vegetative phase and you will reap better rewards during the flowering stage.

Indoor Flowering time for marijuana plants

Now that you have vegged your plant to the appropriate size, topped your plant, and begun training it, you are now ready to flower the plant.

Setting up your grow for the 12/12 flowering light cycle

We cannot stress enough the importance of using trellis during the flowering stage. This will improve your yields, and also quality by bringing more buds to the canopy surface so they are exposed to greater light density. The greater the light density, the greater the bud density.

So before you flip your light cycle to 12/12, set up your trellis netting and be prepared to start using it during the post-veg stretch that occurs in the first three weeks.

The flowering time depends on the strain  

Each and every strain has its own flowering time, but most of the popular strains these days will finish flowering in about 60 days. Most marijuana growers prefer strains that are in the 8-week to 9-week ranger, and most breeders try to accommodate this preference.

For cultivators that run commercial operations on a perpetual basis, the obvious choice are 8-week and 9-week strains. Strains that fit that time frame are perfect for setting up recurring flower cycles and harvest cycles. Once the flowering time begins to exceed nine weeks or 60 days, you get less harvests per year and it really impacts the business side of things.

Some cannabis strains have unusually long flowering periods

There are some strains that have very long flowering periods. For example, many tropical landrace sativa strains are known to have very long flowering periods, up to 15 weeks or so. This would make sense, given that in a tropical climate, there are not as many seasons. Usually a “wet” season and “dry” season. And the weather remains pretty similar all year round.

When you are shopping for seeds from your preferred cannabis seed bank, look for information on the flowering times so you are not surprised. The breeder usually provides this information on the packaging for the seeds.

Knowing when is the right time to harvest your flowering marijuana plants

If you have chosen a strain that is considered an “8-week” strain or a “9-week” strain, then here are some basic parameters for you to follow.

An 8-week strain will conclude on Day 56. But if you harvest a day or two early, or a day or two late, you will probably be okay.

A 9-week strain will conclude on day 63, but again, you can be a little early or late and not cause too much damage.

If you harvested either strain on Day 60, you will probably be alright and not notice too much difference, depending on your level of expertise. Again, it depends on what you are trying to accomplish. If you are seeking to win a cannabis cup, the fine details matter.

But if you are just trying to get some practice runs in, there is no better way to practice than by doing. And by growing and harvesting through multiple cycles, you will learn how to best cultivate your favorite strains.

We firmly believe that practice makes perfect, and that nobody gets it right the first couple of runs. Even professional cultivators with years of experience can stumble when they move to a new facility, or construct a new grow room. Different environments and different ecosystems all affect the plant. So get some runs under your belt, knowing that you will get better and better with each cycle.

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