Vegetative stage in Cannabis plants: a guide for beginners

The Cannabis plant has two main stages in its life cycle: vegetative and flowering stages. In this article, you’ll learn about the vegetative stage, what happens after the seed sprouts and the seedling evolves into a young plant.

Not there yet? Read our article on Cannabis seedling and come back later!

Cannabis plant in the vegetative stage

After growing the first set of fan leaves with a complete set of leaflets, the plant goes from being a seedling to the vegetative stage. Now the plant grows only stems and leaves (not flowers or “buds”) and focuses all its energy on growing big and strong.

The plant has to grow its body with air, light and nutrients. The recently formed roots are now expanding into their growing medium, looking for water and nutrients. The roots also need air, so make sure there’s plenty of air spaces in the substrate!

How long does vegetative stage last in a Cannabis plant?

In the vegetative stage, a healthy Cannabis plant grows in height and size as much as it can with the given conditions. So the bigger the pot and the environment, the bigger the plant will be, provided it has the needed growing requirements.

The vegetative stage in Cannabis plants may last from 3 to 16 weeks, or even more in outdoor crops.

Most growers vegetate their indoor plants for 4-8 weeks, depending on the desired plant size. Cannabis plants are usually able to start flowering from the 4th week of the vegetative stage. Probably as a result those plants will be smaller in size. Consequently, giving your plants more vegetative time will result in bigger plants and more likely to produce higher yields. Cannabis plants may be left in the vegetative stage for a longer time, in order to take cuttings from it and make clones of that “mother plant”.

How does the Cannabis plant change stages? 

The answer is “photoperiod”. Photoperiodism is a response to the changes of duration in the cycles of light and dark periods. 

Cannabis is an annual plant. This means its flowering period is determined by the seasons (and their changing photoperiods). So, when the cycle ends, the plant dies.

In indoors, you must change your lights timer to a 12/12 hours schedule to trigger the flowering stage. By week 4-6 from seed, Cannabis plants are able to start showing their gender by growing preflowers.

Cannabis life cycle – Weed plant stages

Male, female or hermie? Determine the sex of your plant

It’s important to know if your plants are male, female or hermaphrodites. Above all, if you are growing with the intention of harvesting Marijuana buds, you should only allow female plants to grow. So it’s a good idea to kill the males and hermies ASAP. Male and hermaphrodite plants soon start to pollinate the female plants. You’ll end up with lots of seeds and very few buds.

Male preflowers develop first and very fast! Once those pollen sacs are open, they are bound to start pollinating, not only your crop but most plants 5 km around.

Look for early signs of male plants: they are usually taller and less bushy than female plants. Just eradicate them, unless you want to produce seeds in a controlled environment.

Cannabis plants growing outdoors (soil in pots) – Vegetative stage week by week

Cannabis in vegetative stage - week 1
Cannabis in vegetative stage - week 2
Cannabis in vegetative stage - week 3
Cannabis in vegetative stage - week 4
Cannabis in vegetative stage - week 5
Cannabis in vegetative stage - week 6
Cannabis in vegetative stage - week 7
Cannabis in vegetative stage - week 8

How to tell if your plant is male or female before flowering

Basic growing requirements

Pot size

The size of your plants will be determined by the environment size, growing lights, pot size and the nutrition plan you apply to your crop. The bigger the environment and the more space the roots get in their growing medium. In other words, the taller and more vigorous your plants will be.


Cannabis plants in the vegetative stage thrive in temperatures around 22 – 26°C. Therefore, temperatures below this range may affect negatively the plant, or even kill it if it’s exposed to freezing temperatures for a long period. In addition, high temperatures also affect the plant negatively. Beyond 30°C, the plant may experience burns in the leaves, heat stress and other complications.


Relative humidity measures how much humidity is present in the air expressed as a percentage. In the vegetative stage, the plant grows better in an environment where the RH is around  40-60%.


The main fertilizers that the Cannabis plant needs to develop are Nitrogen (N), Phosphorus (P) and Potassium (K). 

N is key during the vegetative growth, with lower levels of P and K. When the plant starts to bloom, the concentrations of P and K must be increased progressively, while the N concentrations are lowered. That is why there are specific fertilizers for vegetative growth and flowering. 

Other secondary nutrients will be necessary for the correct development of the plant. These are Magnesium (Mg), Calcium (Ca) and Sulfur (S). Finally, the micronutrients are necessary but in a minimum concentration. These are Zinc (Zn), Manganese (Mn), Iron, (Fe), Boron (B), Chlorine (Cl), Cobalt (Co), Copper (Cu), Molybdenum (Mb) and Silicon (Si). 

Several brands of fertilizers offer fertilizer kits specially formulated for each stage with the necessary nutrients. Start with the dose indicated by the manufacturer or even 1/2 lower to avoid saturation and gradually increase the amounts until the desired results are achieved.


Water your plant regularly with clean, safe and water. Certainly, using chlorine-free or filtered water leads to better results. Always avoid overwatering and watch for good drainage. There are a few rules to know if your plants need watering, for example: the first 3 cm of the soil is dry, your plants are wilting, the pot feels too light.

pH levels

In soil mixes, keep the pH levels between 6 and 7 for optimal plant growth. Almost every nutrient is only available for the plant to uptake within this range of pH.


During the vegetative stage, a Cannabis plant growing indoors needs 18 hours of light and 6 hours of darkness a day. The vegetative stage may last for as long as you want in indoor crops. Your plant will continue to grow in size and won’t flower until you change the photoperiod. It depends on the desired final size of the plant for how long to vegetate your plant.

Plan and track all these requirement values and set stage dates in the Grow with Jane app!

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Outdoors, Cannabis plants sprout in Spring and grow in the vegetative stage during Spring and Summer, when they start blooming. When Autumn is coming and the days start to grow shorter, female Cannabis plants stop growing in size. Instead, they develop fat, resinous buds in an attempt to be pollinated by the male plants’ pollen. Look for the first signs of flowering stage outdoors and start counting the flowering days.

Indoors, you just need to change the photoperiod (the hours of light/dark) to a schedule of 12 hours of light and 12 hours of darkness. As a result, this change will trigger the flowering response in the plants. In the next weeks, they will grow in size rapidly and start producing buds. Until then, a plant in the vegetative stage will grow stems and leaves, it may show pre-flowers to indicate sex but the buds won’t get fat.

The next stage of growth in Cannabis plants is the flowering stage. This starts with the already mentioned change of photoperiod. By now, your plants had already grown their bodies strong and have many fan leaves and stems. Those nodes sites with white hair will start growing more and more pistils (hair). After that, it will start to form the buds a.k.a. your future harvest! Keep on working on them!!

First signs of flowering stage in Cannabis plants

28 thoughts on “Vegetative stage in Cannabis plants: a guide for beginners”

    • Hello Jeff! There are many types of LED panels, always look for the manufacturer’s instructions or advice to use your lights to their full potential. For most LED panels, you can have both switches on during flowering, so don’t switch off the veg spectrum, just switch on Flowering as well when you change the photoperiod to 12/12 or when you start seeing preflowers in autos.
      I hope this helps, happy growing!

    • Hi Stuart! For the vegetative stage set your timer to 18 hours of light and 6 hours of darkness. With a 12/12 schedule, photoperiod (regular) Cannabis plants would start flowering and autoflowering plants would be lacking valuable hours of light, which may result in slower growth and smaller plant size.
      Thanks for commenting and happy growing!

    • Hi Dean! Thank you so much for your kind words! I hope you enjoy our articles, specially crafted for beginner growers. Learning step by step is the best way to become an experienced grower sooner than later.
      Happy growing!

  1. Great job on the app, and app design. It would help home/outdoor growers for strains’ data to automatically feed diaries on vegetative/flowering stages and estimated harvesting times.

    • Hi JP, we’re back! When the Marijuana seed opens, the first pair of small round leaves that appear are called “cotyledons”. After that, the little Cannabis plant starts producing leaves with serrated borders. When the true Cannabis hand-shaped leaves appear, the plant enters the vegetative stage. This may take from a couple of days up to 2/3 weeks in some cases.
      Here’s more information about the seedling stage and how to transition between stages.
      Thanks for commenting, have a nice day!

  2. Just found you guys, will definitely check out the app and recommend to new growers. It’s the simplicity of it. Great job and I have to say how awesome it is the way you respond to the questions in comments.

    • Hi Ray! Thank you so much for reading and commenting! We hope you enjoy our blog articles and the growing app as well. As a member of the app, you get access to our Community to share questions and Growlogs with other growers and also email personalized advice and answers to your questions on growing Cannabis. All for free!
      Have a nice day and happy growing!

  3. It’s really helpful and informative, Amazing work…
    The way of explanation and pictures presentation is attractive.
    It cleared many of my doubts while blogging.

    • Hi Pauline, after week 1 or at the end of the seedling stage, week 1 of veg, you can start fertilizing according to the manufacturer’s indications. If you need further help, you can download our app and send us a message. We’ll be happy to take a look at what you have and give you some advice.
      Thanks for reading and commenting! Happy growing!

  4. Good afternoon, I’m taking on the challenge of growing our own Cannabis plants for the first time & your web site outlining the various steps to ultimately reach a healthy plant is very helpful. However, I’m confused when it comes to the lighting schedule during the vegetative stage. Do I start with a 18/6 schedule & eventually change to a 12/12 schedule to promote flowering & if so when do I make the change?

  5. My plants are both 12 wks old and are rather small and can’t tell if they are female. They are about a foot tall and have been topped. When should I change to 12/12?

    • Hi Dan! After 12 weeks you can change to 12/12 whenever you want, you can also give them more time in the veg stage to allow them to grow in size. Take into account that when you change to 12/12 your plants will grow a bit more in size for 1 week or 2 and then will start budding. You can share pics with us and we’ll be happy to tell you if they are male or female. To share your pics with us, please download our free growing app at and send us an in-app message.
      thanks for reading and commenting!


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