In your quest to find the answer to the question ‘how long does it take to grow weed ‘, you have probably come across numerous sources with contradictory answers. Well, that’s because marijuana is a diverse plant with varying genetics. Most of the answers are based on one type of species or strain. Well, now you don’t have to look anymore because this article will answer the question comprehensively and take you step-by-step through the stages of marijuana growth. It will cover everything you need to know about the four stages of growth and the factors that may prolong or shorten each phase. So, how long does it take to grow a marijuana plant?
The answer will depend on two factors: the genetics of your cannabis seeds and whether you decide to grow indoors or outdoors. Are you going for Sativa, Indica, or Hybrid seeds? Are you cultivating photoperiodic plants or autoflowers? Do you prefer to cultivate your plants in an open or controlled environment? These factors play a significant role in deciding whether you will grow cannabis for 9 weeks or up to 32 weeks. Below is a breakdown of the weeks a cannabis plant takes in each stage of its growth.
Autoflowers grow very fast and take between 8-12 weeks from seed to harvest-ready. When growing your cannabis plants outdoors, one has little to no control of the environment. It takes an average of 6 months for the plants to mature.
The stages of marijuana growth
Different cannabis grow stages and the optimum conditions required for healthy plants.
Germination stage (2-10 days)
The first step towards achieving healthy plants and bountiful yields is selecting viable seeds. Buy your seeds from a reputable seed bank to guarantee a 90+% germination rate. The seeds should be small, dry, hard, and brown with stripes.
Under optimum conditions, the seeds germinate within 2 to 10 days, depending on how hard the shell is. For a seed to germinate, it needs water (moisture), warmth, darkness, humidity, and peace. Yes, it would be best not to disturb the seed by touching it or moving it while germinating. Giving it the peace it requires is essential to growing a healthy plant.
Additionally, do not hurry up the process by forcing the shell off or using sandpaper. Provide the necessary conditions for germination and let nature take its course. In rare cases where it may be difficult to germinate seeds, this can sometimes occur if a seed has a thicker shell, as a last resort you can lightly scarify the seed to assist and speed up the germination process.
Different methods used to germinate cannabis seeds.
You can germinate your seeds in either of the following ways:
Paper towel technique: soak two paper towels in water. They should be wet but not dripping. Place them on a plate, and then put your seeds on top of them. Take two more paper towels, soak them in water, place them on top of the seeds, and cover them with another place. Store in a dark, warm place. Check the progress every 24 hours and resoak the paper towel if they appear dry.
Direct planting: you can decide to germinate your seed on the soil it will grow in. To do this, dig half an inch or one inch into the soil, place the seeds in the holes, and cover. Spray the soil with water and wait for the seeds to germinate.
Starter cubes and seedling plugs: these make the whole process much more manageable. All you need to do is place the seeds in the cube, add water, provide optimum conditions, and wait for germination.
Soaking the seeds overnight: place the seeds inside a container with lukewarm water for 24 hours. Remove the seeds and put them in a moist paper towel or the selected growing medium while providing warmth and darkness. Soaking triggers the hormones and cells to start the germination process.
The germination phase is the first hurdle of the stages of marijuana growth, usually this can easily be overcome by growing with good quality cannabis seeds. Have a read of our germination guide for more detailed instructions of the above listed methods.
When is the germination process complete?
The germination process may take even one day, while older seeds may take up to 2 weeks. The germination process is done when the taproot and the plant’s first oval-shaped cotyledon leaves appear (see the image below). The plant is officially in its seedling stage and ready for transplanting to a pot.
Transplanting your marijuana seedling
If you used the paper towel, glass of water starter cubes, or soaked the seeds overnight, you need to transplant your seedlings to their selected growth medium, whether soil, coco fiber, or DWC/NFT hydroponic system.
Autoflowers have a limited growth period, and as a result, many growers prefer to transplant the seedling into their final growth medium. This is opposed to transplanting it several times as they transition from one growth stage to the next. Autos do not have the time to recover and adapt if they are transplanted constantly, so this is recommended.
The marijuana seedling stage (2-3 weeks)
This is the phase where you need to focus on maximizing root development for healthy, high-yielding plants. Ensure the growth medium provides enough space for the roots to stretch downwards and horizontally. Use the right amount of water to avoid water clogging your plant, which ultimately leads to stunted growth, unhealthy plants, and unimpressive yields. Use a small grow pot with adequate aeration and drainage.
During the marijuana seedling stage, the plants grow new, large, serrated leaves that emerge from the apex (see image below). The leaves will take on a vibrant green hue and have blades/fingers (usually 3, 5, or 7). If growing with soil, avoid using nutrients as the medium contains enough food to sustain the plants for 2-3 weeks before transitioning into the vegetative stage. If growing in coco fiber or hydroponics, you can feed your plants with nutrients after they have developed 3-4 sets of true leaves. They would have already used up most of their energy at this point.
Place the lights as instructed by the manufacturer and observe the plants’ progress to make adjustments. Placing the light too close will cause heat burn, and placing it too far will result in elongated stems and a weak plant. The ideal lights for the seedling stage should have a PPFD level of 200 to 400. Utilizing T5 fluorescent bulbs is recommended as they tend to be gentle on delicate plants.
Maintain a light schedule of 18/6 (recommended) to allow the plants to make enough energy to facilitate their growth in the coming weeks. The temperature and humidity should be between 22°C to 27°C and 65% to 80%, respectively. Check your grow medium to ensure that the PH ranges between 6-6.8 for soil, 5.2-6.8 for coco fiber, and 5.5-6.5 for hydroponics. When the plant starts to grow new digitate leaves with 5 or more blades/fingers, it is a sign of transitioning into the vegetative stage.
During this stage be very careful with the plants, marijuana seedlings are incredibly delicate and any slight stress can kill the plant at this stage. Use extreme care when watering seedlings and make sure the light is not too hot. Ideally use a mist sprayer to water them, this will prevent any damage to the stem from the weight of the water.
Marijuana Vegetative Stage (3 – 15 weeks)
The vegetative stage is where the plant focuses on growing vertically and horizontally. The plants experience a growth spurt in the leaves, stems, roots, and branches. This is their way of preparing for the budding stage, where they will have to be strong enough to manage the weight of the big flowers/buds. Ensure the grow pots are big enough to accommodate the plants’ growing needs.
At this stage, the plants require a lot of nutrients, so make sure you feed them accordingly. Use nutrients with high nitrogen levels and low phosphorus and potassium. Subject them to the standard 18/6 light schedule or try the 16/8 or the 20/4 schedule as per your needs and expectations. Give the plant enough time to rest after many hours of making food for its exponential growth.
This stage usually lasts between 3-15 weeks as different growers require varying lengths of time to maximize final yields. For example, cultivators who incorporate the ScrOG technique can have their marijuana plants in this stage for up to 15 weeks. Growers who utilize the SOG method may prefer instigating the transition immediately when the plant enters the vegetative stage rather than spending a few weeks growing bigger. Most cultivators grow their weed in the vegetative stage for 4-8 weeks on average.
Ensure that the growing space has adequate airflow and that the lights are kept within the recommended distance from the plant. In the vegetative stage, cannabis plants thrive when exposed to a light intensity of 400 to 600 PPFD and 40% to 60% humidity levels. Maintain temperatures between 22°C to 26°C (71°F to 79°F).
Within the 4th or 5th week into the vegetative phase, you may notice pre-flowering on the plant’s nodes. If you had bought regular, non-feminized seeds, this is the time to tell the male from the females. Only female plants are capable of producing buds/flowers. Consequently, if you grow cannabis for breeding purposes, you may keep both the male and female plants. However, if your sole purpose is to make flowers, this is the time to pluck the male plants as they may end up affecting your yield by pollinating the females.
Autoflowers remain in the vegetative stage for 2-4 weeks before automatically transitioning to the flowering stage. For photoperiod plants, changing the light schedule triggers the transition.
Final phase: The flowering stage (7-14 weeks)
The last and final stages of growing cannabis, the flowering stage. At this point the plant’s energy is centered on making flowers for a bountiful harvest. For indoor grown photoperiod plants, the transition happens when you alter the light schedules to 12/12. Plants grown outdoors will transition into the flowering stage as the days are shortened when autumn approaches. The plants automatically detect the shortened day in equatorial regions and begin the transition.
Depending on the type of cannabis species, the flowering stage may last between 7 to 14 weeks. Indicas take the shortest time, 8-10 weeks. Sativa cultivators will require patience as the plants can take between 10 to 12 weeks in the flowering stage. It can go either way for hybrids as some may flower for a record 6 weeks while others last for 12+ weeks.
The flowering phase is divided into 3:
Early boom week 1-3: The plant does its final stretching as bud sites start forming. Sativas grow up to 3 times the size they started in the flowering stage.
Mid boom week 4-5: the buds increase in size while the pistils grow in numbers. The plant stops growing and focuses on flowering. You can notice the dense flowers as they become fatter. The pistils start to darken.
Late boom week 6-8: pistils will appear orange, begin to curl inwards, and are engulfed by a layer of trichomes. The buds become dense and heavy.
Week 8+: The plants are ready for harvesting.
During the flowering stage, the plants have a heightened appetite for nutrients. Ensure you feed them as required to avoid under or over-feeding them. While making buds, the plants will require less nitrogen and more phosphorus and potassium.
The lights should have PPFD levels of 600-900. You can increase the intensity to go beyond the 1000 mark, but ensure you supplement with carbon dioxide to take your yields to the next level. The temperature should range between 18°C and 26°C (64°F to 79°F).
Cannabis plants in the flowering stage will need less humidity, so keep the reading steady between 40% and 50%. Keep the light schedule at 12/12 as altering this could confuse the plant into going back to the vegetative stage or lead to hermie plants.
Now that you understand how long it takes weed to grow, you should also learn to understand when your plants are ready for harvest.
Below is a list of the top factors determining when it’s suitable to harvest cannabis plants.
- The trichomes change color from clear to amber, white, or milky.
- Orange-red pistils that curl inwards
- Wilted, withered leaves
- Swollen calyxes
- Your preference: do you want to harvest early, mid, or late?
- Environmental conditions such as heavy rains and extremely high or low temperatures
- Type of strain you are growing and how long they take to mature.
Below is a summary of marijuana plant stages of growth and optimum conditions of each phase as highlighted in this piece.
|Factor||Seedling stage||Vegetative stage||Flowering stage|
|PH||6-6.8 for soil, 5.2-6.8 for coco fiber, and 5.5-6.5 for hydroponics||6-6.8 for soil, 5.2-6.8 for coco fiber, and 5.5-6.5 for hydroponics||6-6.8 for soil, 5.2-6.8 for coco fiber, and 5.5-6.5 for hydroponics|
|LIGHT INTENSITY||PPDF levels of 300 to 400||PPDF levels of 400 to 600||PPDF levels of 600 to 900. If more than 1000, supplement with CO2|
|TEMPERATURE||22°C to 27°C (71°F to 80°F)||22°C to 26°C (71°F to 79°F)||18°C and 26°C (64°F to 79°F)|
|HUMIDITY||65% to 80%||40% to 60%||40% to 50%|
|LIGHT SCHEDULE||18/6 recommended||18/6 for optimum growth but could try 16/8 or 20/4||12/12 consistently.|
|NUTRIENTS||Minimal to no nutrients, depending on grow medium||High nitrogen and low phosphorus and potassium||High phosphorus and potassium and low nitrogen|
|HOW LONG IT TAKES||2 to 3 weeks||3 to 15 weeks||7 to 14 weeks|
For more information read our full guide on how to harvest marijuana for perfect buds.
Marijuana plants come in different shapes and sizes, sativas are very tall sometimes reaching up to 20 feet if grown outdoors, whereas an average indica will reach around 6 feet and an autoflower 3 feet. An average height of a marijuana plant could be anywhere between 15 – 30cm tall after 4 weeks. But I wouldn’t put too much focus on height at this stage as some varieties tend grow faster during the later vegetative stage of growth. Providing the plant looks healthy and is growing consistently then you are okay.