9.1 Detecting nutrient deficiencies

Cannabis plants can suffer from various nutrient deficiencies, which are recognizable by specific symptoms on the leaves and other parts of the plant. Here are some of the most common nutrient deficiencies, how to identify them, and methods for addressing them. Images aren't directly embedded, but I'll describe what the symptoms look like and how they can be treated.

1. Nitrogen deficiency

Symptoms:

  • Older leaves: Yellowing usually begins on the lower leaves and spreads upwards.
  • Leaves: Turn yellow with green veins (chlorosis).
  • Growth: Slow, the plant may appear stunted.

Treatment:

  • Nutrient supply: Use a nitrogen-rich fertilizer.
  • Adjusting pH: Make sure the pH is within the optimal range (6.0–7.0 for soil; 5.5–6.5 for hydroponics).
  • Using compost: If you use soil, compost can provide additional nutrients.

2. Phosphorus deficiency

Symptoms:

  • Leaves: Dark green to purple discoloration on older leaves. Discoloration may spread toward the leaf tips.
  • Growth: Slowed growth and reduced flowering.

Treatment:

  • Nutrient supply: Use a phosphorus-rich fertilizer.
  • Nutrient uptake control: Check that the pH does not affect the phosphorus nutrient uptake range.

3. Potassium deficiency

Symptoms:

  • Leaves: Yellow or brown spots on the leaf tips and edges, often with a burnt appearance.
  • Leaves: Discoloration and leaves may curl or dry.

Treatment:

  • Nutrient supply: Use a potassium-rich fertilizer.
  • Watering: Ensure adequate watering and good drainage, as potassium is not absorbed well in wet conditions.

4. Calcium deficiency

Symptoms:

  • Leaves: New leaves often show brown spots or necrosis. Leaves may also be distorted and deformed.
  • Flowers: Flowers may be small or deformed.

Treatment:

  • Nutrient supply: Use a calcium fertilizer or lime.
  • pH control: Ensure that the pH is within the optimal range, as calcium is not readily available at pH values ​​below 6.0.

5. Magnesium deficiency

Symptoms:

  • Leaves: Older leaves exhibit interveinal chlorosis, in which the veins remain green while the area between the veins turns yellow. The leaves may also develop brown spots and die.
  • Leaves: Leaves may bend or curl upward in the middle.

Treatment:

  • Nutrient supply: Use a magnesium fertilizer or Epsom salt (magnesium sulfate).
  • pH control: Check the pH level, as magnesium is not absorbed well at very low or high pH levels.

6. Iron deficiency

Symptoms:

  • Leaves: Newer leaves exhibit interveinal chlorosis, in which the leaves turn yellow but the veins remain green. These symptoms often begin at the tips of the new leaves.
  • Growth: Slow growth and stunted leaves.

Treatment:

  • Nutrient supply: Use iron chelate or an iron-containing foliar fertilizer.
  • pH control: Check the pH, as iron is poorly available at pH values ​​above 7.0.

7. Sulfur deficiency

Symptoms:

  • Leaves: New leaves show a general yellowing. The leaves may also develop small brown spots and die.
  • Growth: Slowed growth and weak plant growth.

Treatment:

  • Nutrient supply: Use a sulfur fertilizer or gypsum.
  • pH control: Ensure that the pH is within a range that does not interfere with the absorption of sulfur.

8. Zinc deficiency

Symptoms:

  • Leaves: New leaves may have small yellow spots or chlorosis, often with a compacted leaf structure.
  • Growth: Reduced growth and delayed leaf growth.

Treatment:

  • Nutrient supply: Use a zinc fertilizer or zinc supplement.
  • pH control: Ensure that the pH is within the optimal range, as zinc is poorly available at extreme pH values.

Summary and prevention

  1. Regular monitoring:
    • Check your plants regularly for signs of deficiencies and adjustments in nutrient schedules.
  2. pH control:
    • Maintain the correct pH for your medium to optimize nutrient uptake.
  3. Nutrient intake:
    • Use balanced nutrient mixtures and adapt them to the specific needs of your plants.
  4. Use of supplements:
    • If there are signs of deficiencies, targeted supplements can help to quickly resolve the problems.

With proper care and regular checks, you can identify and correct nutrient deficiencies early on to ensure the healthy growth of your cannabis plants.