The Cannabis plant has two main stages in its life cycle: vegetative and flowering stage. 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 seedlings and come back later!

Full article: How to avoid stunted growth in the Seedling stage

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 the vegetative stage take 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.

Full article: The Cannabis plant life cycle (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 little buds.

As said before, only female plants produce buds, male and hermaphrodite won’t do it!

Full article: Identify the sex of your Cannabis plant

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

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.

Temperature

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.

Humidity

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%.

Nutrients

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.

Watering

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

Keep the pH levels between 6.5 and 7 for optimal plant growth. Almost every nutrient is only available for the plant to uptake within this range of pH.

Light

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.

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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.

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!!