Cannabis plants go through a series of stages as they grow and mature, and those different growth stages call for different amounts of light, nutrients, and water.
It’s important to know these stages and how long each lasts to know what the plant needs and when. Knowing where your cannabis plants are in their life cycles will dictate when to prune, train, and trellis your plants, and when to harvest.
How long does it take to grow a marijuana plant?
Generally speaking, it takes anywhere from 10-32 weeks, or about 3-8 months, to grow a weed plant from seed to harvest. 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.
When growing outdoors, you’re at the whim of the seasons and will have to wait until the sun starts to go down in the fall for plants to flower, and then to harvest.
However, one way outdoor growers can control the flowering cycle is by using light deprivation techniques.
What are a weed plant’s growth stages?
The growth stages of marijuana can be broken down into four primary stages from seed to harvest:
- Germination (3-10 days)
- Seedling (2-3 weeks)
- Vegetative (3-16 weeks)
- Flowering (8-11 weeks)
Cannabis seed germination
Seed germination length: 3-10 days
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
The first marijuana plant stage begins with the seed. A cannabis seed should feel hard and dry, and be light- to dark-brown in color. An undeveloped seed is generally squishy and green or white in color and likely won’t germinate.
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Once your seed has germinated, or sprouted, it’s ready to be placed in a growing medium, like soil. The tap root will drive down while the stem of the seedling will grow upward.
Two rounded cotyledon leaves will grow out from the stem as the plant unfolds from the protective casing of the seed. These initial leaves are responsible for taking in sunlight so the plant can grow healthy and stable.
As roots develop, the stalk will rise and you’ll begin to see the first iconic fan leaves grow, at which point your cannabis plant can be considered a seedling.
Can you speed up the germination process?
No. Cannabis seeds are delicate and don’t like to be moved around. They need a warm environment that doesn’t fluctuate in temperature, and not too much water. Once you put them in soil, we recommend leaving them be.
Quality seeds typically have high germination rates, but you may get some duds that don’t sprout. Let them do their thing; helping them along can decrease their chance of survival.
Seedling stage in cannabis plants
Seedling stage length: 2-3 weeks
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
When your marijuana plant becomes a seedling, you’ll notice it developing 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, or “fingers” (3, 5, 7, etc.). A mature cannabis plant will have between 5 or 7 blades per leaf, but some plants may have more.
Cannabis plants are considered seedlings until they begin to develop leaves with the full number of blades on new fan leaves. A healthy seedling should be a vibrant green color.
Be careful to not overwater the plant in its seedling stage—its roots are so small, it doesn’t need much water to thrive.
At this stage, the plant is vulnerable to disease and mold. Keep its environment clean and monitor excess moisture. Be sure to give it plenty of light.
Even if growing outdoors, a lot of growers will start their seeds inside under an artificial light to help them through this delicate stage of marijuana growth.
If you buy a clone from a grower or breeder it will be a seedling, so you can skip the seed germination phase.
Vegetative stage in cannabis plants
Vegetative stage length: 3-16 weeks
Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors
The vegetative stage of cannabis is where the plant’s growth truly takes off, and it typically lasts 3-16 weeks. At this point, you’ve transplanted your plant into a larger pot and the roots and foliage are developing rapidly. This is also the time to begin topping or training your plants.
Be mindful to increase your watering as the plant develops. When it’s young, your plant will need water close to the stalk, but as it grows the roots will also grow outward, so start watering further away from the stalk in the soil so roots can stretch out and absorb water more efficiently.
Vegetative plants appreciate healthy soil with nutrients. Feed them with a high level of nitrogen at this stage.
Cannabis plant flowering stage
Flowering stage length: 8-11 weeks
Marijuana light cycle: 12 hours a day indoors; full, direct sun 6 hours a day outdoors
The flowering stage is the final stage of growth for a cannabis plant. This is when plants start to develop resinous buds and your hard work will be realized. Most strains flower in 8-9 weeks, but some can take even longer, especially some sativas.
Outdoors, flowering occurs naturally when the plant receives less light each day as summer turns into fall.
Indoor growers can trigger the flowering cycle by reducing the amount of light marijuana plants receive from 18 to 12 hours a day.
There are three subphases of the flowering stage:
- Flower initiation (week 1-3): The plant will continue to grow and females will develop pre-flowers—pistils, or white hairs, will grow out, which are the beginnings of buds.
- Mid-flowering (week 4-5): The plant itself will stop growing and buds will start fattening up.
- Late flowering/ripening (week 6 and on): Trichome density will increase and plants will get very sticky; keep an eye on the color of the pistils to tell when to harvest.
There are a number of changes to consider once plants go from the vegetative stage to the flowering stage:
- Don’t prune when plants are flowering, as it can upset their hormones
- Plants should be trellised or scrogged so buds will be supported as they develop and air can flow through plants
- Consider giving plants bloom or phosphorus nutrients
What does the pre-flower stage look like?
Pre-flowers are the beginnings of cannabis plant sex organs. If you’re growing regular seeds, you’ll likely have a mix of male and female plants and will need to determine the sex of your plants to discard the males. It’s imperative to separate males so they don’t pollinate the females.
Pre-flowers appear at the nodes of the plant, where a branch grows out of the main stalk. Females will develop an oval-shaped bract with hairs or pistils sticking out, while males will develop round pollen sacs.
Learn more about pre-flowers and cannabis plant sexing in our anatomy article.
How to tell when a cannabis plant is ready to bloom
When growing outdoors, weed plants will start flowering, or blooming, after the summer solstice, when the daily amount of light starts to decrease. Plants will start developing pre-flowers, as mentioned above, telling you that flowering has initiated.
When growing indoors, growers make the decision to force blooming or “flip” plants into flower by cutting off the amount of artificial light they receive.
What to do when cannabis plants flower early or late
The amount of time it takes a plant to finish, or be done flowering and ready for harvest, will depend on what strain it is. Typically, indicas finish flowering early and sativas finish flowering late.
Note information from the breeder when you buy seeds to grow to get a sense of how long it takes to flower. You may have to harvest some plants early and some late depending on their finish times.
For late-flowering strains, keep an eye on the weather and make sure cold weather doesn’t ruin your plants before they finish.
When do buds grow the most?
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.
Once buds have reached full maturation, it’s time to harvest your marijuana. How long it takes to harvest buds depends on many factors, including harvesting methods and how many plants you harvest.
How long can a marijuana plant live?
Weed plants are annuals, meaning they grow and live for one season and then die. Wild cannabis plants grow seeds and drop them when they die, which will grow into new plants the following year.
When harvesting, plants are cut down and die in order to get their buds. New seeds need to be planted in order to grow more plants.
If left unharvested, weed plants will eventually wither and rot within a few months after the peak flowering phase.
When should you grow marijuana?
If you’re growing outdoors in the Northern Hemisphere, growers usually get their seeds between February and April and start germinating seeds by the end of April.
Many start growing seedlings inside in a more controlled environment because seedlings are more delicate, and then put the seedlings in the ground outside once they’re a little bigger and the weather is warmer.
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.
Harvesting 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; growers in the Pacific Northwest will have to pull down their crops earlier than those in Northern California because of cold weather.
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.
Important dates for growing marijuana outdoors
Many growers begin germinating seeds as early as February and March in order to have big plants come harvest time, but the Spring Equinox is a good reminder that it’s time to kick off the outdoor growing process and start germinating your seeds if you haven’t already.
Many farmers wait until after Mother’s Day in May to put their plants outside. Just make sure all of your plants are outside by the Summer Solstice at the latest.
The weather will start to turn and the sun will begin descending in the sky as your plants fatten up with sweet, sticky buds. It might be tempting, but the Fall Equinox is about when to start harvesting. It’ll depends on your climate and the year—it could happen a little before or after.
Everything should be cleaned up, dried, and curing by Thanksgiving, and in some places, even by Halloween.
As winter approaches, it’s prime time to make your own cannabutter, topicals, or tinctures with all that trim from the harvest. Kick your feet up, relax, and hunker down for the cold, it’s been a long growing season!
Notes on marijuana growth phases
We can’t stress enough that the timeframes in the above graphic are ranges of time for the Northern Hemisphere. You’ll need to adjust them based on your specific region and local weather and climate.
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 next year.
Take meticulous notes on when and how you perform each step, noting:
- Weather
- How much water you give plants, and at what intervals
- Nutrient amounts
- When you top and prune
Pictures will also give you a better sense of how your plants look along the way.
Learn more about harvesting weed
Pat Goggins and Trevor Hennings contributed to this article.
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