How to Care for a Cannabis Plant at Every Stage of Growth

A cannabis plant goes through four growth stages, germination, seedling, vegetative and flowering, before harvest, and each one needs different care: moisture for the seed, gentle watering for seedlings, lots of nutrients in veg and a light change plus bloom feed in flower. Getting that care right at each step is the key to a healthy plant and a solid harvest.

As it grows, a weed plant goes through changes that call for different kinds of care. So here's a rundown of each stage and what makes it tick.

Germination stage:

It all starts with the seed. A healthy cannabis seed should feel hard and dry and be light to dark brown. An immature seed is usually soft and green or white, and it probably won't germinate.

This is where your plant's growth begins. Germination can take anywhere from 1 to 2 weeks, and it's the moment the plant is born. To make it happen, the seed needs water and moisture. When the seed cracks open and a white root pokes out (called the taproot), your cannabis plant has officially started growing.

The next step is planting the seed in soil, setting the root just slightly into the growing medium so the plant can take off. When the plant pushes out its first two little leaves, it's still pretty fragile, but once the leaves grow a bit more and take shape, your seed has become a seedling.

Seedling stage

The seedling stage lasts about 2 to 3 weeks, and it's when the plant develops its leaves. You'll see the first leaflets form, followed by the classic “fingers” of the cannabis leaf. A healthy seedling looks compact, with deep green, almost shiny leaves.

Cannabis seedlings do best in more humid conditions. Temperatures should be warm (ideally around 25 °C / 77 °F), so keep the lights close to the plants and raise them as the plants grow.

This is a stage where you really need to be careful not to overwater, because the roots are tiny and don't need much water to thrive. Seedlings are also vulnerable to disease and fungus, so keep their surroundings clean and watch out for excess moisture.

Even people who grow outdoors often start their plants indoors under grow lights to get them safely through this delicate stage.

Vegetative stage

This stage lasts 2 to 8 weeks, and it's when you'll see the most growth, so by now you should have transplanted into a bigger container. You'll need to water more, and you want to soak the whole container so the roots get thoroughly wet.

Plants in veg love nutrients, so this is the time to check what you're feeding them and how much. You can also figure out whether a plant is male or female by looking at the preflowers at the nodes. Females show little white hairs, and males show small balls. Remember: if you get a male, separate it so it doesn't pollinate your other plants.

The vegetative stage is a key part of a cannabis plant's life cycle. As a grower, your job is to give plants the best possible environment so they grow as big and healthy as possible. Size usually translates into harvest: the bigger the plants get, the more nodes, or bud sites, they'll develop.

Flowering stage

Depending on the strain, flowering can last roughly 6 to 8 weeks. The plant starts flowering when it gets less than 12 hours of light a day. At this stage, you can only prune until around the second week of flowering; after that, leave it alone. The buds will start weighing the plant down, so now's the time to add support so no branches snap. The fertilizer you give during this stage should be a bloom-specific formula.

Outdoors, flowering kicks in naturally as the plant gets less light each day while summer turns to fall. Indoor growers, on the other hand, trigger it by cutting the light their plants get from 16 to 18 hours down to 12 hours a day.

The nutrients plants need most at this stage are phosphorus and potassium (PK).

Harvest time

Harvest isn't technically part of the growth process, but knowing when to do it matters a lot. When the hairs (pistils) on the buds turn from white to orange or brown, it's a sign your plant is ready. The trichomes also change, going from clear to milky and then amber. Once the cycle is complete, many growers prefer to harvest in the morning, on the idea that the plant keeps building trichomes overnight.

The way you learn the most about your plants is by watching them and caring for them every day. Every plant and every grow teaches you something new, so you can keep sharpening your technique and getting better results from each cycle.

How long does it take to grow a cannabis plant?

Generally speaking, it takes roughly 12 to 24 weeks, or 3 to 6 months, to grow a plant from seed. The fastest route is starting with a clone or an autoflower seed.

You'll see the most variation in timing during the vegetative stage, after the seedling phase and before flowering.

If you're growing indoors, you can force a plant to flower after just a few weeks. Outdoors, though, you're at the mercy of the seasons, so you'll have to wait until the days start getting shorter as fall approaches for the plant to flower.