You also have to remember that your plants will approximately double in size from the beginning of the flowering stage to the end. This means you want to take them out of vegging when they are about half of the final desired size.
Starting with clones obviously saves a bit of time over starting with seeds.
Why would you want this period to last any longer than it has to, though?
Read Why Does My Weed Smell Like Hay? for more on what can happen if you dry your buds too quickly. I’m sure you can already guess one issue from the title of that article.
If speed is the only thing that matters, you could switch to a 12/12 light cycle and begin flowering as soon as possible. Of course, this will result in much smaller plants and correspondingly smaller yields. We definitely do not recommend this, unless it is your goal to have small plants.
The reason this stage can last indefinitely when growing indoors is that you are the one who provides the signal for your plants that it is time to start flowering.
The primary factor that influences how long it takes cannabis to grow is the strain. Choosing a fast-growing strain can shorten the time considerably.
Marijuana light cycle: indoor—16 hours a day; outdoor—at least 6 hours of direct sunlight (“full sun”), plus several hours indirect sunlight
Seedling stage length: 2-3 weeks
Harvest happens sometime between September and November. This depends on your local climate, as well as the weather that particular year—one year it could be the end of September, the next, end of October, and growers in the Pacific Northwest will have to pull down their crops earlier than those in Northern California.
The growth stages of marijuana can be broken down into four primary stages from seed to harvest:
Marijuana light cycle: 12 hours a day
When your marijuana plant becomes a seedling, you’ll notice it developing more of the traditional cannabis fan leaves. As a sprout, the seed will initially produce leaves with only one ridged blade. Once new growth develops, the leaves will develop more blades (3, 5, 7, etc.). A mature cannabis plant will have between 5 or 7 blades per leaf, but some plants may have more.
What are a weed plant’s growth stages?
Buds typically grow the most toward the end of the flowering life cycle. You probably won’t notice much budding out at the beginning of the flowering stage, and it will slow down toward the end of the cycle, when buds become fully formed.
If you’re growing indoors, you can force a weed plant to flower after only a few weeks when it’s small, or after several weeks when it’s big. If you’re growing outdoors, you’re at the whim of the seasons and will have to wait until the sun starts to go down in fall for it to flower and then to harvest.
You can control the timing if you plan ahead.
These factors have the greatest impact on total time from seed to harvest:
Auto-flowering plants tend to stay small since they go from seed to harvest in under 3 months. These auto-flowering plants produced about 7 ounces.