Generally speaking, it takes anywhere from 10-32 weeks, or about 3-8 months, to grow a weed plant from seed. It’ll be quicker if you start with a clone or an autoflower seed.
The biggest variability in how long a marijuana plant takes to grow will happen in the vegetative stage—after the seedling phase and before flowering.
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.
When should you grow marijuana?
If you’re growing outdoors in the Northern Hemisphere, growers usually get their seeds between February and April, and you should start your seeds by the end of April. Some growers will start their seedlings inside in a more controlled environment because seedlings are more delicate, and then put their seeds in the ground outside once they’re a little bigger. If you’re growing clones or autoflowers, you have a grace period of another month or so. Plants usually need to be outside, in the ground, by the end of June.
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.
If you’re growing weed indoors, you can grow whenever you like. Keep in mind that the outside environment will affect your grow space—you may need to add heaters in the winter or fans and ACs in the summer. Other than that, you can start seeds whenever you like and flip them into flower whenever you like, depending on how big you want the plants.
Notes on marijuana growth phases
Be sure to keep a grow journal to track the progress of your plants. Looking back on your notes will help you learn from mistakes and maximize the quality and quantity of your buds.
Take meticulous notes on when and how you perform each step, as well as what the weather is like. Other notes can include how much water you give plants, at what intervals, and how much nutrients you give them. Pictures will also give you a better sense of how your plants look along the way.
Step 1: Getting your weed growing equipment = 1 day to 2 weeks
If you know what you are looking for then this could happen quickly. We will help you with this later on as we set up the grow-rooms and do some grows with different styles and grow mediums.
Step 2: Getting your clones or seeds = 1 day to 4 weeks
Getting clones (cuttings from healthy mother plants) is easy to do in areas that allow cannabis cultivation. But in states or countries where it is illegal to grow, obtaining healthy clones can be a challenge. Seeds, on the other hand, can be ordered on the internet and generally take 2 to 4 weeks before they arrive by mail.
Step 3: Germinate The Seeds = 12 hours to 8 days
If starting with clones this can be skipped. The average time to germinate is 2 or 3 days. Make sure to check your seeds every day because seedlings can sprout in as little as one day. You’ll know your seed has germinated when your seed has popped and displays a tap root formation.
Step 4: Seedling Phase = 1 week to 4 weeks
Once again, can be avoided if using clones and not seeds. As your cotyledons begin to take shape, so will your cannabis leaves in a single leaflet form. Generally, growers can give their seedling a light amount of nutrients after the third set of leaves begins to appear.
Step 5: Vegetative Phase = 2 weeks to 6 Months!
Yes, that is correct. This stage in the plants life has a huge fluctuation in how long it needs to take. You, as the grower, hold all the power and get to choose how long this phase is. Once you change the light cycle that the plant receives to 12 hours of light, and 12 hours of darkness per day, the plants will switch to the next phase, which is flowering.
If you want to, you can switch the lights to 12/12 right away and force your plants to flower! The sooner you change to 12/12, the faster your plants will flower, and the sooner you can move on to the next crop. But, keep in mind, the less amount of time you keep your plants in the vegetative phase, meaning getting at least 18 hours of light per day, the smaller your plants will be, and the less marijuana you will have to use. If you are concerned with how big your plants will grow, maybe because you only have a small space to grow in, you can grow cannabis that only grows only a few inches tall, and you could even grow it the entire time in a little plastic cup if you wanted to!
Keep in mind that buds do not form for at least 2 to 3 weeks in the vegetative phase when beginning with seeds. Most growers allow their plants to stay in the vegetative stage from a few weeks to a few months so they get big enough and will end up with a sizable harvest. Bigger plants produce more buds! But, many growers choose instead to grow small plants and to harvest more often with smaller yields each time. We recommend at least 3 weeks or more in the vegetative stage with at least 18+ hours of light each day for optimal yields. Even 24 hours of light per day is sometimes better, with certain strains.
The more light, the more buds!
Keep in mind that cannabis plants usually double in size from vegetative phase to when they are done flowering. This means is sometimes best to change to 12 hours of light and 12 hours of darkness once the plants are one-half the size that you feel your grow room has adequate space for.
During the vegetative phase, you can use a number of cultivation training techniques such as super cropping, crimping, topping, tying, bending, sea of green (SOG), screen of green (SCROG), and trellising to alter the growth, direction, height, and quality of your crop.
Autoflowering strains, however, have a different vegetative time period than regular feminized seedlings. Autoflowering strains will have at least two to three weeks of vegetative growth before they automatically start showing any bud formations regardless of photoperiod.
Step 6: Flowering Phase = 6 weeks to 3 months
In nature, cannabis plants start to flower in the fall months, when they are receiving less light. The decrease in light signifies to the plants they are nearing the end of their life cycle and its time to begin flowering.
Indoors, this action is done by changing the amount of light the plants receive to a schedule of 12 hours of light, and 12 hours of uninterrupted darkness. The plants will require less nitrogen during this time than they have had in the previous vegetative phase. The needs for phosphorus and potassium will increase, so you will now use a nutrient with a higher P&K ratio. If at this time you still are not sure if the plants have revealed the sex or not, they will in about 7 to 10 days after being in the 12/12 light cycle. Look for two white hairs coming out of the nodes on the plants. These hairs are the pistils that are found on the females.
Most cannabis plants flower for around 8-14 weeks. Depending on the strain, some may flower a lot longer than others. Pure indica strains usually finish around 8 weeks of flowering, while pure Sativa strains usually finish around 12-14 weeks. Some Sativa strains have been known to flower for 16 weeks or longer. For this reason, indica strains are most commonly the kind that is grown indoors.
Most growers like to grow, harvest, sell, and get back at it as quickly as possible to turn a faster profit. If you are not in it for the profit, sativa strains can be fun to grow. You could let them grow real big and tall if you have the ceiling space or outdoor area for them. Make sure to research the strain your growing so you have a general idea of the flowering time.
Autoflowering strains can have a short flowering stage and begin to flower after just three weeks. Autoflowering strains can be ready to harvest 5 weeks after. That means that you can grow an autoflowering seed in just eight weeks.
Keep a close eye on any new sex organ formations to determine the sex of your plants within the first two weeks of flowering. You will be able to tell whether your male plant needs to be carefully extracted from the grow site or whether you have a female on your hands. It’s important to separate the males from the females to prevent the pollination of females.
Pruning too early into the flowering stage can affect the hormones of the plant and the number of buds produced.
Ultimately the flowering phase will depend on the genetics of your strain.
Fast-flowering strains can grow in a period of between six to eight weeks. Fast-flowering strains include:
Girl Scout Cookies (GSC)
Original Glue (Gorilla Glue #4/GG4)
Granddaddy Purple (GDP)
A medium flowering growth rate can take between eight to 12 weeks. Most strains will have a medium flowering time. Medium-flowering strains include:
Long flowering times between 12 and 14 weeks occur in most sativa, landrace, and Haze strains. Long-flowering strains include:
San Fernando Valley OG
Step 7: Harvesting = 1 to 3 days
Harvesting times can vary depending on your strain’s height, yield, and overall quality, as well as your experience with drying, curing, and trimming. Quality cannabis buds can dry in about four days but usually take a week or more for a slow and full drying process. Your bud should be dry enough to avoid mold, but not too dry.
Curing can take anywhere from a couple of weeks to a little over a month. Some users may leave their cannabis curing for up to two months or even six months for some strains. Curing is another long and slow process intended to maximize the effects of your bud, especially for medical users.
Trimming times can depend on your experience. Of course, hand trimming will be more time-consuming than using a commercial and automatic trimming machine, but hand-trimming produces more carefully manicured flower compared to the one-size-fits-all appearance of a machine trimmed crop.
Generally, a single person can trim about a half a pound in about 8 hours. That means that you need two full shifts, so to speak, to completely trim a pound of weed. A quarter of a pound can take about 3 hours. For slower trimmers, one ounce per hour is the average. Using a household trimming machine can cut down you are trimming time in about half.
And that’s it! All you need to do is cure and trim and you’re cannabis is ready for use!