27. Recognizing and Addressing Common Cannabis Deficiencies and Toxicities

Introduction

Healthy cannabis plants rely on a delicate nutrient balance, and sometimes even minor imbalances can lead to visible deficiencies or toxicities. Recognizing early signs of these issues can help you correct course and keep your plants thriving. In this post, we’ll break down common symptoms of nutrient imbalances and provide solutions for each type.

Section 1: Identifying Common Cannabis Nutrient Deficiencies

• Nitrogen Deficiency: Leaves turn pale green to yellow, starting with older leaves.
  • Solution: Increase nitrogen levels in feeding schedule during vegetative growth, especially in soil or coco.
• Phosphorus Deficiency: Dark green or purplish hues, slow growth, and weak stems.
  • Solution: Boost phosphorus intake in flowering, especially in hydroponic systems.
• Potassium Deficiency: Yellowing or browning edges on leaves; leaves may curl or crinkle.
  • Solution: Add a potassium-rich nutrient, and ensure balanced ratios with nitrogen and phosphorus.
• Calcium and Magnesium Deficiencies: Spotting or rust-colored spots, weak stems.
  • Solution: Introduce Cal-Mag supplements, particularly in coco and hydro systems where these elements are less available.

Section 2: Recognizing Cannabis Nutrient Toxicities

• Nitrogen Toxicity: Dark, overly lush green leaves, curled leaf tips (the “claw” effect).
  • Solution: Flush soil with pH-balanced water and reduce nitrogen-rich feeds, especially during flowering.
• Phosphorus Toxicity: Leaf discoloration with burnt tips, often leading to a “lockout” of other nutrients.
  • Solution: Flush the root zone and reduce high-phosphorus fertilizers.
• Potassium Toxicity: Irregular growth patterns and other deficiencies, as potassium excess can lock out magnesium and calcium.
  • Solution: Cut back on potassium-heavy feeds and focus on nutrient balance.

Section 3: Strategies for Maintaining Nutrient Balance

• Regular Monitoring: Check leaves and stems frequently, and adjust feeding as needed based on growth stage and plant response.
• Proper pH Management: Keep pH levels in the optimal range (5.5–6.5 for hydro, 6.0–6.8 for soil).
• Use of Flushes: Periodic flushing helps remove nutrient buildup and can prevent both deficiencies and toxicities by balancing the root zone.

Conclusion:
Staying proactive with nutrient management helps prevent the majority of nutrient deficiencies and toxicities. By monitoring plant health, adjusting feeding schedules, and maintaining proper pH, you can keep your cannabis plants healthy and productive from seedling to harvest.