Cannabis nutrition is where science meets art. While environmental factors like lighting and VPD create the foundation for growth, nutrition is what transforms that potential into dense, potent flowers. Get it right, and you'll see explosive growth and impressive yields. Get it wrong, and even perfect environmental conditions can't save your harvest.

This comprehensive guide covers everything from basic NPK ratios to advanced nutrient timing, helping both beginners and experienced growers master the feeding strategies used by commercial cultivators to maximize both yield and potency.

Understanding Cannabis Nutritional Needs

Cannabis as a Heavy Feeder

Cannabis plants are among the most nutrient-hungry crops you can grow. During peak flowering, a single plant can consume nutrients equivalent to feeding a small vegetable garden. This massive appetite means:

• Rapid nutrient depletion in soil and hydroponic systems
• Daily feeding requirements during peak growth phases
• Precise timing needs - wrong nutrients at wrong time kills yields
• Quality over quantity - nutrient quality directly affects final potency

The NPK Foundation: Nitrogen, Phosphorus, and Potassium

Nitrogen (N) - The Growth Engine

• Vegetative stage: 20-30% of total nutrients
• Flowering stage: 5-10% of total nutrients
• Functions: Protein synthesis, chlorophyll production, overall growth
• Deficiency signs: Yellow leaves starting from bottom, stunted growth

Phosphorus (P) - The Flower Builder

• Vegetative stage: 10-15% of total nutrients
• Flowering stage: 15-25% of total nutrients
• Functions: Root development, flower formation, energy transfer
• Deficiency signs: Purple stems, dark leaves, poor flower development

Potassium (K) - The Quality Controller

• All stages: 25-35% of total nutrients (highest requirement)
• Functions: Water regulation, disease resistance, trichome production
• Deficiency signs: Brown leaf edges, weak stems, reduced resin

Essential Secondary Nutrients

Calcium (Ca) - The Structure Builder

• Requirements: 150-300 ppm throughout growth
• Functions: Cell wall strength, root development, nutrient uptake
• Deficiency signs: Brown spots on leaves, weak stems, slow growth

Magnesium (Mg) - The Photosynthesis Core

• Requirements: 50-100 ppm throughout growth
• Functions: Chlorophyll center, enzyme activation, sugar transport
• Deficiency signs: Yellow between leaf veins, purple stems

Sulfur (S) - The Terpene Enhancer

• Requirements: 50-150 ppm throughout growth
• Functions: Protein synthesis, oil production, flavor development
• Deficiency signs: Yellow new growth, poor terpene production

Nutrition by Growth Stage

Seedling Stage (Weeks 1-2)

Nutritional Approach: Gentle introduction to nutrients

• Target PPM: 200-400 (0.4-0.8 EC)
• NPK Ratio: 1-1-1 or 2-1-1
• pH Range: 6.0-6.5 (soil), 5.5-6.0 (hydro)

Key Considerations:

• Cotyledons provide initial nutrition - external feeding minimal
• Root development priority - low-strength, balanced nutrients
• Gentle introduction - quarter-strength solutions maximum
• pH stability more important than nutrient strength

Recommended Feeding Schedule:

• Days 1-7: Water only or very weak nutrient solution
• Days 8-14: 1/4 strength nutrients every other watering
• Monitor: Watch for any signs of nutrient burn

Early Vegetative Stage (Weeks 3-4)

Nutritional Approach: Building the foundation

• Target PPM: 400-600 (0.8-1.2 EC)
• NPK Ratio: 3-1-2 or 4-2-3
• pH Range: 6.0-6.5 (soil), 5.5-6.0 (hydro)

Key Focus Areas:

• Nitrogen emphasis - supports rapid leaf development
• Root zone establishment - calcium and phosphorus important
• Growth hormone production - magnesium and sulfur essential
• Structural development - balanced secondary nutrients

Feeding Strategy:

• Daily feeding in hydroponic systems
• Every other day in soil systems
• Monitor runoff - should match input pH and be 10-20% lower PPM
• Increase strength gradually - 100-150 PPM increases weekly

Late Vegetative Stage (Weeks 5-8)

Nutritional Approach: Maximizing size and structure

• Target PPM: 600-900 (1.2-1.8 EC)
• NPK Ratio: 3-1-3 or 4-2-4
• pH Range: 6.0-6.5 (soil), 5.5-6.0 (hydro)

Optimization Focus:

• Maximum nitrogen uptake - plants can handle aggressive feeding
• Potassium increase - prepares plants for flowering transition
• Calcium emphasis - builds strong stems for heavy flowers
• Training support - nutrients support recovery from LST/topping

Advanced Techniques:

• Split feeding - different morning/evening nutrient ratios
• Foliar feeding - supplemental leaf feeding for rapid uptake
• Root zone additives - beneficial bacteria and enzymes
• Stress nutrients - extra calcium and magnesium before training

Transition Stage (Weeks 9-10)

Nutritional Approach: Preparing for flowering

• Target PPM: 700-1000 (1.4-2.0 EC)
• NPK Ratio: 2-3-4 or 1-3-2
• pH Range: 6.0-6.5 (soil), 5.5-6.0 (hydro)

Critical Changes:

• Reduce nitrogen - prevent delayed flowering and leaf overgrowth
• Increase phosphorus - supports flower initiation
• Maintain potassium - essential for flower development
• Boost calcium - strengthens branches for flower weight

Timing Considerations:

• Begin changes 1 week before switching to 12/12 lighting
• Gradual transition - sudden changes stress plants
• Monitor plant response - some strains need different timing
• Environmental coordination - adjust VPD for flowering conditions

Use our VPD Calculator to optimize environmental conditions during the critical transition phase.

Early Flowering Stage (Weeks 1-3 of 12/12)

Nutritional Approach: Supporting flower initiation

• Target PPM: 800-1200 (1.6-2.4 EC)
• NPK Ratio: 1-3-2 or 1-4-3
• pH Range: 6.0-6.5 (soil), 5.5-6.0 (hydro)

Flower Development Focus:

• High phosphorus priority - drives flower site development
• Moderate potassium - supports overall plant health
• Minimal nitrogen - just enough to maintain green leaves
• Calcium/magnesium boost - prevents deficiencies under stress

Common Challenges:

• Stretch management - avoid overfeeding nitrogen during stretch
• Flower site development - ensure adequate phosphorus availability
• Environmental stress - plants more sensitive during transition
• Training completion - final defoliation and training needs nutrition support

Mid Flowering Stage (Weeks 4-6 of 12/12)

Nutritional Approach: Maximizing flower development

• Target PPM: 1000-1400 (2.0-2.8 EC)
• NPK Ratio: 1-3-3 or 0-5-4
• pH Range: 6.0-6.5 (soil), 5.5-6.0 (hydro)

Peak Performance Nutrition:

• Maximum feeding strength - plants at peak nutrient demand
• Phosphorus emphasis - continued flower development
• Potassium focus - resin production and flower density
• Micronutrient attention - trace elements become critical

Quality Enhancement:

• Sulfur supplementation - enhances terpene production
• Silicon additives - strengthens cell walls and trichome stalks
• Beneficial bacteria - improves nutrient uptake efficiency
• Enzyme supplements - breaks down root zone buildup

Late Flowering Stage (Weeks 7-9 of 12/12)

Nutritional Approach: Finishing and quality optimization

• Target PPM: 600-1000 (1.2-2.0 EC)
• NPK Ratio: 0-1-3 or 0-2-4
• pH Range: 6.0-6.5 (soil), 5.5-6.0 (hydro)

Final Development Focus:

• Eliminate nitrogen - prevents delayed ripening and hay taste
• Reduce phosphorus - minimal amounts for basic function
• Emphasize potassium - drives final resin production
• Enhance flavor compounds - sulfur and trace elements

Quality Finishing Techniques:

• Controlled stress - slight underfeeding triggers resin production
• Terpene enhancement - specific nutrients boost flavor profiles
• Trichome development - optimal nutrition for maximum potency
• Harvest timing coordination - nutrition affects trichome maturation

Flush Stage (Final 1-2 weeks)

Nutritional Approach: Removing stored nutrients

• Target PPM: 0-200 (0.0-0.4 EC)
• NPK Ratio: 0-0-0 (water only or minimal supplements)
• pH Range: 6.0-6.5 (soil), 5.5-6.0 (hydro)

Flushing Benefits:

• Removes harsh taste - eliminates stored chemical nutrients
• Improves smoothness - reduces coughing and harshness
• Enhanced flavor - allows natural terpenes to dominate
• Better burn quality - ash burns whiter and cleaner

Flushing Techniques:

• Plain water only - most common approach
• Flushing agents - chelating agents for faster nutrient removal
• Gradual reduction - slowly decrease PPM over 2 weeks
• Monitor plant response - slight yellowing is normal and desired

Hydroponic vs Soil Nutrition

Hydroponic Nutrition Management

Advantages:

• Precise control - exact nutrient delivery
• Rapid adjustments - immediate response to changes
• Maximum efficiency - plants get exactly what they need
• Faster growth - optimized nutrition accelerates development

Key Practices:

• Daily monitoring - PPM, pH, and water temperature checks
• Complete water changes - weekly reservoir replacements
• Sterile techniques - prevent harmful bacteria growth
• Automated systems - dosing pumps and pH controllers

Target Ranges:

• PPM: More precise targeting (±50 PPM accuracy)
• pH: Tighter range (5.5-6.0) for optimal uptake
• Water temperature: 65-72°F for dissolved oxygen
• Dissolved oxygen: 5+ ppm for healthy root development

Soil Nutrition Management

Advantages:

• Buffer capacity - soil prevents sudden nutrient changes
• Beneficial microbes - living soil enhances nutrient availability
• Forgiveness - easier for beginners to manage
• Natural processes - mimics outdoor growing conditions

Key Practices:

• Soil testing - regular pH and nutrient level monitoring
• Organic amendments - compost, bat guano, kelp meal additions
• Watering techniques - proper wet/dry cycles for root health
• Living soil maintenance - feeding beneficial microorganisms

Target Ranges:

• PPM: Wider acceptable range (±100 PPM tolerance)
• pH: 6.0-6.8 for optimal nutrient availability
• Soil moisture: 40-60% for proper air/water balance
• Organic matter: 20-30% for healthy soil biology

Advanced Nutrition Strategies

Nutrient Timing and Cycling

Bloom Boosters:

• Week 3-5 flowering: High phosphorus supplements
• Week 6-7 flowering: Potassium boosters for density
• Final weeks: Terpene enhancers and flavor supplements

Foliar Feeding Programs:

• Early morning application - stomata open, maximum uptake
• Lights-off periods - prevents leaf burn and stress
• Targeted nutrients - calcium, magnesium, and micronutrients
• pH adjustment - 6.0-6.5 for optimal leaf absorption

Root Zone Optimization:

• Beneficial bacteria inoculation - mycorrhizae and rhizobacteria
• Enzyme supplementation - breaks down dead root matter
• Oxygen enhancement - air stones and hydrogen peroxide
• Root stimulators - hormones and vitamins for root development

Strain-Specific Nutrition

Indica Dominant Strains:

• Lower nitrogen tolerance - reduce N by 10-20% in flower
• Higher calcium requirements - dense growth needs strong structure
• Shorter feeding periods - faster maturation requires adjusted timing
• Potassium emphasis - supports dense, resinous buds

Sativa Dominant Strains:

• Higher nitrogen tolerance - can handle more N throughout cycle
• Extended feeding periods - longer flowering requires sustained nutrition
• Magnesium emphasis - supports larger leaf structures
• Trace element focus - enhances sativa terpene profiles

Autoflowering Varieties:

• Gentle approach - lower overall nutrient concentrations
• Faster transitions - quicker stage changes require responsive feeding
• Continuous feeding - no distinct vegetative/flowering separation
• Stress avoidance - minimal nutrient strength variations

Environmental Integration

Temperature Effects on Nutrition:

• Higher temps (80-85°F): Increase uptake rates, reduce concentration
• Lower temps (70-75°F): Slower uptake, maintain standard concentrations
• Temperature swings: Can cause lockout, maintain stability

Humidity and VPD Impact:

• Low VPD (<0.8): Reduced transpiration, lower nutrient uptake
• High VPD (>1.6): Increased uptake, risk of nutrient burn
• Optimal VPD (1.0-1.4): Maximum nutrient efficiency

Monitor environmental conditions with our VPD Calculator to optimize nutrient uptake based on transpiration rates.

CO₂ Enhancement Effects:

• Elevated CO₂ (1200-1500 ppm): Increase nutrient strength 15-25%
• Enhanced photosynthesis: Higher demand for all nutrients
• Temperature coordination: Higher temps with CO₂ increase uptake
• Accelerated growth: Faster consumption requires more frequent feeding

Common Nutrition Problems and Solutions

Nutrient Burn (Overfeeding)

Symptoms:

• Brown, crispy leaf tips - classic early sign
• Dark green leaves - excess nitrogen
• Stunted growth - plant energy diverted to dealing with excess
• Reduced yields - stressed plants produce less

Solutions:

• Immediate flush - 3x pot volume of pH-adjusted water
• Reduce concentration - cut nutrient strength by 25-50%
• Monitor recovery - should see improvement in 3-5 days
• Adjust feeding schedule - feed less frequently until recovery

Nutrient Deficiencies

Nitrogen Deficiency:

• Symptoms: Lower leaves yellow and drop, slow growth
• Solution: Increase nitrogen gradually, ensure proper pH
• Prevention: Regular feeding schedule, quality nitrogen sources

Phosphorus Deficiency:

• Symptoms: Purple/red stems, dark leaves, poor flowering
• Solution: Bloom boosters, check pH (phosphorus sensitive)
• Prevention: Adequate phosphorus in flower nutrients

Potassium Deficiency:

• Symptoms: Brown leaf edges, weak stems, poor resin
• Solution: Potassium supplements, ensure proper ratios
• Prevention: Quality nutrients with adequate potassium

Calcium Deficiency:

• Symptoms: Brown spots, weak growth, bud rot susceptibility
• Solution: Cal-mag supplements, check water quality
• Prevention: Hard water or calcium supplements

Magnesium Deficiency:

• Symptoms: Yellow between veins, purple stems
• Solution: Epsom salt foliar spray, magnesium supplements
• Prevention: Regular cal-mag supplementation

pH and Nutrient Lockout

Understanding pH Impact:

• Too low (< 5.5): Phosphorus, calcium, magnesium lockout
• Too high (> 7.0): Iron, manganese, zinc lockout
• Optimal range: 6.0-6.5 soil, 5.5-6.0 hydro
• pH swing benefits: Slight daily variations improve uptake

Lockout Solutions:

• pH correction - adjust to optimal range immediately
• Flush system - remove excess nutrients causing problems
• Chelated nutrients - more available forms of locked nutrients
• Patience - recovery takes 5-7 days minimum

Water Quality Issues

Hard Water Problems:

• High calcium/magnesium - can cause nutrient imbalances
• Alkaline pH - difficult to maintain proper pH levels
• Mineral buildup - accumulates in soil and hydro systems
• Solution: RO water or water treatment systems

Soft Water Issues:

• Lack of calcium/magnesium - requires supplementation
• Unstable pH - lacks buffering capacity
• Too pure - may leach nutrients from plants
• Solution: Add cal-mag and pH buffers

Organic vs Synthetic Nutrition

Synthetic Nutrients

Advantages:

• Precise control - exact NPK ratios and concentrations
• Immediate availability - plants can use nutrients instantly
• Consistent results - predictable plant responses
• Cost effective - generally less expensive per feeding

Disadvantages:

• Salt buildup - requires regular flushing
• Environmental impact - chemical runoff concerns
• Flavor impact - may affect taste if not flushed properly
• Root damage - high concentrations can burn roots

Best Applications:

• Hydroponic systems - precise control essential
• Commercial operations - consistent, predictable results
• Beginner growers - easier to understand and measure
• Fast turnaround - quick results for time-sensitive grows

Organic Nutrients

Advantages:

• Flavor enhancement - often produces superior taste
• Soil health - builds beneficial microbe populations
• Environmental safety - biodegradable and sustainable
• Buffer capacity - harder to overfeed or burn plants

Disadvantages:

• Slower response - nutrients must break down before availability
• Less precise - harder to control exact ratios
• Higher cost - premium organic nutrients expensive
• Complexity - requires understanding of soil biology

Best Applications:

• Soil growing - works with natural soil processes
• Quality focus - when flavor and smoothness priority
• Sustainable growing - environmental consciousness
• Long-term soil health - building living soil systems

Hybrid Approaches

Best of Both Worlds:

• Synthetic base with organic supplements
• Organic soil with synthetic finishing nutrients
• Living soil with targeted synthetic corrections
• Hydro with organic additives - enzymes and beneficial bacteria

Creating Your Feeding Schedule

Basic Feeding Calendar Template

Customization Factors

Strain Considerations:

• Indica: Reduce overall PPM by 10-15%
• Sativa: Extend flowering nutrition 1-2 weeks
• Autoflower: Reduce all concentrations by 25%

Environmental Adjustments:

• High VPD: Reduce concentration by 10-20%
• Low VPD: May need increased concentration
• CO₂ supplementation: Increase all levels by 15-25%
• Temperature: Adjust feeding frequency based on uptake rates

Conclusion: Nutrition as the Foundation of Quality

Cannabis nutrition is the bridge between genetic potential and actual harvest results. While genetics determine the ceiling for potency and yield, nutrition determines how close you get to that ceiling. Master growers understand that feeding cannabis isn't just about preventing deficiencies - it's about optimizing every aspect of plant metabolism for maximum quality and quantity.

Key Principles for Success:

• Start conservative - easier to increase than recover from overfeeding
• Monitor constantly - daily observation prevents major problems
• Adjust gradually - sudden changes stress plants and reduce yields
• Environmental integration - nutrition works best with optimal VPD and lighting
• Quality focus - the best nutrients are worthless without proper technique

Remember the interconnections: Lighting drives photosynthesis, VPD controls transpiration and nutrient uptake, and nutrition provides the raw materials for growth. These three elements work together to create the optimal growing environment. If you encounter nutrient-related problems, consult our complete troubleshooting guide for systematic diagnosis and solutions.

Ready to optimize your feeding program? Use our VPD Calculator to ensure your environmental conditions support maximum nutrient uptake and plant health.

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Complete your growing mastery with our guides on environmental controls, cannabis lighting optimization, DLI optimization, and troubleshooting common problems for professional-quality results.