There are a number of changes to consider once plants go from the vegetative stage to the flowering stage:
Within the flowering stage, there are three subphases:
Seedling stage length: 2-3 weeks
Marijuana light cycle: 12 hours a day
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 cycle will dictate when to prune, train, and trellis your plants, and when to harvest.
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 needed for the plant to become healthy and stable.
Marijuana light cycle: indoor—16 hours a day; outdoor—at least 6 hours of direct sunlight (“full sun”), plus several hours indirect sunlight
Even when your plant is a mere seed, the work you put in will dictate its success or failure. Germination is the stage when the first root cracks out of the seed’s shell, which takes between 1–7 days. The wet paper towel method is a classic approach here, but you start out with the major setback of tiny fibres all over your new root. You can plant directly in the soil, of course, but you need to ensure temperature and moisture are dialled in.
Autos really only flower for 30-45 days with a much more sudden transition into flowering, choosing feminised autos is a wise choice for novices that don’t want a seeded stash.
The main marker of a photoperiod plant is the potential for indefinite vegetation—as long as you keep the plants on an 18/6–24/0 light/dark cycle. We’ll talk more about that later, but it means these plants can withstand more mistakes in the growing process. It also means you can ensure your plant produces the best crop possible once you initiate flowering. All you need to do to make the switch is adjust the light cycle to 12/12. This becomes even more useful when you’re able to make unlimited clones of your optimised plant. The main drawback is that it’ll take around four months to get a substantial yield. However, you’ll have a larger and usually more potent plant once you’re there.
Looking for shifts in trichome appearance is the most accurate way to determine the stage of maturity of your crop. Trichomes are hard to miss and appear as a white frosty substance that covers the buds and sugar leaves. Zooming in on these structures will allow you to know how far along your plants are, and whether they are ready for the chop.
Photoperiod strains can be kept in vegetative growth indefinitely so long as 18+ hours of light and suitable conditions prevail. This is what allows indoor growers to keep mother plants for years and why outdoor grower’s plant in springtime. Indoors or outdoors 18+ hours of light facilitates taking cuttings too.
Those pistils will begin developing larger and larger and become darker in color. This is also when the odor from the plant becomes very apparent, so a good filtration system is a must at this point for indoor growth.
The final stage of flowering will have begun at this point for most plants, and the length of time can be variable. Buds will begin to grow very quickly now, seemingly overnight turning into dense flowers all over the plant.
Buds will not have grown too much at this point, so don’t worry if they are still fairly small.
15-16 week-old plant
It will grow a bit taller and begin to straighten up during this week. The very first new growths will appear as well, which will be another leaf along with the development of additional blades on the current leaves. Initially, they will be quite small.
This is where it all begins, the seed. During this formative stage of growth the cannabis seed, once planted or placed in a germination station, breaks apart and the spindly taproot emerges looking for nutrients.
It can last anywhere from 3-16 weeks, so knowledge of the particular strain being used is crucial here.
The rest of the growth is up to the plant, but when it seems to be getting close to harvest time flushing nutrients is important for quality tasting harvest. Simply flush the plants with pH-balanced water and stop administering nutrients at this time to ensure a good harvest.