Best LED Grow Lights for Cannabis

The growth stages of marijuana can be broken down into four primary stages from seed to harvest:

• Germination (3-10 days)
• Seedling (2-3 weeks)
• Vegetative (3-16 weeks)
• Flowering (8-11 weeks)

Cannabis seed germination

Seed germination length: 3-10 days

Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors

The first marijuana plant stage begins with the seed. A cannabis seed should feel hard and dry, and be light- to dark-brown in color. An undeveloped seed is generally squishy and green or white in color and likely won’t germinate.

Once your seed has germinated, or sprouted, it’s ready to be placed in a growing medium, like soil. The tap root will drive down while the stem of the seedling will grow upward. 

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 so the plant can grow healthy and stable.

As roots develop, the stalk will rise and you’ll begin to see the first iconic fan leaves grow, at which point your cannabis plant can be considered a seedling.        

Seedling stage in cannabis plants

Seedling stage length: 2-3 weeks

Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors

When your marijuana plant becomes a seedling, you’ll notice it developing the traditional cannabis fan leaves. As a sprout, the seed will initially produce leaves with only one ridged blade.

Once new growth develops, the leaves will develop more blades, or “fingers” (3, 5, 7, etc.). A mature cannabis plant will have between 5 or 7 blades per leaf, but some plants may have more.

Cannabis plants are considered seedlings until they begin to develop leaves with the full number of blades on new fan leaves. A healthy seedling should be a vibrant green color. 

Be careful to not overwater the plant in its seedling stage—its roots are so small, it doesn’t need much water to thrive.

At this stage, the plant is vulnerable to disease and mold. Keep its environment clean and monitor excess moisture. Be sure to give it plenty of light.

Even if growing outdoors, a lot of growers will start their seeds inside under an artificial light to help them through this delicate stage of marijuana growth.

If you buy a clone from a grower or breeder it will be a seedling, so you can skip the seed germination phase.

Vegetative stage in cannabis plants

Vegetative stage length: 3-16 weeks

Marijuana light cycle: 18 hours a day indoors; full, direct sun 6 hours a day outdoors

The vegetative stage of cannabis is where the plant’s growth truly takes off, and it typically lasts 3-16 weeks. At this point, you’ve transplanted your plant into a larger pot and the roots and foliage are developing rapidly. This is also the time to begin topping or training your plants.

Be mindful to increase your watering as the plant develops. When it’s young, your plant will need water close to the stalk, but as it grows the roots will also grow outward, so start watering further away from the stalk in the soil so roots can stretch out and absorb water more efficiently.

Vegetative plants appreciate healthy soil with nutrients. Feed them with a high level of nitrogen at this stage.

If you need to determine the sex of your plants (to discard the males), they will start showing sex organs a few weeks into the veg stage. It’s imperative to separate males so they don’t pollinate the females.

Cannabis plant flowering stage

Flowering stage length: 8-11 weeks

Marijuana light cycle: 12 hours a day indoors; full, direct sun 6 hours a day outdoors

The flowering stage is the final stage of growth for a cannabis plant. This is when plants start to develop resinous buds and your hard work will be realized. Most strains flower in 8-9 weeks, but some can take even longer, especially some sativas.

Outdoors, flowering occurs naturally when the plant receives less light each day as summer turns into fall.

Indoor growers can trigger the flowering cycle by reducing the amount of light marijuana plants receive from 18 to 12 hours a day.

There are three subphases of the flowering stage:

• Flower initiation (week 1-3): The plant will continue to grow and females will develop pre-flowers—pistils, or white hairs, will grow out, which are the beginnings of buds.
• Mid-flowering (week 4-5): The plant itself will stop growing and buds will start fattening up.
• Late flowering/ripening (week 6 and on): Trichome density will increase and plants will get very sticky; keep an eye on the color of the pistils to tell when to harvest.

There are a number of changes to consider once plants go from the vegetative stage to the flowering stage:

• Don’t prune when plants are flowering, as it can upset their hormones
• Plants should be trellised or scrogged so buds will be supported as they develop and air can flow through plants
• Consider giving plants bloom or phosphorus nutrients

When do buds grow the most?

Buds typically grow the most toward the end of the flowering life cycle. You probably won’t notice much budding out at the beginning of the flowering stage, and it will slow down toward the end of the cycle, when buds become fully formed.

Once buds have reached full maturation, it’s time to harvest your marijuana. How long it takes to harvest buds depends on many factors, including harvesting methods and how many plants you harvest.