What Should You Know About the Vegetative Stage?

Everything about the cannabis vegetative stage
December 28, 2020

The vegetative stage is when your marijuana plants gain mass, develop branches, stems, and leaves. Hence, providing the perfect conditions to lay the foundation for their health and vitality is of utmost importance.

You can do that once you have a thorough understanding of their needs during this period. All you need to realize is that by taking care of them, the reward comes in the form of a bountiful harvest of potent, aromatic buds.

Do you want to know more about how to care for your plants during the vegetative period?

Let’s dive right into it.

What is the Vegetative Stage?

This growth phase is the period between germination and before flowering. It can last from a few weeks to several months, ending when the plants start to produce buds. The production of flowers happens when plants reach full maturity or are triggered by atmospheric conditions.

A Quick Recap of the Different Stages of Growth

Plants, like all living things, go through different stages during their life cycle. The ultimate goal is to reproduce before the end of their life. All plants grow to make copies of themselves from birth to death, ensuring that their species live after they are gone.

The life cycle of cannabis is similar to any other plant. It goes through the following stages:

  • Seed. Hidden beneath inside is a tiny embryo. There is enough food to keep it in a state of suspended animation within the seed’s hull until it is ready to break out.
  • Germination. Once exposed to the right amounts of water, heat, and light, the embryo wakes up. The seed’s hull splits open, and the radicle (what later becomes the primary root) pokes through. It is now a sprout.
  • Seedling. The first round-edged leaves of the plant begin to emerge and grow for about 2-3 weeks. At this stage, it is highly vulnerable to disease and mold.
  • Vegetative. The baby plant starts to produce more leaves with the familiar shape of the blades. It is now in the teenage period. For the next 3 to 16 weeks (depending on the strain), the stems and roots become thicker and more robust.
  • Flowering. During this stage, the plant stops “growing” and focuses its energy on producing flowers. For 7 to 12 weeks (depending on the strain), the buds develop and mature. Pretty soon, it will be time to harvest.

It is also possible to use cuttings from a living plant and skip the first stages. Horticulturists call this process “vegetative propagation.” We know it only as “cloning.”

What Happens During this Stage?

So much has been said about the importance of the marijuana vegetative stage. And yes, how you care for the plants during this period would have far-reaching implications during the flowering period and beyond. During this time, what can you expect?

Leaves, Stems, and Roots

A seedling starts with two cotyledons. These oval-shaped primordial leaves are the energy source for the initial growth of the plants. Over the next 2-3 weeks, the seedlings mature and produce more fan leaves. They are the “true” leaves that facilitate photosynthesis.

When a seedling has produced at least seven sets of “true leaves” and an 8th set is about to emerge from the tip, you know that it has entered the veg stage. You will also notice the stem developing a thicker skin and hardening off. Gradually, the primary stem rises, and spaces between nodes increase.

Another sign is the maturing of the root system. While the above-ground parts of the plants are hardening off, they are much more active underneath. The roots are growing downward and outwards to absorb as many nutrients as they can from the soil. Generally, there is three times more root mass than what you see above the soil line.

All these new and rapidly changing parts allow the plants to maximize the photosynthetic process. During this period, they stockpile water and nutrients while getting ready for the next stage – reproduction. Their gender also starts to manifest before flowering.

Duration and Timing

The veg stage (also known as the “growth stage”) can last between 3 to 16 weeks. As for the actual duration, that would depend on the specific strain and your intentions. As long as the plants are only producing leaves and stems, and no buds, they remain in the vegetative stage.

For outdoor growers, the plant’s vegetative period starts in late spring/early summer. The transition from summer to autumn naturally ends it. You can do nothing to control the timing because your plant will be taking its signals from the sun.

On the other hand, growing indoors lets you supply as much light as they want. You can keep the plants in the veg stage for as long as you want by giving them 18 hours of light exposure a day. They would not be producing buds, no until you shorten the daylight hours to 12. That means you have the choice of triggering the transition to flowering earlier or later.

The Importance of the Vegetative Stage

The vegetative stage is a crucial period in the life cycle of cannabis plants. You have to provide the best environment for your plants to grow as big and healthy as possible. That is because plant size is usually a good indicator of yield. The larger your plants are, the more nodes (or bud sites) they will develop.

However, size is not the only objective. It is possible to achieve an excellent yield even with a small but adequately trained plant. Ideally, you should start during the veg stage, before the first flowers emerge.

This growth phase is when critical biological processes are happening. The leaves are busy with photosynthesis, converting light, water, and carbon dioxide into food. The roots not only gather water and nutrients but also keep the plant firmly anchored.

Because the plants grow like a weed (pun intended), they need adequate amounts of light, moisture, and nutrients. Not having enough resources will stunt its growth, and they would not reach their full potential.

You should also be aware of pests and pathogens during this time. Early prevention of these threats will prevent disappointment in the later stages of plant development.

Caring for Your Plants During the Vegetative Stage

The different growth stages are interconnected and dependent on one another. A healthy seedling phase helps boost a robust vegetative growth, which contributes to a bountiful flowering period.

Let us look at the critical factors that will determine the fate of your plants.

Growing Medium

You can raise plants using different media. For soil substrates, ensure that you have enough space and the correct amount of water and nutrients. Consider supplementing with organic fertilizer and beneficial microorganisms like fungi.

If you are using a hydroponic system, use filtered good-quality water. Avoid using tap water because the added chlorine and minerals could harm your plant.


Transpiration is the process in which water moves up the stem of the plant to the leaves. This movement creates a suction-like effect to absorb nutrients, bringing them to where they are needed.

You should increase watering frequency as the plants grow. Initially, the young plants would need water near the central stalk. As they grow in size, the roots expand outward, so you should also water further out from the center. This way, the roots can absorb water more efficiently.

But take care, because too much water can also be harmful.

Overwatering can decrease the air around the roots and could lead to root rot. Whenever you water your plants during the vegetative phase, it is better to wait for the top inch (3cm) of soil to dry out before watering again.

Hydroponic plants get all the water they need from the nutrient solution. Closely monitor the pH level and keep it between 6.0 and 6.5. Too low (acidic) or too high (basic) will affect the roots’ ability to absorb nutrients.


Your plants have particular nutritional requirements which will differ during the different growing stages. In the vegetative period, they are especially in need of higher levels of nitrogen.

Nitrogen plays a crucial role in the production of new cells and enzymes. Plants need it to produce chlorophyll, which allows them to absorb energy from light. It is also a significant contributor to the growth of stems and leaves.

Another nutrient your plants need is potassium. This mineral promotes the uptake of water from the roots and regulates the rate of photosynthesis. It is also essential for the development of flowers as well as fighting diseases.

During the vegetative period, phosphorus encourages root growth. It is also involved in the formation of sugars, starches, and oils. Phosphorus is one of the primary components of a plant’s genetic material. The other essential nutrients are magnesium (the building block of chlorophyll) and calcium (which strengthens cell walls).

Keep in mind that nitrogen is the most vital nutrient during the veg stage. When the plant transitions to flowering, switch to a higher phosphorus and potassium mix. Excess nitrogen can, in this phase, actually inhibit the development of flowers.

You can buy micro-nutrient formulas to make things simple. FoxFarm is one of the better brands, and they have several products you could choose from for vegging plants.


Light is an essential aspect to consider when growing cannabis. As mentioned, it is the catalyst for photosynthesis, together with water and CO2.

Outdoor plants are dependent on the sun’s cycles. Cannabis naturally goes into the veg stage in late spring or early summer because of the longer daylight hours. Hopefully, your plants will get all the sun they need during the summer months. On days when the weather does not cooperate, you can’t do anything about it.

Indoor cultivators have a lot more control. A good set of grow lights will help your plants grow healthy and strong. HID lights (MH + HPS) produce the most buds per watt, although LEDs are becoming popular because they are energy efficient. They also do not emit as much heat.

During the vegetative phase, we usually employ an 18-hour photoperiod (“daytime”). Plants grow faster when they receive more light, and you can shorten the veg stage and hasten flowering if you wish. But it is better to keep your plants from budding for 4-8 weeks to give them time to develop a sturdier root system.

To initiate the flowering stage, change your light schedule to 12 hours on/12 hours off. The plant will think that summer is over, and it is time to reproduce before winter comes.

Plants grown from autoflowering seeds will transition to budding by themselves, according to their schedule. You can keep the lights on up to 24 hours a day. However, there is some debate about whether this is beneficial. Some cultivators believe alternating light and dark, warm and cool temp, are required for optimum health. Others say that the gains from the final product do not justify the added cost of electricity.

Because the plants quickly grow during the veg stage, you must continuously adjust the lights’ height and the plants’ position. The light source should be at least 1 foot (30cm) away from the upper canopy. If it is too close, they could get a light burn. If you notice the leaves turning yellow, you should move the plant even further away.

Temperature and Humidity

For the vegetative stage, maintain a temperature range of 70-78°F (21-26°C). As much as possible, do not let the temp dip to lower than 10-15° during nighttime.

In the first week of vegetation, keep the humidity level at 60-80%. Higher moisture content in the air allows the plant to absorb water directly through its leaves while transitioning from the seedling stage.

Afterward, lower the relative humidity by 5% every week until it reaches 45-55%. If you notice wet spots on the leaves, that tells you the moisture level is still too high.

You can measure the temperature and relative humidity by using a thermometer/hygrometer combo meter. Try to get a device with a long probe so that you can check the atmospheric conditions from outside the grow room.

You can use heaters, air-conditioners, evaporative coolers to control the indoor temperature if the usual measures are not enough. And if needed, you can use humidifiers and dehumidifiers to manipulate the moisture level. Just remember to avoid too hot or too cold spots inside the room. Fans will help you to equalize the temperature by pushing the air around.

Outdoors, it may be necessary to invest in shades to protect your garden from the elements. Cannabis plants have adapted to thrive in a broad range of conditions. However, you still want to watch out for unexpected heatwaves or sudden downpours.


Good air movement is essential to keep your plants healthy. Keep the air inside your grow room or tent fresh by installing fans. An extractor fan is particularly useful because it provides ventilation and reduces condensation, thus preventing mold formation. It will also draw in carbon dioxide and remove excess oxygen to keep the photosynthetic process at an optimum level.

If you are growing outdoors, you want to see the leaves rustling – a sign of adequate airflow. However, if your area is prone to high winds, you should install a wind shelter. Strong gusts could topple your plants, especially in the early stages of root development, or when the plants are heavy with buds.

Spacing and Training

Every plant needs adequate space to stretch out and grow. Crowding blocks out the light and causes unnecessary competition for water and nutrients. But how much space is enough? It depends on the marijuana strain you are growing.

Indica strains usually do not grow too tall, and instead expand more laterally, while Sativa strains tend to grow taller. Autoflowering plants are relatively shorter, with some reaching a maximum of 20 inches (50cm). Whatever marijuana strain you choose, it is possible to train your plants to fit in the available space.

Training lets you shape plants to the size and contour wanted by bending or tying down the branches. You could even boost yield while keeping the plants at a height that is more convenient for you. Depending on the training technique used, you can place 4 to 16 plants per 10 square feet (1 sqm).

Other Considerations During the Vegetative Stage

Apart from providing primary care, you would also want to be aware of and do a few other things. These would include knowing when and how to move the plants to their final containers, identifying their genders, and manipulating their structure.

Transplanting Seedlings

When the stems harden in the late seedling stage, and you see roots poking out from the bottom of their containers, they enter the vegetative stage. It is time to transplant them to a bigger pot or into the ground. Be careful, as undue stress could stunt their growth. Do not tear or cut the roots.

To begin transplanting, invert a seedling cup into your hand’s palm and gently tap on its bottom. Catch the little plant and the potting mix in your hand, then carefully place them into the hole that you have prepared. Keep the base of the stalk at the same level as the top of the new soil. Water it so that the roots can settle in, and if it is indoors, check the temperature and lighting.

It is not unusual for a young plant to undergo “transplant shock” for a day or two, but try to keep this at a minimum by disturbing it as little as possible. Preferably, transplant as early as possible, so that there are fewer disruptions in the later stages.

The size of the container depends on your height and width objectives for the plants. Most of the growth will indeed occur in the veg stage, but be aware that your plants will experience one last growth spurt at the start of the flowering stage.

During this final stretch, some strains could double in size. With a bit of foresight, it would not be necessary to transplant more than once (or maximum twice) in a lifetime.


During the late vegetative period, your plants will show their sex. Determining their gender is vital because mixing males and females in the same growing space could be disastrous. When male pollen fertilizes female flowers, they will start to produce seeds. You can say goodbye to the resinous buds that are your ultimate goal.

Towards the middle until the end of vegetation, examine the 5th series of leaves on your plant. Both sexes will begin producing pre-flowers, and you would tell which is which by the shape. Males will create a small sphere, while female genitalia will look like tiny fibers or tendrils.

Any make plant you found must be banished from the grow space. You can save them for breeding, or just get rid of them to avoid pollinating your precious females.


A popular method of controlling the height of marijuana plants while boosting their yield is topping. Whereas training is bending or tying stems and branches to achieve the desired shape and size, topping involves cutting and trimming. Use sterilized scissors to cut the apex of the primary stalk.

That causes it to diverge and grow laterally instead of straight up. This technique increases the number of bud sites.

Employ this technique during the vegetative period, as soon as the plant has 3-5 nodes. You can repeat the process as many times as you want, but the plant will need a recovery period every time you top. That will make the veg phase longer and delay the onset of the flowering stage.

Keep your Plants Happy During the Vegetative Stage

During the veg stage, your marijuana plant will produce the leaves, stems, and roots to support it throughout its life until the flowering stage. Give it the right amounts of light, water, and nutrients to grow big and strong. The proper temperature, humidity, and airflow also play critical roles in the plant’s health.

Growers should consider that transplanting, training, topping, and determining the sex of the plants are all done during this period. Learn the proper techniques and avoid disappointments later.

The vegetative period is when you will see the bulk of the growth of your plants. Keep them in optimum health, and you will be more than satisfied when harvest time comes.