The Life Cycle of the Cannabis Plant
How long does it take to grow cannabis?
While there are many factors that affect the life cycle of a cannabis plant, most cultivators witness the same growth patterns. Cannabis will start as a single seed, then move to germination, to a seedling, to vegetation, to flowering, and finally, to harvest. Each phase of this life cycle has a unique set of ideal growing conditions, which concern the level of nutrients, light, and even water.
The overall needs and growing conditions available, though, vary from facility to facility. This is particularly true when comparing indoor vs. outdoor cultivation. Indoor growers have more control over growing conditions to ensure optimal growth. However, even for outdoor cannabis, there are ways to control the process. For example, growers can restrict light access, altering the length of time plants spend in the vegetative state.
Overall, the full life cycle of a cannabis plant takes 4 to 8 months, as it develops from a mere seed to a mature adult plant. Outlined below are the stages of the cannabis life cycle, the specific plant care required, and other details pertinent to cannabis growth.
Phase One: Seed
Let’s say you’re holding a random assortment of cannabis seeds in your hand. They’re all going to look pretty much the same, even if they’re different strains or sexes. If they aren’t labeled based on sex, you might run into major issues later in the cultivation process. Before moving forward with germination, you need to trust that the seeds you’re working with are female only.
Why only females? Well, only female cannabis plants produce harvestable buds that dispensaries and patients will buy. So, not only do you want to ensure you have female plants grown to produce these buds; but you also want to avoid mixing male and female plants within the same spaces. Otherwise, you run the risk of male cannabis plants pollinating female plants near them. When female cannabis plants are pollinated, they use their available energy to focus on growing more seeds instead of the THC-filled buds that patients can enjoy so much.
Unless you’re trying to pollinate cannabis plants to produce seeds exclusively (instead of buds), keep the male plants out of the picture. If you do get your hands on some new seeds that you want to keep in stock, make sure you clearly label them by strain and sex!
Seeds should be stored in cool, dark spaces. The seeds you want will be hard, dry, and brown – not soft and white/green. Soft seeds have had exposure to too much moisture and are likely rotten or immature. When you’ve selected and inspected your desired seeds, it’s time to move into the germination stage.
Phase Two: Germination (3-10 days)
If you’re cultivating outdoors in the Northern Hemisphere, the ideal time of year to begin the full life cycle of the cannabis plant is the springtime. Then, you can expect the cannabis harvest to occur around autumn. For indoor cannabis cultivation, you can have several full growth cycles all year long.
Seeds moving to germination should still be stored in a dark area at first. Cultivators may have different procedures for germination. Some place the seed in a cup of water, and some use a damp towel to wrap around it. Keep the seed in this moisture for 24 hours before moving it to your chosen starter mix – not potting soil! A seed has enough of its own nutrition to keep it healthy for the first 2-3 weeks of growth. Typical potting soil is too rich in nutrients and can burn the seed before it even reaches maturity.
Once planted in this starter mix, a seed can take 3-10 days to sprout. You’ll know it’s sprouted when you can spot the two identifiable round seedling leaves, or “cotyledon” leaves. When these cotyledon leaves are visible and distinct, it’s time to move to the seedling phase. These leaves do need exposure to more light and nutrients, so this will be the time for you to place the plant in soil.
Phase Three: Seedling (2-3 weeks)
When the noticeable cotyledon leaves start stretching to any available light, your baby cannabis plant will start to show signs of other leaf growth, too. These new leaves won’t be round, though. They’ll be serrated like the recognizable marijuana leaf. A typical seedling will grow 4-8 individual leaves (which develop in pairs). At first, these tiny, jagged leaves will be rounded until they start to branch off into different “fingers” on each leaf. It’s the seven-fingered serrated marijuana leaf that the industry knows so well.
At this stage in the cannabis life cycle, your seedling will need a lot of light to encourage that leaf growth – about 18-24 hours of it per day. Seedlings also prefer moist soil and mild humidity. When watering seedlings, be intentional about not overwatering them. Instead, let each baby plant dry out before watering again. This prevents drowning them. This is critical as the plants are probably at their most vulnerable life phase while seedlings. Keep their environments clean and maintained to ensure pests or common plant diseases can’t get ahold of them.
Seedlings are also known as “clones.” In essence, these baby plants are just singular branches of the cannabis plant that can continue growing to full maturity. Seedlings are grown all the way from the seed stage, and clones are cut from the already mature cannabis plants to start as new babies altogether. Cannabis is categorized as a seedling until it grows up to 5-7 fingers on each leaf. Then, it’s time to up-pot the plant to give it more room to keep growing.
Phase Four: Vegetative (3-16 weeks)
Sometimes, the vegetative state is split up into a subcategory called “Pre-flowering.” Including pre-flowering, this phase of the cannabis life cycle can last anywhere from 1-4 months altogether. To initiate this stage, baby cannabis plants will be up-potted, typically into quart-sized cups. This allows the roots more room to keep stretching and growing. As the roots grow, so does the plant above the soil, reaching toward its source of light.
During this time, the plant will grow from approximately 8 inches in height to 2-3 feet. The ideal growing conditions for vegetative cannabis will be dryer than when it was a seedling, as well as with a lot more soil space and nutrients to encourage growth. If you’re in an outdoor space, the plants will need about 12-15 hours of natural light a day. For indoor cultivation, you’ll need to provide approximately 18 hours daily of fluorescent light. You’ll also still want to allow plants to dry out between watering cycles to ensure they’re not getting overwatered.
After about 6 weeks in this life stage, you should be able to determine the sex of your plant. (This is of particular value if you never labeled your seed as male/female in the beginning!) Females can be spotted by pistils that will jut off from the stem. Males, conversely, grow small green sacs full of pollen that can be found on node areas. (Nodes are angled areas where the branches grow off from the main stem.) If you can’t tell the difference between male and female cannabis plants at first, don’t worry. It just takes practice!
This is a critical step, though, as the female plants need to be unpollinated to produce the consumable THC-filled resin. These unpollinated plants are called “sinsemilla” females. Instead of diverting nutrients and energy to developing seeds, you can expect them to grow nice, bushy buds full of the coveted THC and other cannabinoids. The presence of these cannabinoids will be known by tiny white hairs appearing near the nodes of the plant.
This is also the time in a cannabis life cycle in which you can spot the difference between an Indica-leaning plant and a Sativa-leaning plant. Indica cannabis plants are shorter and bushier. Sativa cannabis, conversely, grows tall and lanky with less foliage. During the vegetative state, however long it is, it’s important to check weekly to ensure your cannabis plants have plenty of growth room. This is the time to top, trim, and train the plants to allow for that continued growth.
Phase Five: Flowering (8-11 weeks)
The flowering phase of the cannabis life cycle is one of the more exciting. It’s at this time when you’ll get the smell and sight of your potential finished medicine!
You’ll be able to control the duration of the vegetative state based on how much light you expose to your cannabis. When you reduce this amount of light (to about 12 hours for indoor grows and about 6 hours for outdoor grows), your plants will automatically start to move into the flowering stage. Flowering cannabis needs medium humidity and flowering-specific nutrient mixes.
Evidence of a cannabis plant moving into the flowering stage includes the presence of sticky resin, distinct strain-specific smells, and the colors of the plant’s pistils turning from white to reddish orange. This is a process that needs to be watched carefully – especially if you’re new to growing that specific strain. Strains vary in the length of time it takes to flower from 8 to 11 weeks, typically (it’s worth noting that Sativa strains are more likely to take longer to flower). Remember, don’t prune cannabis during the flowering phase, as it can upset the plant’s hormone balance and negatively affect the desired medicinal qualities.
You’ll also want to keep an eye on the plant’s trichomes. Trichomes are tiny resin-filled spheres that hold all cannabinoids, such as THC and CBD. Once the plant moves fully through the flowering stage, these trichomes will start to fall off. It’s essential that you harvest the flower before this happens! It takes practice to know the perfect day for harvesting a cannabis strain.