Cannabis Vegetative Stage: Explosive Growth

What is the Cannabis Vegetative Stage?

The vegetative stage (often called "veg") is the growth phase between the seedling stage and flowering. During veg, your plant focuses all its energy on building infrastructure: thick stems, large fan leaves, extensive root systems, and multiple branching sites.

Think of it as the "bodybuilding" phase. The bigger and healthier your plant grows during veg, the more bud sites it will have when flowering begins. This is why training techniques (topping, LST) are performed during this stage—to maximize the canopy and create an even spread of colas.

Key characteristics of the vegetative stage:

• Rapid vertical and lateral growth (can grow 2+ inches per day in optimal conditions)
• Development of the characteristic 5, 7, or 9-finger fan leaves
• High nitrogen demand for leaf and stem production
• Light schedule of 18+ hours keeps plants from flowering

Light Cycles: 18/6 vs 20/4 vs 24/0

Cannabis is a photoperiod plant, meaning it uses light duration to determine what season it is. Long days (18+ hours) signal summer, keeping the plant in vegetative growth. Short days (12 hours) signal autumn, triggering flowering.

During veg, you have several light schedule options:

• 18/6 (18 on, 6 off): Most popular. Gives plants a rest period while saving electricity. Many growers believe the dark period allows for root growth and stress recovery.
• 20/4: Slightly more light for faster growth. Common for autoflowering strains.
• 24/0: Continuous light for maximum growth speed. Higher electricity cost. Debate exists on whether plants benefit from any dark period.

For beginners, we recommend 18/6—it's proven effective, energy-efficient, and forgiving if you miss a light cycle occasionally.

Light Intensity (PPFD)

Unlike seedlings, vegetative plants can handle more intense light. Aim for 400-600 PPFD at the canopy level. If using LED grow lights, position them 18-24 inches above the canopy at 50-75% intensity. See our Grow Lights Guide for detailed PPFD charts.

Nutrients: Feeding for Growth

Vegetative cannabis has a high demand for nitrogen (N), the nutrient responsible for chlorophyll production and leafy growth. Most "Grow" or "Veg" nutrient formulas have elevated nitrogen levels with ratios like 3-1-2 or 4-2-3 (N-P-K).

Understanding N-P-K

• Nitrogen (N): Drives leaf and stem growth. Deficiency causes yellowing lower leaves. Toxicity causes dark green, clawing leaves ("the claw").
• Phosphorus (P): Supports root development and energy transfer. Less critical in veg than flower.
• Potassium (K): Regulates water uptake and enzyme activation. Important throughout the lifecycle.

Feeding Schedule

Start feeding nutrients at 1/4 to 1/2 strength once your plant has 4-5 sets of true leaves (typically week 3-4). Gradually increase to full strength over 2 weeks. Always follow the "less is more" principle—it's easier to fix a deficiency than nutrient burn.

Feed every other watering (water, feed, water, feed) or use a "feed-feed-flush" cycle for heavy feeders. Monitor your runoff PPM/EC to ensure you're not building up salt deposits. If runoff is significantly higher than input, flush with plain pH'd water.

Training: Topping, FIM, and LST

Plant training is the secret to maximizing yields. Left alone, cannabis grows like a Christmas tree—one main cola with smaller side branches. Training breaks this pattern, creating multiple main colas and an even canopy where every bud site gets optimal light.

Topping

Topping involves cutting off the main growth tip (apical meristem) to split it into two new main stems. This breaks "apical dominance" and redirects growth hormones to lower branches.

• When: After 4-6 nodes (sets of leaves), typically week 3-4 of veg.
• How: Use sterilized scissors to cut the main stem just above a node.
• Recovery: 3-7 days of slower growth while the plant redirects energy.
• Result: Two main colas instead of one. Can be repeated for 4, 8, or more tops.

LST (Low Stress Training)

LST involves gently bending branches and tying them down to expose lower growth to light. Unlike topping, LST doesn't damage the plant and is safe for autoflowers (which have limited time to recover from high-stress techniques).

• When: Start as soon as stems are flexible enough to bend without snapping.
• How: Use soft plant ties or pipe cleaners. Anchor to pot edge or a training ring.
• Result: Flat, even canopy with multiple colas at the same height.

For an in-depth guide to all training methods, see our Plant Training Guide.

Transplanting During Veg

As your plant grows, its root system expands. If roots become "bound" (circling the container bottom), growth stalls. Transplanting to a larger pot gives roots room to spread and access more nutrients.

Signs it's time to transplant:

• Roots visible at drainage holes
• Roots circling the bottom when you remove the plant
• Plant drying out faster than usual (roots have filled the pot)
• Stunted growth despite good conditions

Transplant schedule example:

1. Start in solo cup or 1-gallon pot
2. Transplant to 3-gallon pot at week 2-3
3. Final transplant to 5-7 gallon pot 1-2 weeks before flipping to flower

Tip: Transplant the day before your next watering (when soil is slightly dry). This makes the root ball easier to remove intact.

When to Flip to Flowering (12/12)

The decision to "flip" from veg to flower depends on several factors:

• Plant Height: Plants typically double in height during the flowering stretch. Flip when your plant is 50% of your maximum desired height.
• Training Completion: All topping and major LST should be done 1-2 weeks before flip to allow recovery.
• Root Development: Roots should have established in the final pot for 1-2 weeks before flip.
• Canopy Coverage: For SCROG growers, flip when the screen is 60-70% filled.

Indoor growers: Most flip after 4-8 weeks of veg. Longer veg = bigger plants = more yield, but also more space and resource requirements.

Autoflowers: No flip required! They automatically transition to flowering based on age (usually week 3-4), regardless of light schedule.