The vegetative stage of weed: A ‘no-fail’ grow guide

Having put down its roots and survived the seedling stage, your plant is now transitioning into full vegetative growth. The vegetative stage of cannabis is a crucial period in the plant’s life cycle. During this time, your plants will transform from a delicate sprout into a robust and thriving plant that is ready to pack on heaps of bud. You should think of the vegetative stage as the period where your plant builds a solid foundation of thick stems and branches with a dense foliage. Come flowering time and your plant will be ready to absorb plenty of the suns energy and the solid branches it has formed will hold those dense heavy buds without a problem.

What is the vegetative stage of cannabis plants?

The vegetative stage of a cannabis plant is the main period of growth where the plant puts all of its energy into developing leaves, stems, and roots. During this time, the plant focuses on building its basic structure, with leaves unfurling to soak up sunlight and roots reaching deep into the soil to absorb essential nutrients. With each passing day, the plant becomes stronger and more resilient, laying foundation for the flowering stage.

The veg stage is a critical moment in a plant’s life cycle, and it is incredibly important that it has optimal growing conditions that allow it to produce a large and robust structure before the flowering stage. Adequate light, water, and nutrients will encourage the development of a strong and healthy cannabis plant that is capable of producing lots of dense bud.

How long does a weed plant stay in vegetative stage?

In the natural environment, as the seasons change and the days grow shorter, the daylight hours available to the cannabis plant reduce and this triggers a signal in the plant that it is time to move into the flowering phase. The vegetative stage will end when the plant receives less than 12-13 hours of light per day. This causes the plant to transition into the flowering stage where it stops growing taller and starts to produce bud.

Cannabis is an annual plant, which means in the wild it will die out in winter (in colder regions). In the wild cannabis automatically switches to the flowering stage according to light, hence the name ‘photoperiod’. This is a natural survival mechanism that allows the female plant to produce its offspring that will carry on its genetics after it dies. The way that this works is a female flower becomes pollinated by a male plant, the female begins producing seeds which fill the flowers. Come winter as the flowers fall to the ground, carrying its seeds, they soak into the cold soil and as temperatures warm, they begin to germinate in time for spring.

Understanding how light pattern affects cannabis phases of life helps growers to plan for their crops:

• If grown outdoors, weed plants stay in vegetative stage until late summer or early fall. In the Northern Hemisphere, this is around September or October. That being said, the exact timing of the end of the vegetative stage still depends on various factors, such as the specific strain being grown, the local climate, and growing conditions.
• If grown indoors, weed plants stay in vegetative stage until you want it to switch to flowering, since you have total control of its light schedule.
• The only exception to these rules are autoflowering plants. Autoflowering cannabis strains are genetically programmed to flower after a set period of time, usually 3-5 weeks, regardless of light cycles.

How long is the vegetative stage length when growing indoors?

The length of cannabis vegetative stage is a choice for indoors growers. Having total control of the growing conditions mean you can decide when the weed veg stage ends and switch the plant to flowering stage, simply by manipulating its light cycle (unless it is autoflowering or it is grown outside).

If you are growing indoors the length of the veg stage is your choice, the longer you veg for the bigger your plants will grow, and the more they will yield. The average growers veg stage can last anywhere from 2 -16 weeks depending on the strain. Here is a rough guide to how long you should be vegging for:

• Regular or feminized indica – Veg stage should last from 6 – 12 weeks but can go on longer.
• Regular or feminized sativa – Veg stage should last from 5 – 10 weeks but can go on longer.
• Autoflower – Veg stage lasts for 2 – 4 weeks before the plant automatically flowers.

As mentioned above, autoflowering strains do not require you to change the light schedule to initiate flowering. Therefore, autoflowering strains are a popular choice for indoor and outdoor growers who want a quick and straightforward growing process.

When should I switch from vegetative stage to flowering?

The choice is yours if your grow is indoors. But before you decide, remember though, that the length of this stage will ultimately impact the overall size and yield of your cannabis plants, so it’s important to consider this if you want to achieve big yields.

You can safely switch to flowering stage when your cannabis plants have reached a desired size and have developed sufficient branching. This usually occurs after 4-8 weeks of vegetative growth, but it can vary based on the specific strain and growing conditions.

Is 4 week veg enough?

4 weeks typically is the minimum for weed veg stage; although it is best to keep your plants in the vegetative stage for longer than this to allow for more substantial growth and branching. Remember if your plant is still small with thin branches it wont be able to hold much bud when it begins flowering so yields will be much smaller. On occasion the buds can also grow too heavy for a plant that has not had enough time to strengthen causing the branches to snap. This can result in smaller yields and underripe low potency bud.

How big should my plants be after 4 weeks?

On average, a cannabis plant grown from seed can reach a height of 8-18 inches (20-45 cm) after 4 weeks grown from seeds, but this can vary greatly depending on many factors including its type of weed strain (Sativa/ Indica/ Hybrid or autoflower), its growing conditions, and whether it is grown indoors or outdoors.

Below are pictures of 2 cannabis plants of at 4 week-old, you can see they are quite different in size.

What if I grow my cannabis plants outdoors? When should I plant cannabis outdoors to ensure a decent vegetative stage?

The perfect time to plant weed outdoors depends on your location and climate. However, there are a few guidelines you can follow to ensure that your plants have a long enough vegetative stage before they enter the flowering stage.

Timing: Cannabis plants like warm weather and so it is best to make sure the daytime temperatures are consistently between 65°F – 85°F (18°C – 29°C). This is typically in late spring or early summer, but the exact timing will depend on your location.

Light: Cannabis plants need a lot of light during the vegetative stage in order to photosynthesize and grow healthy and strong. If you are planting outdoors, make sure that your plants receive a minimum of 8-12 hours of direct sunlight per day. Avoid planting them in heavily shaded areas and remember a photoperiod needs at least 13-14 hours of daylight to prevent it from entering the flowering phase.

You should time you outdoor grows according to daylight hours and the seasons. An easy way to work out when to begin growing weed outdoors is to count backwards from the end of summer. For example, if you know that you want to veg your plant for 10 weeks, and the daylight dips down to 12 hours per day at the end of September, this is when your plant will begin flowering. Therefore, if you want an 8 week veg, you need to make sure your plant is in the ground at least 10 weeks prior to the end of September. This will allow 2 weeks in the seedling stage, followed by 8 weeks in the vegetative stage before it begins to flower.

Water: It is vital to make sure your plants have plenty of water, especially during hot or dry spells. Make sure you water your plants regularly and thoroughly, especially during the middle of summer. Be sure to water them in the evenings only! Watering during the morning on a hot summer day can cause the leaves to burn if they get wet. Alternatively if you do have to water during the daytime, make sure you only water the soil and not the leaves of the plants.

Protection: Finally, it’s important to provide your outdoor cannabis plants with some protection from the elements, such as wind, rain, and extreme temperatures. A simple hoop house or row cover can help to provide the protection your plants need. This is not essential as plants will grow well outdoors without it, however, it can be useful to prevent pests etc.

By planting cannabis outdoors at the right time and providing the right growing conditions, you can ensure that your plants have a decent vegetative stage before they begin to flower. This will give them a strong foundation and allow a plant to grow plenty of bud.

What is the best light schedule for weed plants during vegetative stage?

The optimal light cycle for weed plants during the vegetative stage when growing indoors varies based on the strain and the growing conditions; but one cycle that has proven to be effective for many growers is 18 hours of light and 6 hours of darkness. This cycle stimulates vegetative growth and encourages the development of strong, healthy plants.

Once the plants reach a desired size, you can adjust the light cycle to 12 hours of light and 12 hours of darkness per day, which triggers the plant to enter the flowering stage and begin producing buds. It’s important to keep in mind that light intensity and spectrum also play a crucial role in plant growth and yield, so adjusting those factors along with the light cycle can help to optimize yields even further.

When to start 18/6 light cycle?

As soon as your seed has germinated, or your clone taking root, it’s time to commence with the 18/6 light cycle.

Many growers use a separate light or setting (if using LED’s) specifically during the seedling stage. This is because young cannabis plants grow best under a blue light spectrum. Blue light has a wavelength range of 400 to 500 nanometers, and it is absorbed well by chlorophyll, which is essential for photosynthesis and plant growth. During the seedling stage, plants do not yet require the red light spectrum, which is necessary for flowering.

Both LED and fluorescent grow lights emit high levels of blue light. Some popular options include T5 fluorescent lights, or LED grow lights specifically designed for the vegetative stage, such as those marketed for use with cannabis.

Can I grow weed with 24 hours of light?

Some advanced growers may experiment with 24 hours of light, but it is not recommended for the majority of the growing cycle. Like most plants, cannabis plants have a natural light cycle that they have evolved to follow, with a period of darkness each day. Cannabis plants like any living thing need a rest and recovery period, this is what the darkness is for. When grown under 24 hours of light it can eventually stress the plant or lead to light burn

Having your grow light on for 24 hours can also use a lot of energy and raise your grow room temperature by quite a bit, causing your plants to wilt and droop. If your cannabis plant is big or bushy enough, drooping can cause the branches to snap, because the stem of the plant will lose strength as it loses water, increasing the chances of it snapping.

There are of course, exceptions. You can grow autoflowers on a 24 hour light cycle since they require no change in light to begin flowering. However, remember that all living things need rest and recovery, so if you plan to grow your autos on a 24 hour light cycle, watch closely for any signs of stress such as drying leaves, drooping branches or discolouration. If any of these signs show up, you should change your light cycle to incorporate a recovery period of darkness of at least 2-4 hours per day.

The other exceptions are strains that have high tolerance to heat and prefer 20-24 hour light cycles. Sativas strains such as Durban Poison or Super Silver Haze  for instance are native to warm climates and can tolerate longer days.

Key things to consider during vegetative stage of weed

The vegetative stage of weed requires you to closely monitor your plants and make any adjustments if you see signs of stress or any kind of issue at all. Here are some key points you need to stay on top of for a successful veg stage….

• Give your cannabis plants the best start possible using a suitable growing medium that offers good drainage, nutrition and water retention.
• Make sure you give your plants plenty of water but don’t over water them.
• Transplant at the right time to give the roots of your plant plenty of room to grow.
• Adjust the nutrients level, pH, temperature, humidity, lighting, and air circulation to provide optimum conditions.
• Keep a eye on the sex of your plants during the late veg stage and get ready to cull any male plants.
• Watch out for nasty pests or disease that could harm your plants.

Improving the growing medium for your cannabis plants

A growing medium is the material used to support the roots of a cannabis plant and provide anchorage, water, air and nutrients. Some common types of growing mediums include soil, coco coir, rockwool, vermiculite, perlite, peat moss. Each type of growing medium has its own unique properties, advantages and disadvantages.

Choosing the right medium for your plants will depend on several factors, including the strain, personal preference and growing methods (think about whether you plan to grow indoors, outdoors, and whether you plant to use hydroponics such as DWC/ aquaponics/ aeroponics system etc). The growing medium plays a critical role in the growth and success of your plants, so it’s important to choose the right one for your needs, as well as to improve it as necessary.

Read our detailed guide on growing medium and the best soil for cannabis for more ideas.

How much water do cannabis plants need during vegetative stage?

Cannabis plants in the vegetative stage are like young saplings, thirsting for water as they grow and mature. Having said that, the amount of water you give them should be proportionate to their roots size. The amount of water that a cannabis plant needs during the vegetative stage can vary based on a number of factors, including the size and age of the plant, the growing conditions, the type of soil or growing medium, and the temperature and humidity levels.

Here are some tips for watering your cannabis plants your cannabis plants during this stage:

• Check soil moisture: Before watering, check the moisture level of the soil by sticking your finger about 2 inches into the soil. If it feels dry, it’s time to water. If it feels moist, it is safer to wait a few more days.
• Use lukewarm water: Use water that is close to room temperature, as cold water can shock the roots and affect plant growth.
• Water deeply: When you do water cannabis plants, water them thoroughly so that the soil is evenly moist. You can also provide water until it starts to run out of the bottom of the container, then allow the plants to drain thoroughly before being returned to the growing area. This will encourage deep root growth, which is important for the overall health of the plant.
• Avoid overwatering: Overwatering can lead to root rot, which is a common problem in cannabis cultivation. To avoid overwatering, be sure to let the soil dry out slightly between waterings.
• Water and monitor regularly: Cannabis plants need a consistent water supply to remain healthy and vigorous during the vegetative stage. Aim to water your plants on a regular schedule, such as every 2-3 days, and adjust as needed depending on the growing conditions and the size of the plants.

A happy balance between moisture and air is key for a thriving cannabis plant.

What are the best nutrients for veg stage?

The primary nutrients that cannabis plants need during the vegetative stage are:

• Nitrogen (N): An essential element for healthy foliage growth, and therefore Nitrogen is the primary macronutrient that cannabis plants need during the vegetative stage.
• Phosphorus (P): Phosphorus plays a key role in the overall health of the plant, and it is essential for root development and flowering.
• Potassium (K): Potassium helps to regulate water balance in the plant and supports strong stems and vigorous growth.
• Calcium (Ca): Calcium is essential for cell division and growth, and it also helps to prevent common problems like blossom end rot.
• Magnesium (Mg): Magnesium is an important component of chlorophyll, and it is also essential for the production of oils and resins in the plant.

In addition to these primary nutrients, cannabis plants also require trace elements like iron, manganese, and zinc, which are important for overall health.

When selecting a fertilizer for your cannabis plants, look for a formula that provides all of these essential nutrients in the right proportions. The right NPK balance is crucial to the success of your crop; and for this stage, a fertilizer with an ratio that is slightly higher in nitrogen (N) such as an NPK ratio of 3-1-2 will help promote lush foliage growth.

You should always follow the manufacturer’s instructions for application rates and schedules, and monitor the nutrient levels in the soil regularly. It will be wise to err on the side of caution when it comes to feeding. Issues stemming from under-fertilization is easier to correct compared to those resulting from lavishing your plant with excessive nutrients.

When should you start using nutrients on cannabis?

As mentioned earlier, somewhere between the third and fourth week, a cannabis plant will have used up all the energy left in the seed so it is a good idea to start feeding it gradually. Read our guide about cannabis nutrients for more details.

You can feed your plants every 1-2 weeks, alternating with plain water to flush out any excess salts. Remember to regularly check the pH level of the nutrient solution to ensure it’s within the optimal range for the plants. With the right balance of nutrients and proper feeding techniques, your cannabis plants will thrive and flourish.

What is the best pH for cannabis in veg?

Cannabis plants have a fondness for soil with a slight hint of acidity. To ensure they flourish and grow to their full potential, it’s best to keep the soil’s pH levels at a range of 5.5 to 6.5. All the essential nutrients that your little green friends need to thrive are only accessible to them within this pH range.

Monitor and correct the pH levels as soon as possible if your pH meter displays an abnormal reading.

When is the best time for cannabis transplanting?

If you are growing autoflowers, it is best to grow them in the final pot from seed and avoid transplanting if possible, unless they become root bound of course.

For photoperiods, it’s always best to transplant them during the vegetative stage before they start to flower. Once they switch to flowering stage, transplanting can cause root damage, shock, and a decrease in energy and resources, leading to a reduction in yield and potency.

Transplanting should not be done at the germination stage as it will traumatize your young plant and result in a setback of growth by a week or more.

Cannabis plants can endure more 2-3 transplants over their life without it being too disruptive but it all comes down to the ultimate size you want your plants to be. These are the safest time to transplant:

• Where your weed plant has sprouted 4-5 sets of leaves. This is typically between week 4-8, depending on their strain.
• When it has outgrown its current container. If this happens, you will see its roots growing out of the drainage holes of the container.
• When you decide to end its vegetative stage and switch to flowering stage. Make sure that 2-3 weeks before flowering, your plant is in its final pot or in the ground.

What is the best temperature and humidity for vegging?

During the veg stage cannabis plants thrive in warmer temperatures that replicate summer, somewhere between 65°F – 85°F (18°C – 29°C). During the ‘day’ (when the light is on), grow room temperature should be kept in the upper range of this scale, while at ‘night’ (light out) you can drop a few degrees down. Temperatures should not fluctuate too much as this can cause stress to the plants.

Cannabis plants at vegetative stage can tolerate high humidity. Relative humidity levels can be kept between 40%-70%, a bit higher than the flowering stage.

For those who choose to grow their cannabis plants indoors, the luxury of controlling the environment is easy with the use of heaters, air conditioning units, humidifiers and dehumidifiers. On the other hand, those who opt for an outdoor grow can create a protected haven for their vegging plants by using a shelter to guard against any harsh weather that comes their way.

Circulate the air

Adequate air flow keeps humidity from getting too high, which can lead to mold and mildew growth. It also helps to ensure that they receive a sufficient supply of carbon dioxide, which is essential for photosynthesis.

Having proper air circulation also helps to strengthen the plants structure. During the flowering period, big yielding strains can often become weighed down by the large buds they produce. As such, introducing a gentle breeze in the grow room will help make the plants to sway and move and instinctively work to withstand the air currents and support the weight of their buds. Over time, this will help strengthen the branches.

There are several ways to circulate the air in your grow space:

• Fans: Using oscillating fans to create a gentle breeze can help to circulate the air and reduce humidity levels. Place fans where they move air around the plants, but not directly on them, to avoid stressing the plants.
• Intake and exhaust vents: Installing intake and exhaust vents in your grow room can help to create a steady flow of fresh air, while also removing stale air.
• Open windows: Consider opening windows for a short period each day to allow fresh air to circulate. Just be sure to monitor the temperature and humidity levels to ensure that the plants are not being subjected to sudden or extreme changes.
• Inline duct fans: Inline duct fans can be installed in the ducting of your grow room to boost air circulation. These fans can be controlled with a thermostat or timer to regulate the flow of air into the grow space.

You should try to maintain a balance between air flow and humidity, as too much air flow can dry out the plants and too little can cause mold and mildew growth.

Sexing cannabis plants: when can a cannabis plant be sexed?

If like most growers you are cultivating weed for bud and not to breed you need to keep an eye out for the early signs of male plants. You must identify and remove any male plants from your grow as early as possible. Once those rascals release their pollen and fertilise a female flower, the production of resin glands will come to a halt and seeds will start to form in the buds making them pretty useless.

You can start sexing cannabis plants once the lights have been flipped to 12/12. You will begin to see the early signs of female plants first, these usually appear as little pistils and white hairs that grow around the nodes where the buds eventually form. Male plants on the other hand produce pollen sacks.

Train your plants early on

Cannabis plants are more plyable during the early vegetative stage, when their branches can easily bend.

To reap the full benefits from your cannabis plants, consider using training techniques such as LST, topping, mainlining or ScrOG, which allow you to manipulate the shape of the plant to encourage more efficient absorption of light, resulting in bigger yields.

Read our guide on training weed plants for bigger yields.

What are the signs of a stressed cannabis plant?

No nursery will ever grow without an issue popping up. Even the most dedicated growers will experience a problem occasionally. Recognizing a potential issue as soon as it arises will help you have a successful grow.

Some of the most common signs to watch out for include:

1. Yellowing or wilting leaves: This can be a sign of over or under watering, or deficiency in a specific nutrient. The only period where discolouration is accepted is when the plant is reaching the end of its flowering phase.
2. Bad smell: Your plant should at no point in the vegetative phase give out unpleasant smells. The only source of aroma is during flowering or when the plant is transitioning from the vegetative phase to the flowering phase. A bad smell could possibly mean rotting. Locate the source immediately.
3. Mold: Mold is commonly mistaken for trichomes as they look quite similar. But molds tend to appear in dense patches on the leaves and bud sites. The most common type of mold is white in color. Certain strains such as Cheese Feminised are known to have a certain level of resistance to developing mold, so growing with a strain like this will reduce the chances.
4. Slow growth: If the plant is not growing at its normal rate, this could be a sign of a root problem or a lack of nutrients.
5. Stunted growth: If the plant is growing but not as tall as it should be, this could be a sign of a light or temperature problem.
6. Leaf curling or distortion: This can be a sign of stress or a pest infestation.
7. Discoloration or spotting on leaves: This can be a sign of a fungal or bacterial infection.
8. Wilting even though the soil is moist: This can indicate root rot or a pest infestation.
9. Plant stretching: Your plant is supposed to be bushy. If you cannabis plant is growing tall with a lot of spaces in between branches, it is possible that the light source is not strong enough. Increase the lumen count.