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how tall does marijuana grow

4 stages of marijuana plant growth

Cannabis plants go through a series of stages as they grow and mature, and those different growth stages call for different amounts of light, nutrients, and water.

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.

How long does it take to grow a marijuana plant?

Generally speaking, it takes anywhere from 10-32 weeks, or about 3-8 months, to grow a weed plant from seed. It’ll be quicker if you start with a clone or an autoflower seed.

The biggest variability in how long a marijuana plant takes to grow will happen in the vegetative stage—after the seedling phase and before flowering.

If you’re growing indoors, you can force a weed plant to flower after only a few weeks when it’s small, or after several weeks when it’s big. If you’re growing outdoors, you’re at the whim of the seasons and will have to wait until the sun starts to go down in fall for it to flower and then to harvest.

When should you grow marijuana?

If you’re growing outdoors in the Northern Hemisphere, growers usually get their seeds between February and April, and you should start your seeds by the end of April. Some growers will start their seedlings inside in a more controlled environment because seedlings are more delicate, and then put their seeds in the ground outside once they’re a little bigger. If you’re growing clones or autoflowers, you have a grace period of another month or so. Plants usually need to be outside, in the ground, by the end of June.

Harvest happens sometime between September and November. This depends on your local climate, as well as the weather that particular year—one year it could be the end of September, the next, end of October, and growers in the Pacific Northwest will have to pull down their crops earlier than those in Northern California.

If you’re growing weed indoors, you can grow whenever you like. Keep in mind that the outside environment will affect your grow space—you may need to add heaters in the winter or fans and ACs in the summer. Other than that, you can start seeds whenever you like and flip them into flower whenever you like, depending on how big you want the plants.

Important dates for growing marijuana outdoors

The Spring Equinox is a good reminder that it’s time to kick off the outdoor growing process and start germinating your seeds.

As the sun reaches up high in the sky, your cannabis will want to as well. Make sure all of your plants are outside by the Summer Solstice.

The weather will start to turn and the sun will begin descending in the sky as your plants fatten up with sweet, sticky buds. It might be tempting, but wait until around the Fall Equinox to start harvesting.

Everything should be cleaned up, dried, and curing well before the Winter Solstice. Now’s a good time to make your own cannabutter, topicals, or tinctures with all that trim from the harvest. Kick your feet up, relax, and hunker down for the cold, it’s been a long growing season!

Notes on marijuana growth phases

We can’t stress enough that the timeframes in the above graphic are ranges of time for the Northern Hemisphere. You’ll need to adjust them based on your specific region and local weather and climate.

Be sure to keep a grow journal to track the progress of your plants. Looking back on your notes will help you learn from mistakes and maximize the quality and quantity of your buds.

Take meticulous notes on when and how you perform each step, as well as what the weather is like. Other notes can include how much water you give plants, at what intervals, and how much nutrients you give them. Pictures will also give you a better sense of how your plants look along the way.

What are a weed plant’s growth stages?

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)

Seed germination

Seed germination length: 3-10 days

Marijuana light cycle: 16 hours a day

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 needed for the plant to become 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

Seedling stage length: 2-3 weeks

Marijuana light cycle: 16 hours a day

When your marijuana plant becomes a seedling, you’ll notice it developing more of 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 (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 very 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

Vegetative stage length: 3-16 weeks

Marijuana light cycle: indoor—16 hours a day; outdoor—at least 8 hours of direct sunlight (“full sun”), plus several hours indirect sunlight

The vegetative stage of cannabis is where the plant’s growth truly takes off. 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 higher 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.

Flowering stage

Flowering stage length: 8-11 weeks

Marijuana light cycle: 12 hours a day

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 16 to 12 hours a day.

Within the flowering stage, there are three subphases:

  • 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 stage, as it can upset their hormones
  • Plants should be trellised so buds will be supported as they develop
  • Consider giving plants bloom (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.

Pat Goggins and Trevor Hennings contributed to this article.

Knowing where your cannabis plants are in their life cycle will dictate when to prune, train, and trellis your plants, and when to harvest. Learn more about marijuana growth stages today.

Question: How tall do weed plants grow

When considering the question of how tall do weed plants grow, the answer is really as long as a piece of string – or perhaps a joint of weed! There is an enormous variation between different strains of cannabis – from compact bushes to leggy giants – and how they are grown can also make a difference to the overall height. Let’s look at the heights you can expect a typical weed plant to achieve when grown indoors or outside, and the impact various techniques can have on height.

Sativas, Indicas and Ruderalis

These are two main strains of cannabis, although there are many hybrids which combine genetics from both. There are many visual differences between Sativas and Indicas, and one of the most obvious is height. Sativas can grow extremely tall, to twenty feet and is slower to grow and reach harvest. Indicas are compact, bushy plants that typically reach heights of between three to six feet. Hybrids vary enormously; we recommend reading information about the strain before your purchase to find out whether Satia or Indica is dominant when it comes to potential growth. The other strain of cannabis is Ruderalis, whose genetics are often found in autoflowers, and this is also a short plant similar in size and shape to Indica.

Cannabis height when grown outside

If you were to leave a Cannabis Ruderalis strain to grow outdoors in favourable conditions completely unchecked, a single plant could easily achieve heights of 20 feet and a breadth of two to three feet. The only limitations are the amount of root space in the soil and the number of hours light in a day. If you have the space and inclination, it is easily possible to grow a forest of truly gigantic weed plants.

Cannabis propensity to grow means that its height needs to be carefully controlled by you, the grower, without affecting the health of the plants and the quality of the yield.

The optimal height for weed grown indoors

If you cultivate your cannabis plants indoors, their final height is in your hands. Although it may seem contrary, it is not worthwhile allowing your plants to get past a certain height, unless you have enough grow space. There are several reasons for this:

  1. The largest buds are found at the top of the plant nearest the light source. Buds get progressively smaller down the plant. To maximize yields, you need to ensure that light can penetrate as much of the plant as possible, which is where the various training methods come in.
  2. Extra growth results in a long, lanky plant without any extra yield, which is really a waste of time, money and electricity!
  3. Plants that are too tall can attract unwanted attention when grown outdoors or if there is limited indoor space.

There are several methods you can use to control the height of your weed plants:

  1. Low Stress Training (LST)
  2. Screen of Green (Scrog)
  3. Topping

1. Low Stress Training (LST)

LST is an easy and inexpensive method of training that simply involves bending the growing stems in the direction you want them to grow and gently tieing them in place. LST enables light to reach more buds by creating a more even canopy.

2. Screen of Green (ScroG)

ScroG works similarly to LST but involves a screen, net or trellis against which the cannabis plant is encouraged to grow horizontally. This method also creates more budding sites by stretching out branches to expose more nodes to the light.

3. Topping

Topping a type of pruning that takes place just before the plants enter the flowering phase. Get some pruning shears and top all the branches to rein in the stretch that takes place during the flowering phase. This might sound drastic but will encourage the plants to focus their energies on producing flower heads rather than wasting energy on growing upwards.

Follow these tips to prune safely:

  1. Wait for a minimum of 3 layers of leaves before cutting;
  2. Always use a pair of clean, sharp scissors or secateurs;
  3. After cutting, there should always be enough leaves left to allow the plant to breathe and photosynthesize;
  4. Don’t worry if the new growth turns light green after cutting; this is normal!

There really isn’t an optimal height for cannabis, it depends on your personal preference, space and growing set up. Ultimately, if you want to maximise your yields, it pays to learn as much about the strain as possible, and this includes expected height.

Curious how big weed plants grow indoors or outdoors? Check it out and find all the answers you need!