The vegetative stage of weed is one of the most crucial phases in the cannabis life cycle. It follows the seedling stage, when the plant breaks loose from its shell and root formation begins. Therefore, you must implement specific methods to ensure it flourishes, giving you, the grower, a bountiful harvest.
But before we discuss the details of the proper care approach, it is important to better understand this growth phase and why it is particularly essential.
Why growers give utmost importance to the vegetative stage of weed
Cannabis plants undergo crucial developments during the vegetative stage, which growers pay special attention to.
Leaves and branches grow in spurts as the plant’s structure shows itself. The roots form an expansive network in the soil to create the ability to absorb water, oxygen, and nutrients, and to form a strong foundation for the flowering stage.
One tell-tale sign that a cannabis plant has entered the vegetative stage is when the seedling develops five to seven sets of pointed leaves.
Vegetation for cannabis plants usually starts during the third and fourth weeks of growing. As the cycle progresses, the crops will grow taller and fuller. You can also expect lateral growth, making your plants appear bushier. The plants will begin to form white pistils, which can indicate their sex, but it will take sometime before you can be certain.
The vegetative stage is when the plant is the easiest to manipulate. Growers train their beloved crops to form in their desired shape during this stage, but more on this later.
The vegetative stage of autoflowers vs. photoperiod plants
Photoperiod cannabis plants require a specific amount of light exposure during the vegetative stage to initiate flowering, as you will read in the following sections.
On the other hand, you have autoflowering plants. As the name suggests, these crops will flower regardless of how much light you expose them to. The ideal light cycle during the vegetative stage of autoflowers is 20 hours of exposure and four hours of darkness.
Unlike photoperiods, autoflowers don’t require much hands-on attention and generally don’t respond well to high-stress training techniques. However, trimming and low-stress training during the first five weeks can help maximise yields and reduce the risk of mould development.
The low-maintenance trait of autoflowering cannabis plants makes them a more suitable option for beginner growers who have zero to little experience. A downside, however, is that these crops tend to be smaller than photoperiods, growing to an average height of up to 105 cm (3.5 ft) indoors and up to 125 cm (4 ft) outdoors. Photoperiod plants can grow up to 200 cm (6.5 ft) outdoors and 125 cm (4 ft) indoors.
If you’re just starting your cannabis cultivation journey, autoflowering plants are a good introduction. There may be downsides, but the process can provide enough experience to transition into more advanced growing techniques.
The vegetative stage of weed from a scientific lens
We’re about to get a bit nerdy, but knowing the science during the vegetative stage is essential in gaining a deep understanding. Don’t worry; all this information will be digestible.
Understanding photosynthesis
Cannabis relies on the process of photosynthesis for energy during this growth phase. It’s a crucial aspect that could determine its state of health as it grows.
Here is the process in a nutshell: light from the sun or an artificial source gets absorbed by chlorophyll molecules called chloroplasts the moment it touches the leaves. It is then converted into chemical energy, which gets stored within.
All that stored energy will later be used to split water molecules, turning them into oxygen and hydrogen. When the oxygen is released into the atmosphere, the hydrogen combines with carbon dioxide to produce glucose, which provides more energy for the plant to spur healthy growth.
Photosynthesis generates energy and balances the plant’s internal habitat by releasing excess oxygen and hydrogen.
Given this knowledge, we can use nature’s processes to the plant’s advantage. That brings us to the following section, which covers the essential factors in providing proper care during the vegetative stage.
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Proper care during the growth phase: The essential factors
Every grower must take care of these essential components: light exposure, water and nutrient levels, humidity, and temperature, and pest prevention, which this section discusses in detail. We will also cover transplanting, a needed step to promote root growth and enhance nutrient intake.
1. Light exposure during veg
The vegetative stage is when cannabis plants require the most light exposure. Whether grown indoors or outdoors, your herbs must have at least 13 hours of light daily. However, experts recommend going between 18 and 24 hours for optimal results. For photoperiod plants, 18 hours of light and six hours of darkness is the ideal amount of exposure.
Photosynthetic photon flux density (PPFD), a.k.a.the amount of light touching the plant, is critical to maximising photosynthesis results. For the vegetative stage, research suggests using PPFD levels of 400-600, which growers can have better control over when done indoors using artificial lighting. More on this later.
Strain type also plays a role in determining how much light exposure your plants need. You don’t need to make any changes for the vegetative stage of autoflowers since they will bloom on their own. Otherwise, you must switch the cycle to 12 hours daily to initiate flowering.
2. Watering during veg
First, let’s address water levels. As mentioned earlier, the growth spurts happen during this particular growth stage in the cannabis life cycle. That said, plants need significant water during the vegetative phase.
However, overwatering is an issue you need to avoid as a grower. It can deprive the roots of air, causing them to rot. That begs an important question: How much watering is enough during the vegetative stage of cannabis?
Here’s a rule of thumb that most experts agree on: watering should be every two to three days during this growth phase, especially during the growing season that usually happens around the second and third quarter of the year. As for the amount, keep it at a small amount of up to 250 ml (8.5 oz) per day at first, and increase to 1000 ml (34 oz) as the stage progresses.
And to avoid flooding your plants, here’s a pro tip: the next round of watering only happens once the soil feels dry to the touch after the first. Do this until you’ve completed the recommended amount for the day.
Water quality is another essential factor to consider. PH levels matter, for one, with the consensus being 6 to 7. For soil growers, 6.5 is the recommended sweet spot.
Tap water is usually acceptable, as long as it is rid of calcium and chlorine to avoid damaging the plants. But ideally, veteran growers and cannabis connoisseurs would advise using purified reverse osmosis water or collected rainfall.
3. Nutrients during the veg stage
Just like humans, cannabis plants need nutrients for optimal growth. In this case, there are three primary macronutrients: nitrogen, potassium, and phosphorus.
Nitrogen aids photosynthesis, while phosphorus helps in efficient energy storage, root development, and metabolism. Meanwhile, potassium gives the plant a healthy colour, noticeable aromatics, and furthers growth.
Then, there are the supplementary nutrients: calcium to manage salt content in the soil, magnesium to aid in metabolising carbohydrates, and sulphur to help produce chlorophyll, along with the vitamins and amino acids to combat diseases.
Providing nutrients during the vegetative stage of weed will depend on how far along the plant is during this growth phase. On the onset, experts recommend using organic fertilisers with a lower Nitrogen-Phosphorus-Potassium (NPK) ratio of 2:1:2.
Regarding specific measurements, experts advise using 200 parts per million (PPM) of Nitrogen, 120 ppm of Phosphorus, and between 200 to 250 ppm of Potassium. Recommended feeding time is usually after transplanting.
The ratio increases when the plants reach the sixth week to fortify leaf development. Around this time, the recommended NPK ratio is 10:5:7. These levels will slightly taper during the final week of vegetation, dropping to a balanced ratio of 7:7:7.
4. Humidity and temperature
Relative humidity (RH) measures the amount of water vapour in the air. Maintaining proper levels affects yield during harvest and prevents mould development.
Measuring ideal RH levels will depend on the environment plants are accustomed to. Those that grow in warmer climates require higher levels, while the opposite applies to plants in colder regions.
It’s usually recommended to use moderate RH levels around 50 to 70% during the growth phase. Wetness is a key indicator in managing these levels, and too much moisture means humidity is likely higher than needed.
And since root development begins during this phase, water intake increases. Therefore, recommended RH levels should be lowered by 5% each week.
At the same time, temperatures must be managed to manage metabolism rates. It is ideal to keep temperatures within 22-28°C (71-82°F) during the day and between 18-22°C (64-71°F) at night.
5. Pest prevention and control
As it is with growing any plant, the threat of pest infestation is inevitable when cultivating cannabis crops.
Whiteflies, spider mites, fungus gnats, and aphids are common pests that give cannabis growers headaches. These little annoyances breed quickly, thrive in moist environments, and either attack the plants or compromise soil and root quality.
As always, prevention is better than finding remedies and salvaging the remains of the destruction that transpired. It is particularly crucial during the growth phase to ensure healthy growth for your young plants and, ultimately, a bountiful harvest.
For starters, it pays to have a sanitary growing environment, and that goes without saying. Immediately get rid of dead plant material, debris, and weeds that are not related to the magic herb. Next, keep humidity and temperature levels at bay to regulate moisture build-up.
Pesticides should be the last resort, and if you must use them, choose organic variants like neem oil and spinosad. Another natural option is to have predatory insects attack. Lady bugs, predatory mites, and lacewings prey on spider mites and aphids, helping keep your plants pest-free.
6. Transplanting
Transplanting is the process of moving cannabis plants from one container or growth medium to another. This allows your precious herbs to develop a more robust root system, which ultimately promotes better nutrient absorption. It also prevents overcrowding, which can lead to stunted growth.
The vegetative stage of weed is the best time to transplant because a more solid root system has already developed.
Transplanting usually takes four steps, depending on how you do it.
- Pick out the preferred container and the intended growing medium. Seasoned cannabis growers would recommend using fibre as a material because it will decompose over time and allow the natural expansion of roots. Soil is still the preferred growing medium because it is available, easy to use, and can balance nutrients, oxygen, and water retention.
- Uproot the plant. This process requires a gentle touch. Experienced cultivators recommend watering it first to loosen the soil and alleviate stress on the roots. Once moist enough, invert the old container to allow the plant to slide out naturally.
- Move the plant into the new container. Place it in the centre after digging a hole big enough to fit the root ball. Fill the hole with the chosen growing medium and ensure there aren’t gaps for air pockets.
- Aftercare. The new container should ideally be in an environment that provides sufficient water, sunlight, and proper humidity and temperature levels.
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Indoor vs. outdoor cultivation
Contrasting environmental factors means cultivators take widely varying approaches to growing indoors and outdoors. While the latter provides more space for plants to grow freely, the former allows them more control over the essential factors mentioned above.
In this section, we will take a closer look at the differences between growing during the vegetative stage indoors and outdoors.
The vegetative stage indoors
Indoor cannabis growing gives cultivators more freedom regarding light exposure, water levels, humidity, and temperature control, which we will focus on in this section. Controlling these environmental factors allows growers to do it year-round.
Light exposure
Experts recommend using LED bulbs since they can best simulate sunlight compared to other artificial light sources. Positioning matters, and many seasoned growers advise placing lights either below the canopy or on the side of the plant. This ensures that every part gets sufficient lighting for healthy growth and maximum yields.
Watering
An automatic drip irrigation system is your best bet for indoor growing. It allows for efficient nutrient delivery, ensuring a balance for greater chances of a healthy harvest. Drip irrigation systems also work in small spaces, making them a flexible option if you work within a limited real estate.
Humidity
Humidifiers are essential for regulating humidity levels in a cannabis grow room. As a guideline, smaller appliances work best for rooms within 30 m² (300 sq ft). Medium humidifiers fit best in a grow room that can get as big as 45 m² (500 sq ft). Larger humidifiers are for spacious rooms as big as 90 m² (1000 sq ft).
Temperature control
HVAC systems are the best way to go in terms of regulating temperature. And in this case, you’re measuring BTUs as a reference for which unit to get. Using the exact dimensions, a 30 m² grow room needs around 7,000 BTUs per hour. The 45m² room typically requires 12,000 BTUs per hour, while the 90 m² needs around 18,000.
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The vegetative stage outdoors
If you grow outdoors, nature and, in most cases, space are on your side. Therefore, the approach is slightly different. While there is less control over these essential growing factors, unlike indoor cultivation, outdoor growing tends to be less pricey without the need for added appliances.
Light exposure
Like indoor growing, the proper positioning of plants matters when cultivating cannabis outdoors. In this case, you’d want a spot in your garden where crops receive the most sun exposure. Adequate spacing between plants is also necessary to achieve this goal.
Watering
Rain is one of the most reliable sources of water when growing outdoors. However, you can use a drip irrigation system to ensure sufficient hydration for your plants. The beauty of these systems is that they come in automated variations, allowing a more hands-off approach for busy growers.
Humidity and temperature control
You can’t regulate or control humidity and temperature levels when growing outdoors, but you can adjust your approach. For one, you can use bigger containers to keep plants cool during hotter months. You can also use silica supplements to make them more resistant to heat.
But if you want a less manual approach, you can choose strains that adapt well to the weather or your region. Shiva Skunk and Afghani #1 adapt well to heat, while Jamaican Pearl and Sensi Skunk thrive in cold environments.
5 Common grower mistakes during the vegetative stage
Because the vegetative stage is a crucial growth phase, mistakes can be costly. Avoid the headaches and potentially irreparable consequences by knowing the common errors.
1. Using incorrect fertiliser amounts
In an earlier section, we mentioned the proper nutrient levels for your plants. It is crucial to follow these measurements to avoid overfeeding or nutrient deficiency, both of which are detrimental to growth and yields.
So, how can you tell if your plants suffer from overfeeding and nutrient burn? Since bud development hasn’t begun during the vegetative stage, you will see it in the leaves. There will be visible signs of browning on the edges, then the tips. That discolouration is otherwise known as leaf scorch or burning.
Nutrient deficiency in cannabis plants manifests through leaf discoloration, similar to overfeeding. However, you will notice stunted growth, which usually denotes a lack of phosphorus.
2. Mismanaging pH levels
The pH levels in cannabis cultivation refer to the acidity level of the chosen growing medium. Keeping these numbers in check ensures a better chance of high yields and healthy growth.
PH levels range from zero to 14, with the lowest range being the most acidic. As the numbers go up, so do alkaline levels. Most seasoned cultivators recommend keeping pH levels between 6 and 7 during the vegetative stage.
This sweet spot allows for optimal absorption of all three needed nutrients. As growth progresses, pH levels gradually increase.
3. Improper spacing
Cannabis plants need adequate spacing during the vegetative stage for optimal nutrient intake. Being too close to each other deprives the roots and leaves of the full benefits of fertilisers, water, light exposure, and carbon dioxide.
Experts recommend leaving 1.5 to 3 feet of space (18 to 36 inches) between plants as a rule of thumb. If you’re growing indoors, you can make the necessary adjustments by transplanting or limiting the number of plants to accommodate your space limitations.
4. Disregarding pest management
Many growers tend to be so busy that they unintentionally neglect proper pest management practices. They either leave the space untidy or forget to implement preventive measures. Before they knew it, spider mites had already infected most of their crops.
Take the time to inspect your beloved crops regularly and remove any damaged parts to prevent the spread to the entire plant. It pays to practise having a clean environment devoid of clutter and proper hygiene, like hand washing.
These simple steps may save you from the headaches of a full-blown pest infestation.
5. Lack of research and forethought
Based on the list of essential factors for proper care, cannabis cultivation involves many moving parts and requirements.
However, many novice growers commit the crucial error of beginning a cultivation venture without researching and preparing beforehand. It pays to understand the basics of the plant’s life cycle, photosynthesis, and all the components mentioned earlier.
Thankfully, the internet is a vast resource of necessary information. You can likewise consult seasoned growers for input, firsthand knowledge, and tips and tricks. And our blog, of course!
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5 FAQs about growing weed during the vegetative stage
For many growers, the vegetative stage of weed is the most challenging phase. This section addresses some frequently asked questions to help you prevent these common mistakes and ensure a satisfying harvest.
Coco coir is one of the options you can go with because it can help keep pH levels balanced, which is essential for the vegetative stage of weed. Likewise, it retains water well enough. And if you’re all about environmental friendliness, it is a very sustainable option.
Perlite is another excellent option because it provides good drainage and air distribution, which are crucial during this growth phase.
Some veteran cultivators use rock wool as a growing medium. Not only does it enable proper root development, but it also balances nutrient levels and prevents waterlogging. Likewise, rockwool is sterile enough to ward off pests.
Generally, smaller pots are used for growing cannabis indoors than when growing outdoors.
Indoors: During the early phase of the vegetation stage when plant height is 15 to 30 cm (6 to 12 inches), the recommended pot size is 2 to 4 litres (0.5-1 gallon) in capacity. When growth reaches 60 cm (25 inches) , pot size increases to around 10 to 20 litres (2.5-5 gallons), depending on the space you have in your room. Before flowering, you could go for bigger pots once more (up to 30 litres, or 7 gallons).
Using much larger pots isn’t advisable because more soil holds more water than the roots can handle, which could lead to their rotting.
Outdoors, bigger pots are used, with for example a 4-litre (1 gallon) pot after the seedling stage, 20 to 25-litre (5 to 7 gallons) pots during vegetation, possibly increasing it to 40 litre (10 gallons) pots before flowering.
Most growers cultivate cannabis for harvesting buds. In that case, you’ll need female plants. These crops develop two hair-like structures called stigmas or pollen catchers. They are usually white, but some develop yellow and red hues.
Male plants, on the other hand, have tiny pollen sacs in the nodes, the area where the stem and leaf meet. Males should be removed during the vegetative stage because they would compromise the overall quality of the harvested product due to its seed production. 
For photoperiod plants, this growth phase can last between 3 and 16 weeks. The duration will depend on the environment and whether you’ve provided the plants with sufficient light exposure, water, nutrients, and all the other essentials mentioned in the previous section.
You can decide when to switch to the flowering stage based on the space and time you have available and the results you’re aiming for. If you prefer smaller plants and a quicker turnaround, you can switch to the flowering stage sooner. However, if your goal is to grow the largest possible plants and achieve maximum yields, you might choose to extend the vegetative stage.
Some growers choose to lengthen the vegetative stage even further, especially for cloning purposes.
Pre-flowers, which are underdeveloped buds that appear in the nodes, are the most telling visible sign that the plant is ready to transition.
You will notice size changes. The plant will gain less height every week and grow horizontally by developing more leaves and branches. Leaf structure also evolves, with some foliages appearing narrower. Others may have serrated edges.
Noticeable aromas develop as the plant progresses to the flowering stage. Some may carry a sweeter, fruity smell, while others tend to have a more skunk odour. It all depends on strain variety.
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Transitioning to the flowering phase
Plants usually begin moving towards the flowering phase around four to six weeks after vegetation begins. This is when you start to see the signs mentioned in the above section.
Changes in light exposure are crucial for this transition. The light cycle should shift from 18 or 24 hours of daylight to 12 hours of light and 12 hours of darkness to initiate flowering.
Additionally, the nutrient supply should be adjusted. During the flowering phase, plants require more calcium, magnesium, and other macronutrients to support healthy bud development.
Photos of the vegetative stage by week
Here are some photos for reference to give you a clearer idea of how cannabis plants look during each week of the vegetative stage. Noticeable development begins around week three when leaves grow more abundantly.
You should have transplanted the crops to a bigger medium for healthy growth by week four. By week eight, you should see fuller foliage development.
An introduction to training methods
Training is the process of manipulating plant growth and shape. Applying training methods can also help maximise yields while managing height, which is especially helpful for indoor cultivation.
There are several ways to train a cannabis plant. Low-stress training (LST) bends the stems to enable horizontal growth. Supercropping is a notch higher, where you soften the stems by bending them at a more extreme angle.
The Screen of Green (ScrOG) method involves placing a mesh screen over plants to manipulate their growth. Some practices, like topping and FIMing, cause deliberate damage to the plants.
A time of growth
This extensive piece can serve as your ultimate guide to the vegetative stage of cannabis. It includes the key factors to promote healthy growth and the mistakes you should avoid. Now it’s your turn – feel free to share some of your tips in the comments below!
- Disclaimer:Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.
