Growing healthy cannabis plants requires not just the right environment, but also the correct balance of nutrients. When a cannabis plant lacks certain nutrients, it exhibits specific signs, and catching these deficiencies early can make all the difference in yield and quality. In this post, we’ll cover how to spot common deficiencies and what you can do to fix them.
1. Nitrogen Deficiency (N)
Signs:
- Yellowing leaves, especially older ones at the bottom
- Slow growth or smaller leaves
- Pale green overall appearance
Solution: Use a nitrogen-rich fertilizer. Adjust your feeding schedule to ensure plants are getting consistent nitrogen during the vegetative stage.
2. Phosphorus Deficiency (P)
Signs:
- Purple or red stems
- Dark green or blueish leaves
- Leaf tips and edges turning dark or bronze, often leading to necrosis
Solution: Increase phosphorus during the flowering stage with bloom-boosting nutrients. Organic options like bone meal or bat guano can help.
3. Potassium Deficiency (K)
Signs:
- Yellowing at the leaf edges
- Brown, scorched leaf tips
- Curling or crinkling of leaves
Solution: Add potassium sulfate or another nutrient blend that boosts K. Ensure your pH levels are balanced for proper nutrient uptake.
4. Calcium Deficiency (Ca)
Signs:
- Weak or brittle stems
- Brown spots on leaves
- Stunted root and leaf growth
Solution: Add calcium through supplements like lime or gypsum. A common calcium-magnesium (Cal-Mag) product can address this issue effectively.
5. Magnesium Deficiency (Mg)
Signs:
- Interveinal chlorosis (yellowing between leaf veins)
- Red or purple stems
- Leaf curling or crisping around the edges
Solution: Apply Epsom salts (magnesium sulfate) to your watering schedule, or use a Cal-Mag supplement.
6. Iron Deficiency (Fe)
Signs:
- New growth is yellow or white, while older leaves remain green
- Slow growth and small leaf size
Solution: Lower the pH to increase iron absorption, or use an iron chelate supplement to quickly correct the issue.
7. Zinc Deficiency (Zn)
Signs:
- Leaf tips yellow and die back
- Reduced leaf size and bunching at growth tips
- Distorted new growth
Solution: Zinc sulfate or a balanced micronutrient blend can help restore healthy growth.
8. Sulfur Deficiency (S)
Signs:
- Yellowing of new growth
- Stunted growth and weak stems
- Leaf curling
Solution: Amend with elemental sulfur or organic fertilizers like composted manure.
Prevention Tips
- pH Balance: Ensure your growing medium is at the correct pH (5.8-6.5 in soil) for proper nutrient uptake.
- Regular Feeding Schedule: Follow a consistent feeding schedule based on your plant’s growth stage.
- Monitor Runoff: Test your runoff water to ensure salts and nutrient buildups aren’t causing lockout.
