If you’ve made it past part one and part two of our “How To Grow Weed Indoors” series, it’s time to dive into caring for your plants through their different stages of growth. Cannabis plants will go through a seedling, vegetative, and finally, flowering stage. Each stage requires unique care, so it is crucial to understand each part of the growth cycle to produce healthy plants.

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Once your cannabis seeds have successfully sprouted, they can be planted in your chosen medium. They should just be a few millimeters below the surface of your medium. These little plant babies are delicate and prone to damage if you do not handle them with care. Try to plant them with the roots facing downwards as an easy way to give them stability.

Seedling Stage

Small medical marijuana seedlings at a medical marijuana grow operation. iStock / Photographer, Videographer, Writer

Unlike later stages, cannabis in the seedling stage does not require as intense of a lighting setup. Compact fluorescent lights or LEDs should do the trick. The optimal light cycle for seedlings is 18 hours on and six hours off.

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Seedlings are tiny and fragile, so you should water them accordingly. Overwatering your seedlings is a major rookie move that can wreak havoc on your whole operation. Make sure the temperature of the room they are growing in stays between 68 and 77 degrees as that is their sweet spot. Humidity is important at this stage and some growers use humidity domes to keep the seedlings in their comfort zone.

Managing seedlings in small containers and then transplanting them to their permanent container during the vegetative stage is common. This stage should last about two to three weeks.

Vegetative Stage

This stage is where growing gets exciting. You’ll know you’re in the vegetative stage when the plants have developed strong roots and leaves. Be sure to carefully transplant them into their bigger containers if necessary when you reach this stage, as they will begin to rapidly grow.

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Plant growth cycles through a series where new leaves pop up frequently, usually stopping at around 10 leaves. Branches may start to develop, and expand in new directions.  Make sure to space your plants according to their expected growth depending on if they are indica, sativa, or hybrid. During the vegetative stage, you can begin to train your plants by pinching or “topping” them, which typically ends up increasing your yields.

Plants will stay in the vegetative stage longer if they are exposed to more sunlight. Growing indoors gives you complete control of how they stay in this stage. If you want them to stay in the vegetative stage and not flower, you can keep them in the same light cycle as the seedling stage (18 hours on, six hours off.) If you don’t have a lot of room, be careful how long you keep your plants in the vegetative stage. The longer they are kept without flowering, the larger the plants will become.

Plants will typically stay in this stage anywhere from three to 16 weeks.

how to grow weed iStock / PierceHSmith

Keep The Males Away

Before moving to the flowering stage, be sure to determine if you have any male plants in the mix. If you do, you’ll want to throw those buddies out because they’re going to try to pollinate your plants, forcing the females to produce seeds. You’re trying to get them to flower, not go to seed.

Female plants have pointy green calyxes, tear-shaped flowers that grow little white pistils. Males will not have this characteristic and instead will have small pockets filled with pollen. Make sure you separate any males from your bunch before the pockets of pollen burst.

If you don’t want to deal with separating the male plants out, consider using feminized cannabis seeds.

Flowering Stage

Pat yourself on the back for making it to the final stage. Flowering begins when you cut back on the light, reducing it to about 10-12 hours per day. When you make this adjustment, plants will sometimes have a growth spurt as they anticipate the coming of winter. Be sure to have enough space for this possibility.

The plants will begin to develop resiny buds. At this point, the plant is going to require more nutrients. It’s important to not abruptly change your schedule, and instead, ease from using growing to flowering nutrients over the course of a week or so.

Around the third or fourth week of flowering, your plants will stop growing altogether. Now they can focus all of their energy on making dense, aromatic buds loaded with trichomes.

Harvest time will vary, but somewhere between week six and eight is a good time to prepare. Don’t rely on numbers to know when you should harvest, as too many factors are at play. Try determining harvest time by looking at the pistils and trichomes on your plants.

The pistils, or tiny hairs, should change from white to yellow until they are finally brown. This can vary slightly depending on the strain you are growing. To look at the trichomes, a heavily-magnified item such as a jeweler’s loupe can be used to zoom in to the tiny appendages. Clear trichomes mean the plant is not ready, milky means they are at peak THC levels, and amber means they are beginning to decrease in THC levels.

Closeup of cannabis or marihuana plant. iStock / valbu

Tips For Successful Indoor Growth

Be sure to diligently follow directions as labeled on your nutrients and check for specific variations in growth for the strain you plan to harvest. Don’t prune your plants after a few weeks into the flowering stage as it can throw off their hormonal processes.

It’s important to stick to your light regimen precisely, as exposing your plants to light during their typical cycle of darkness can mess up the flowering stage. If you can’t stop yourself from peeking at your plants during their “night”, you’re going to hurt your yield.