The Vegetation Stage of Cannabis

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The Vegetation Stage of Cannabis – From Sprout to the Stretch thumbnail

From Sprout to the stretch

Hi there and welcome (back) to Free The Tree!
In this 2nd episode of the cycle of life of Weed we’re going to cover the Vegetative Stage, Aka the Growth Stage or Vegetation Stage.
This is where you’ll see the bulk of the growth of your plants. It is also generally the period where most of the plant training goes on.
Here’s what we’re going to cover:

What are the characteristics of the Vegetative stage?

GrowthSteady growth during the period.
Make sur to cut the branches that won’t get enough light as the plant grows.
Better to have a few strong branches than a bunch of week ones
Branch and leaf densityIn sequence she will produce 2 new leaves, 2 new branches
HumidityGoing down over time, it should start at around 65/70% humidity, ending around 50%
TemperatureReally during her whole life you should aim around between 19°C and 25°C
I know, I know, not easy sometimes….

During this stage you will need to give her mainly Nitrogen.

Phosphorous and Potassium are 2 other vital nutrients for her grow, but we’ll go over that in detail further below.

(Light cycle)
Keep about 18hours of light and 6 hours of night
Length in timeAs long as you want or your plant is vegged out. As long as you don’t switch the length of light exposure they will stay in this mode

During this stage you must make sure to give the plant enough Nitrogen nutrients.
In order to get the right measure you really have to test and learn with the strain you have, although I have found that going a little under the dosage given in the bottle works out pretty well.

Quick Warning : After the stretch the plan reduces its intake of nitrogen, making it real difficult to fight nitrogen deficiencies during the flowering stage.
I’m not saying go all out on Nitrogen!! Get hit with nutrient burn or Nitrogen toxicity and you’ve got a whole other set of issues on your hand!

Growth of the first set of leaves

During the first week or two of the vegetation stage you’ll see your plate start growing her first stage, composed of 2 main leaves and 2 side leaves. This is pretty unique since the following stages will generally be composed of 2 leaves and 2 side branches.

These first sets of leave will be what her energy source in order to grow into a strong plant.
These leaves will continue growing but will die at some point, don’t worry it’s normal.
When I say die I mean that they will show some form of deficiency, generally Nitrogen, once the plant has grown more.

First stage composed of 4 leaves growing
First set of leaves growing

Marijuana Vegetation – Growth of multiple levels

Once your Cannabis plant has grown her first stage she will keep on growing vertically towards the light source. This is true for the Apex as well as the side branches.
Each the “knot” (intersection where leaves and side branches grow) should be composed of 2 leaves and 2 side. Depending on how you’re training yor plant, if at all, you’re response at each knot may be different.

Apart from plant training, at this point you just want to let your plant grow strong enough in order to handle the buds that will come later on.

As you can see in the image on the right has side, this plant has grown over 5 stages so far. We’ve been training it to grow one main step by cutting all side branches since she was a slow grower and we needed her to catch up and reach the screen. She was so late we were really scare she wouldn’t be able to get enough light… The thing for sure is that we won’t be able to scrog that one very much.

You can keep this going on as long as you like, just keep in mind that there’s at least 3 times more roots, so the longer the vegetative stage, the bigger the pots needed.

Cannabis growth

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Root activity during the Vegetation Stage

During this stage what you see in growth above the pot is actually just a small part of the story.
Your plant is much more active within the soil, developing its root system in order to be able to extract all the nutrients needed.

As a rule of thumb, think that there’s 3 times more roots than what you see above the soil. These roots are as important, if not more, as the use of leaves for photosynthesis so you really have to make sure they have all the environment needed to thrive.

Keep an eye on her and don’t waste time hesitating to transplant her into larger pots, in that sens it’s better too early than too late. Check out our transplantation guide over here if you want more details.

Compressed roots at the bottom of soil
Waited too long to transplant

What Nutrients during the Vegetative Stage?

During the vegetative stage your Plant will principally need 3 elements Nitrogen, Phosphorous and Potassium. These 3 elements are vital to the well being of your plants and we will cover below what they uses are.

Before we get into that you might be wondering how much nutrients you need to be giving your plant. Unfortunately with Marijuana, and plants in general, there’s no “one rule fits all” do to the different types of nutrients out there and the different needs per strain.

Our advice is to follow the indications given with your nutrient pack. In our case we always start under the minimum advertised and see how the plants react, then adjust if needed.

We figure its better to have a little deficiency at first instead of dealing with nutrient burn.

What does Cannabis use Nitrogen (N) for?

Nitrogen is so vital to plants since it’s one of the major components of Chlorophyll, the compound that plants use for photosynthesis.
Furthermore, Nitrogen is one of the main components of Amino acids, the building blocks of Proteins.

What does Phosphorous (P) do in Marijuana?

Phosphorus (P) is one of the components of the complex nucleic acid structure of plants (aka genetic material) that regulates the synthesis of Proteins.

This means that Phosphorous is used for cell division and the development of new tissues.
Its last use of in plants is its link with the energy transformation in the plant.

Image credit to

How is Potassium (K) used by Weed?

Potassium (K) is the third vital element for plant development. This nutrient is used to regulate the opening and closing of the stomata, thus regulating the CO2 uptake of the plant.
It’s also responsible to trigger the activation of enzymes and involved in the production of Adenosine Triphosphate (ATP).

This last involvement might actually be more important in the regulation of the rate of photosynthesis than its role in the activity of stomata’s.

For more on the role of Potassium in the growth of plants check out this paper done by the International Plant Nutrition Institute, and for more info check out their website.

Cannabis use of NPK – Recap 

Nitrogen (N)
  • Production of new cells and enzymes
  • Needed for Chlorophyll production (green pigment)
  • Responsible for leaf and Stem Growth
Potassium (K)
  • Encourages uptake of water
  • Essential for the development of flowers
  • Increases resistance to diseases
  • Help plants regulate and make better use of light and air (photosynthesis and respiration)
Phosphorous (P)
  • Depending on the stage, it encourages root growth or flower blooming
  • Essential part of the photosynthesis process
  • Involved in the formation of sugars, starches and all oils.
  • Helps with the transformation of solar energy to chemical energy (photosynthesis)
Organic Nitrogen, Potassium and Phosphorus nutrient mixes
Bio Bizz Organic Nutrients
General Hydroponics full nutrient range

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Transplanting during the Growth Stage

As we started to say earlier, during the vegetation period the roots of the plants grow 2 to 3 times more in volume than the visible section, but “unlike” the leaves and stems they cannot grow infinitely.

The last thing you want is to have roots compressed, circling around the pot and growing out of the bottom.
Remember, your plant is only as good as her root system, if it’s too weak, or compressed, she won’t be able to get all the nutrients needed in the soil. Less nutrients = slower growth or smaller buds, so not good!

Depending on the size of your different pots you’ll want to transplant once or twice during her growth. Remember that this is one of the most stressful things possible, although necessary, so transplant her as few times as possible.

Note: I hear you, why not plant them right away in their final pots? You can totally do so, it’s something we’re doing in our current grow. Just be aware that the early (visible) growth will be much slower and it may stretch the vegetative stage a week of two longer.

When to start the Flowering Stage

If you’re looking for a precise answer you might be disappointed.. There’s no rule here, you can kind of do as you wish.
What we can do though is give you a couple pointers in order to pick your right moment to get the flowering stage going, here it goes:

  • Your plant is “vegged out”, meaning that your plants growth is slowing down.
    If you notice this, your plant is most likely ready to get producing some buds 🙂
  • Your plant is getting tall. Remember your plant will grow between 50% to 200% of her size, depending on her phenotype, during the stretch.
    If you think they’ll be too tall and close to the light, you want to get going.
  • You’re plant training is about finished.
    As we said above, during the stretch she’ll keep growing, meaning that she should be perfect by the end for what you’re looking for.
  • You might not be around after the flowering stage.
    Remember that after the flowering stage you have about 3 weeks of curing. During those 2 last weeks you need to be around to open the containers and let the humidity out every day/other day.

Now that we’ve given you a couple pointers on when to flower your plants here’s some when not to do so. This may just save you the harvest!

The stretch is about to start, close up on the first signs
First signs of the start of the Flowering Stage

When NOT to start the Flowering Stage

In some situations you actually want to avoid entering the flowering stage. The flowering stage is a sensitive one. Since Cannabis is a “one task” plant, during the flowering stage she won’t really focus on leaf development, meaning that any issues are much harder to catch up.

Here’s the main situations where you should keep the vegetation stage going until it’s fixed:

  • The Plant is showing deficiencies: As we said in the introduction, after the stretch your plant is going to concentrate her energy on the flowers.
    If you have a deficiency going on and losing leaf mass, it might be best to fix the issue, let the plant recover and grow new sets of leaves and then change the photo-period.
  • Your Cannabis Plant is showing root issues: Although the roots will strongly reduce their growth once you’re out of the growth stage, you don’t want them to be compressed and tight in the pot.
    On top of that, during the stretch and throughout the flower period they do keep growing a little.
    Our advice would be to transplant them, wait a couple days for them to recover and grow into the new soil before switching them to 12/12.
Plan taking in the nitrogen from the leaf
Leaf showing sign of deficiency
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Alright folks that’s all for this one! In the next series we’ll be covering the different steps of the flowering stage.
Until then, be safe and grow easy!


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