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Cannabis Vegetative Stage Guide

Curious how to take care of your plant during the cannabis vegetative stage? Check this blog to avoid common mistakes! Last updated 06/12/2022

    During the cannabis vegetative stage, young seedlings turn into plants which are ready to support the formations of buds. We love watching the development of fragile seedlings turning into robust and healthy specimens which are full of potential - there is nothing more heartwarming for a connoisseur of weed. To make the most out of the vegetative or growth phase, it pays to know as much as possible, so read our guide to help you develop the best practices for your plants.

    The start of the growth phase begins with germinated seeds that point out of the ground and burst into very small green plants. They are very fragile at this stage and need to be carefully protected and watered with care. We will now talk about the growth of these young plants. Growth is a very important factor as it determines the size of the crop and from a cultivation point of view is in many ways more important than flowering itself.

    How long does the vegetative phase last?

    The length of the vegetative phase varies considerably from strain to strain and the method of growing from three to sixteen weeks.

    The importance of the growth period

    The growing season is the time when you can determine the size, shape and harvest of your plants. There are different ways to grow cannabis and they vary greatly depending on how they grow. You can put many plants in a square metre, and then it is important not to leave them for too long in the growth phase. Plants may not be allowed to grow too large or they will destroy each other. If you reduce the number of plants, you can let them grow as they see fit.

    Clones and plants from seeds have different ways of growing. Clones are genetically older plants so they are technically already adults when they are placed in the soil and therefore need a shorter growth period before flowering. A plant emerging from a seed goes through different stages and becomes mature after about a month of growth. If you are a good grower, you will bring your plant to adulthood faster. It is not only a question of time but also of volume. If you look at a clone, you will see that the side branches go through several stages. If you look at an immature young plant, the side branches grow directly. When the plant is mature, the lateral branches will also start to grow in stages.

    You can determine the dimensions of your plants by increasing or reducing the growth time. But remember that a bigger plant does not necessarily mean that you will have a bigger harvest. It is important to know, especially for beginners, that the plant still grows considerably when it is placed in the flowering phase and that it continues for another three weeks before reaching its maximum size.

    Potting up in larger containers

    One of the first things to do when your seedlings are ready, is to carefully place them in larger containers which have enough room for the root system to grow and the foliage to be supported. 

    Different types of growing mediums

    The different substrate can affect the growth rate of your plants. The better quality is, the better the weed. The most commonly used mediums, each with its own characteristics, advantages and disadvantages, are:

    • Soil
    • Coconut
    • Hydro (cultivation in water). 


    Soil only allows rapid growth if it is well ventilated and if its structure is light. Roots grow best in airy, light soil, and that's what we need to provide. The more the roots grow and spread, the more the plant above can grow. The roots need oxygen and a hard, compact soil contains less oxygen than a lighter mixture. The advantage of soil is that it contains nutrients and you don't need to add liquid fertilizer to get started. This can be important for novice growers and save them from early-stage problems and a bad start can be disastrous for future flowering and harvesting. The earth is thus a perfect substrate for beginners who, starting out in this way, can gain experience. Learning to cultivate well in the soil allows you to come back to it any time later.


    Coconut is a more airy material and has become a favourite substrate of many professional growers. It provides plants with a good start thanks to its oxygen-rich coconut fibres. Plants growing in an oxygen-rich environment are stronger and develop more - and more solidly - lateral branches. The downside with coconut is that it doesn't contain any nutrients. That’s why you need to start early with liquid fertilizer. This can cause problems but the coconut is easy to use and it is difficult to over-fertilize it. It’s maybe even more difficult than with soil.


    The fastest growth rate is frequently seen with hydroponics setups, as long as they are maintained correctly because the roots have easy access to all the oxygen they need. However, this requires more effort than growing in the ground or in coconut fibre. Coconut offers a happy medium between earth and hydro and delivers good growth results without demanding too much attention. It must be said that once you master growing hydro weed, it is very impressive. The only disadvantage is the fact that you are more dependent on electrical devices and if they mess up or there is a power outage, there are serious problems.

    How much water should I give plants during the growth phase?

    Cannabis plants need more water as they begin the vegetative phase, so make sure that the soil does not dry out. At the start of the phase, pour water close to the stem, but as the plant grows its root system spreads underground so you will need to water further away from the stem. This will encourage the roots to spread out even further and use the soil more efficiently. The exact amount of water depends on the temperature, humidity and many other variables so it is best to watch for the signs that your plants are thirsty or satisfied.

    Lightning during the vegetative stage

    Putting a plant in pre-growth means keeping the plant in its growth period (also known as vegetative) for a period ranging from one day to several weeks. We do this by setting the lamps to a cycle of 18:6 - which means 18 hours of daylight and 6 hours of darkness for the plants. The plant is equipped to receive the full benefits of light and begins to grow in width and height.

    Giving your plants the best start in life

    Most growers use root stimulants for powerful growth. As has been the case so far, everything that happens here takes place in the ground, to begin with. A plantule has only a few roots so root stimulants aim to encourage the plant to produce as many roots as possible as quickly as possible. These are most commonly in liquid form and all the main producers of fertilizers have their own version. These stimulants ensure that the roots receive a growth impulse and work best in soil. These stimulants will also encourage the growth of other plants present in your soil. Don't be afraid if you see all kinds of little green spikes popping out of the ground - just pull them up when you notice them.

    These root stimulants are usually diluted with water but are used neat to soak the cuttings to encourage them to develop roots when making clones. Root stimulants are not used at the same time as liquid fertilizer as this reduces the effects of the stimulants. Thus, during the first days of a plant, it should be given root stimulants - and not mixed with other fertilizers to give it the best start in life.

    Optimal growth

    What is the perfect growth for weed plants? Perfect growth is when the plant has reached its ideal size before starting to flower and when plants can continue to grow without jostling each other. The grow tent is completely filled with plants with no free space between them but not enough for the plants to compete for resources. By letting them grow large or by cramming too many plants into a small space, all the plants will develop less well. A plant needs space for its side branches. Otherwise, it will grow in height and the side branches will be weak and will not bear beautiful kolas.

    To obtain a good harvest, it is necessary to allow good development of the heads on the lower branches as at the top. Anyone can grow a nice big central head, but it’s a completely different story when it comes to having the same weight on the lowest branches. However, that’s how you get a good harvest from just a few plants.

    Nutrients during the vegetative phase

    During the growth period, the plant mainly needs nitrogen and potassium. If the plant lacks one of these two elements during its growth, the leaves will turn yellow. If you choose to cultivate in soil, use a good mixture available in the grow shops that contain these elements enough for three weeks to a month. This has the advantage of not requiring additional fertilizers until flowering. The slightly higher price for better quality is worth it and you will save yourself potential problems. An inexpensive soil mixture can lead to deficiencies because there are insufficient plant nutrients. It is then necessary to add liquid fertilizers which is not a problem in itself except for people who tend to overdose. It's always best to wait for a while before adding more.

    The dangers of overfeeding

    Overfeeding comes from the accumulation of minerals that are present in all fertilizers. Over time, if you use too high doses of nutrients (because you are just starting), plants can no longer absorb them quickly enough. Spots appear on the leaves, especially at the edges where they widen, then the leaves dry out and die. To avoid this, you can rinse the substrate - something that you will need to do again in the week before harvest. Rinsing means adding an amount of water which will dilute the salts and flush them out. If your plant has deep green leaves, this is a sign that there is enough fertilizer and adding more will cause overfeeding. If you are not sure, wait until the leaves clear up a bit. You will know when the plants are hungry. If you wait too long, the leaves will turn yellow.

    However, mistakes cannot be avoided when growing cannabis. In fact, the more you do, the better. Learning from mistakes is the best way of learning what works and what doesn't. Always follow the instructions on the bottle and use a millimetre syringe to measure the exact amount you want to add to the water. A good dosage, without excess, will produce superb plants in great shape.

    The bigger the plant, the more fertilizer it needs. You can notice that if you keep giving the same concentration of nutrients to the plants, the leaves will start to turn yellow at some point.

    Over time, you will notice that the cannabis plants begin to grow faster and faster as they head towards the end of the growth stage.

    During the growth period, there is little else to do than add root stimulant and liquid fertilizer. Lights should be generally about 30-40cm above the plant. Just place your hand under the lamp at the height of the plants to measure the heat it gives off. The correct distance varies depending on the size of the lamps in it. If there is good air circulation, the lights can hang a little lower because the hot air is immediately replaced in the surroundings of the plants and this causes them less stress.

    Humidity and temperature during the growth phase

    The humidity of the air should be kept as high as possible during the first weeks so that the plants can grow faster and the leaves come out more easily. High humidity in the air can work wonders and can be done by reducing air extraction. A humidifier can be very useful too! The temperature should be between 22 and 28 degrees Celsius during the day and between 18 and 22 degrees at night. The temperature should not drop below 16 degrees because growth would decrease or even stall.

    The green plants have now grown, you can pet the vigorous stems and enjoy the taste and smell of your next harvest. It takes a few more months of patience before you can enjoy the heavy buds that will be harvested.

    If you would like to grow cannabis successfully, it is essential to learn as much as you can about its life cycle. You can read more about the other stages at Weedseedsexpress as well as an extensive selection of the finest cannabis seeds in the world.