Cannabis Growth Stages: Veg 

The vegetative stage is one of the most important phases in the life cycle of a cannabis plant. During this period, the plant focuses on developing strong roots, sturdy stems, and abundant leaves, which set the foundation for future bud production. 

For cannabis cultivators, mastering the vegetative stage can significantly influence the overall yield and quality of the final product. This article will explore the essential aspects of the vegetative stage, including environmental factors, nutrients, and techniques to optimize plant growth. This is part of our series covering the 7 Cannabis Growth Stages, which explores each phase in detail.

Understanding the Vegetative Stage

The vegetative stage of cannabis growth is where the plant development concentrates on producing foliage and developing a strong structure to support future buds. After germination and the seedling phase, the cannabis plant enters this stage, which typically lasts between four to 10 weeks, depending on the strain and environmental conditions. During this time, vegging plants will experience rapid growth, with their size often doubling or tripling.

Key characteristics of this stage include:

1. Rapid development of fan leaves
2. Thickening of stems and branches
3. Expansion of the root system
4. Increase in overall plant height

The vegetative stage is crucial because the growth and development during this period directly impact its ability to produce large, potent buds later. Proper care during the vegetative growth phase is essential to set up your marijuana plants for a healthy flowering stage and, ultimately, a successful harvest.

Photos: Kandid Kush

Optimal Conditions for Vegetative Growth

To ensure your cannabis plants thrive during the vegetative stage, it’s vital to create the ideal environment. Providing optimal conditions will help maximize plant development and growth. Here’s what you should focus on:

Light Cycle

Cannabis plants require an extended period of light during the vegetative stage. When growing indoors, the recommended light cycle is 18 hours of light and six hours of darkness each day (18/6). Some growers opt for a 24-hour light cycle to boost plant growth, but it’s essential to allow your plants some rest in the dark period, as this helps with root development and overall health.

Photoperiod plants require a change in the light cycle to initiate the flowering phase of growth, typically switching from 18 hours of light to 12 hours of light. This gives indoor growers control over how long they keep their plants in the vegetative stage, allowing them to extend this phase and grow much larger plants before flowering. This can be especially advantageous for growers who are limited by small plant counts, as larger plants produce higher yields, maximizing their harvest potential.

In contrast, autoflower plants do not need a change in the light cycle to begin flowering. They automatically transition from the vegetative stage to the flowering stage after about four weeks, regardless of the amount of light they receive. This makes autoflowers a more straightforward option for growers who want a quicker turnaround without having to manage light schedules.

Temperature

Cannabis plants thrive in temperatures between 70-90°F, with optimal growth occurring in this range. At the lower end, below 70°F, plant metabolism slows down, which can lead to slower growth and nutrient uptake. On the higher end, over 90°F, plants may experience heat stress, causing issues like wilting, nutrient lockout, and slower photosynthesis. When growing outdoors, you can mitigate heat stress with yucca root extract. Yucca shidigera root extract acts as a natural biostimulant, improving plant tolerance to heat by regulating water balance, reducing water loss, and enhancing overall resilience. Your plants will not only survive but thrive even during scorching summer months.

A notable physiological response occurs when the temperature drops during the night. A cooler night temperature, typically 10-15°F lower than daytime, encourages healthy transpiration, strengthens root development, and can promote the production of more vibrant colors in certain strains. However, excessive drops can shock the plant and slow growth. This temperature swing is vital for robust plant health, mimicking natural outdoor conditions that cannabis plants evolved in.

Humidity

Keep humidity levels between 40-70% during the vegetative stage. Higher humidity levels are beneficial early in the vegetative stage, but they should gradually be reduced as the plant grows to prevent mold or mildew issues.

Growing Medium

The choice of growing medium plays a significant role in how well your cannabis plant thrives. Whether you’re using soil, coco coir, or a hydroponic setup, the medium must be well-draining to prevent waterlogging and root rot. Many cannabis cultivators prefer organic soil mixes enriched with compost or worm castings, which provide a natural source of nutrients for your plants.

By controlling these environmental factors, you create an optimal setting for your plants to produce strong roots, stems, and leaves during vegetative growth.

Best Nutrients for the Veg Stage

Proper nutrition is essential during the vegetative stage to promote healthy plant growth and prepare the plant for a high yield in the flowering phase. The three main nutrients cannabis plants need during this phase are nitrogen, phosphorus, and potassium. These are often referred to as NPK on fertilizer labels.

• Nitrogen (N): Nitrogen is the most crucial nutrient during the veg stage because it promotes leaf and stem growth. It plays a role in chlorophyll production, which allows the plant to convert light into energy.
• Phosphorus (P): Phosphorus supports root development and is also essential for the early stages of bud formation as the plant prepares for the flowering phase.
• Potassium (K): Potassium helps plants regulate water and nutrient uptake, strengthens cell walls, and supports the overall health of the plant.

There are 15 other essential nutrients your plant needs, you can learn more about them in our “18 Cannabis Nutrients First Time Growers Need to Know” article. 

When choosing fertilizers, you have the option between synthetic nutrients or organic nutrient solutions. Both options can be effective, but synthetic options, like Advanced Nutrients, are salt-based nutrients that are typically formulated for fast absorption. 

Whereas many organic options, like Earth Juice Rainbow Mix, focus on feeding the microbes that benefit the soil ecosystem. Organics Alive provides an organic option that is formulated for fast absorption and comes in a water-soluble powder making it a sustainable option for both soil and hydroponic growers.

Organic Nutrients for a Healthy Veg Stage

For growers interested in a more natural approach, organic nutrients can be highly beneficial during the vegetative stage. Organic options not only feed the cannabis plant but also improve the health of the soil, leading to a more robust defense against pathogens. Some of the best organic nutrients for the veg stage include:

• Compost: Rich in nitrogen and beneficial microbes, compost is an excellent organic amendment for promoting vegetative growth.
• Worm Castings: Another natural nitrogen source, worm castings also improve soil structure and water retention.
• Fish Emulsion: High in nitrogen, fish emulsion is a popular organic fertilizer for boosting foliage growth.
• Bone Meal: A natural source of phosphorus, bone meal helps with root development and early flower formation.
• Kelp: High in potassium, trace minerals, amino acids, and growth hormones, kelp promotes strong root development, improves plant stress resistance and enhances overall growth during the vegetative stage.

Organic nutrients are often slower to release than synthetic fertilizers, making it essential to support a healthy soil food web to improve nutrient cycling.

Feeding Schedule and Techniques

Your feeding schedule will vary significantly depending on the growing method you use. For example, hydroponic systems, especially those utilizing rock wool, require more frequent feedings since there are no naturally occurring nutrients in the growing medium. In hydroponics, the plants rely entirely on the nutrient solution you provide, often needing daily feeding to meet their nutritional needs.

On the other hand, a living soil or super soil system operates very differently. In these setups, the feeding schedule largely depends on the richness and volume of the soil. Growers with a nutrient-rich, well-established soil ecosystem may only need to water their plants without adding additional nutrients, as the soil itself supplies everything the plants need. 

However, most growers choose to supplement with weekly nutrient teas to boost plant health and microbial activity. The frequency and type of feeding will depend on the specific needs of the soil and plants, with larger soil volumes generally requiring less frequent nutrient supplementation.

Start with a low dose of nutrients and gradually increase the amount as the plant grows. Overfeeding can lead to nutrient lockout, where the plant is unable to absorb nutrients properly. If the plant shows signs of nutrient deficiency, such as yellowing leaves (often a sign of nitrogen deficiency), adjust the feeding schedule accordingly.

Cannabis plants also benefit from foliar feeding, which involves spraying a diluted nutrient solution directly onto the leaves. This technique allows plants to absorb nutrients quickly and can be used as a supplement to root feeding. For example, advanced nutrient kits like those from Soilscape Solutions can provide targeted foliar feeds, ensuring plants receive essential nutrients directly through their leaves.

Common Challenges and Solutions in the Vegetative Stage

The vegetative stage is not without its challenges, and cannabis cultivators may encounter several issues that can hinder plant growth. Some of the most common problems include:

• Nutrient Deficiencies: The most common nutrient deficiencies during the vegetative stage are nitrogen and magnesium. Yellowing leaves or slow growth can indicate a lack of these nutrients. Adjusting your nutrient mix or supplementing with foliar sprays can help resolve these issues. 
• Pests: Aphids, spider mites, fungus gnats, and thrips are common pests that can attack cannabis plants during the vegetative stage. Regularly inspect your plants and use organic pest control methods like neem oil or insecticidal soap to protect them.
• Overwatering/Underwatering: Cannabis plants thrive in well-draining soil, and overwatering can lead to root rot. On the other hand, underwatering can cause plants to wilt and stunt their growth. Monitor soil moisture closely to ensure your plants get the right amount of water.

Preparing for the Transition to Flowering Phase

As the vegetative stage comes to an end, it’s essential to prepare your plants for the flowering phase, where bud production will take center stage. Signs that your plant is ready to transition include alternating nodes (branches growing in a staggered pattern), a reduction in vertical growth, and the appearance of pre-flowers.

To make the transition smooth, you can gradually reduce the light cycle from 18/6 to 12/12, simulating the shorter days of fall. This change signals to the plant that it’s time to shift its energy from vegetative growth to flower production.

How to Maximize Vegetative Growth

To get the most out of the cannabis veg stage, there are advanced techniques you can use to encourage more robust growth and better prepare the plant for flowering:

• Training Methods: Low-stress training (LST) and topping are two common methods to increase light exposure to lower branches and encourage bushier growth. These techniques help produce more bud sites and lead to higher yields.
• Microbial Inoculation: Adding beneficial fungi like mycorrhizae can improve nutrient uptake and promote faster plant growth. And azospirillum, a plant-growth-promoting bacteria can also be beneficial during this phase.  
• Pest Prevention: By utilizing an Integrated Pest Management plan, you can prevent pest pressure by spraying essential oils or micronized wettable sulfur. Ensuring your plants grow healthy throughout the vegetative phase will increase the quality and yield of your harvest.  

Veg Stage: Where Cannabis Plants Take Shape

The vegetative stage is the foundation of the cannabis plant’s life cycle, and how well your plant grows during this time will determine the success of your final harvest. By focusing on the proper light cycle, nutrient management, and advanced training techniques, cannabis cultivators can ensure their plants develop strong, healthy structures for optimal bud production.