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4 stages of cannabis plant growth

Cannabis plants go through a number of stages as they grow and mature, these different growth stages require different amounts of light, nutrients and water.

It is important to know these phases and how long each one lasts so that we know what the plant needs and when. Knowing where your cannabis plants are in their life cycles will determine when to prune, train and harvest your plants.

How long does it take to grow a cannabis plant?

Generally speaking, it takes 10-32 weeks or about 3-8 months to grow a weed plant from seed to harvest. It will be faster if you start with clone or autoflowering seed.

The greatest variability in how long a marijuana plant takes to grow occurs in the vegetative stage – after the seedling stage and before flowering.

If you’re growing indoors, you can force a weed plant to flower after a few weeks when it’s small, or after a few weeks when it’s big.

When growing outdoors, you are at the whim of the seasons and will have to wait until the sun begins to set in the fall for the plants to bloom and then harvest.

One way outdoor growers can control the flowering cycle is through the use of low light techniques.

What are the growth stages of a weed plant?

(Sasha Beck/Leafly)

The growing stages of marijuana can be divided into four primary stages from seed to harvest:

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

Cannabis seed germination

Seed germination time: 3-10 days

Light cycle of marijuana: 18 hours a day indoors; full, direct sun 6 hours a day outside

The first stage of the marijuana plant begins with the seed. The hemp seed should be hard and dry and light to dark brown in color.

Once your seed has germinated, it is ready to be placed in a growing medium such as soil. The root goes down, while the stem of the seedling grows up.

As the plant unfolds from the protective seed coat, two round “womb” leaves grow from the stem. These initial leaves receive sunlight so the plant can grow healthy and steady.

As the roots develop, the stem rises and you begin to see the first iconic fan leaves grow, at this point your cannabis plant can be considered a seedling.

Can you speed up the germination process?

No. Hemp seeds are delicate and do not like to be handled. They need a warm environment without temperature fluctuations and not too much water. Once you put them in the soil, leave them alone.

Quality seeds usually have a high germination rate, but you may get some rot that won’t germinate. Let them do their thing; helping them can reduce their chances of survival.

Seedling stage in cannabis plants

Duration of seedling phase: 2-3 weeks

Light cycle of marijuana: 18 hours a day indoors; full, direct sun 6 hours a day outside

When your marijuana plant becomes a seedling, you will notice that it develops the traditional cannabis fan leaves. As a sprout, the seed initially produces leaves with only one comb blade.

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

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

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

At this stage, the plant is susceptible to diseases and fungi. Keep its environment clean and watch for excessive humidity. Be sure to give it enough light.

Even though they are growing outdoors, many growers will start their seeds indoors under artificial light to help them get through this delicate phase of marijuana growth.

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

Vegetative stage in cannabis plants

Duration of the vegetative stage: 3-16 weeks

Light cycle of marijuana: 18 hours a day indoors; full, direct sun 6 hours a day outside


The vegetative stage of cannabis is where the growth of the plant really takes off and usually lasts 3-16 weeks. At this point you have transplanted the plant into a larger pot and the roots and leaves are developing rapidly. This is also the time to start watering or training your plants.

Remember to increase watering as the plant develops. When young, the plant needs water close to the stem, but as it grows, the roots will also grow outward, so start watering further away from the stem in the soil to allow the roots to stretch out and absorb water more effectively.

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

The flowering stage of the cannabis plant

Length of flowering phase: 8-11 weeks

Light cycle of marijuana: 12 hours a day indoors; full, direct sun 6 hours a day outside

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

It blooms naturally outdoors 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 that marijuana plants receive from 18 to 12 hours a day.

There are three sub-phases of the flowering phase:

  • Flower initiation (weeks 1-3): The plant continues to grow and the female flowers develop pre-flowers – pistils, or white hairs, which are the beginnings of buds.
  • Mid-flowering (week 4-5): The plant itself stops growing and the buds begin to fatten.
  • Late flowering/ripening (6 weeks and beyond): Trichomes density will increase and plants will be very sticky; watch the color of the pistils to know when to harvest.

As plants transition from the vegetative phase to the flowering phase, we need to consider a number of changes:

  • Do not prune when the plants are in bloom as this can disrupt their hormones
  • Plants should be trellised or crushed to support the buds as they develop and to allow air to flow through the plants
  • Consider giving your plants a bloom or phosphorus nutrient

What does the pre-flowering phase look like?

The primroses are the beginnings of the sexual organs of cannabis plants. If we are growing regular seeds, it will likely be a mix of male and female plants and we will need to determine the sex of our plants in order to discard the males. It is necessary to separate the males so that they do not burn the females.

The pre-flowers appear at the nodes of the plant where a branch grows from the main stem. Females develop an oval bract with protruding hairs or pistils, while males develop round pollen sacs.

Learn more about the pre-flowering and sexing of cannabis plants in our anatomy article.

How to find out when a plant starts to grow?

When grown outdoors, weed plants begin to bloom or bloom after the summer solstice, when the amount of daylight begins to wane. The plant will begin to have pre-flowers as shown above, giving you an indication that flowering has begun.

When growing indoors, growers choose to force bloom or “knock” the plants into flower by cutting off the amount of artificial light they receive.

What to do if cannabis plants flower early or late

The harvest will depend on the strain. Indicas usually finish early and sativas finish late.

Note the information from the breeder when buying seeds to grow to get an idea of how long it takes to flower. Some plants are harvested earlier and some later depending on when they are finished.

For late blooming strains, watch the weather to make sure the cold weather doesn’t kill your plants before they finish.

When do the buds grow the most?

Buds usually grow the most towards the end of the flowering life cycle. You probably won’t see much budding at the beginning of the flowering phase and it will slow down towards the end of the cycle when the buds are fully formed.

Once the buds have reached full maturity, it’s time to harvest the marijuana. How long it takes to harvest buds depends on many factors, including harvesting methods and the number of plants you harvest.

How long can a marijuana plant live?

Weed plants are annuals, meaning they grow and live for one season and then die. Wild cannabis plants grow seeds and drop them when they die, then grow more in the following years.

At harvest, the plants are cut down and die to obtain the buds.

If left unharvested, the weed plants will eventually wither and rot within months of peak flowering.

When should you grow marijuana?


If you are growing outdoors in the Northern Hemisphere, growers usually obtain seeds between February and April and germinate the seeds by the end of April.

Many will start by growing the seedlings indoors in a more controlled environment, as the seedlings are more delicate, and then put them in the ground outside once they are a little bigger and the weather is warmer.

If you are growing clones or autoflowering plants, you have a grace period of about another month. Plants usually need to be outside, in the ground, by the end of June.

The harvest takes place sometime between September and November. This depends on your local climate as well as the weather of the year.

If you grow grass indoors, you can grow it whenever you want. Keep in mind that the outdoor environment will affect your grow space – you may need to add heaters in the winter or fans and air conditioning in the summer.

Important dates for growing marijuana outdoors

Many growers start germinating seeds as early as February and March to give the big plants time to harvest, but the spring equinox is a good reminder that it’s time to start the outdoor growing process and start germinating seeds if you haven’t already.

Many farmers wait until after Mother’s Day in May to place their plants outside. Just make sure all your plants are outside by the summer solstice at the latest.

The weather will begin to turn and the sun will begin to lower in the sky as your plants fatten up with sweet, sticky buds. It may be tempting, but the autumnal equinox is about when to start harvesting. It will depend on your climate and the year – it may happen a little earlier or later.

Everything should be cleaned, dried and cured by Thanksgiving and in some places even by Halloween.

As winter approaches, it’s high time to make your own hemp butter, topicals, or tinctures with all that scrap from the harvest. Kick up your feet, relax and hunker down for the winter, it’s been a long growing season!

Notes on Marijuana Growth Stages

You will need to adjust the growing conditions based on your specific region and local weather and climate.

Don’t forget to keep a grow log to track the progress of your plants. Reviewing your notes will help you learn from mistakes and maximize the quality and quantity of your buds next year.

Take careful notes of when and how you do each step and note:

  • Weather
  • How much water you give the plants and at what intervals
  • Amount of nutrients
  • When up and pruning

Pictures will also give you a better idea of how your plants look along the way.

Information drawn from: https://www.leafly.com/learn/growing/marijuana-growth-stages

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