Nutrient burns can destroy harvests. Early detection, immediate action and cure for over-fertilised cannabis plants.
Over-fertilisation (nutrient burn) is a common and dangerous mistake in cannabis cultivation:
**What is nutrient burn?
Nutrient burn occurs when cannabis receives more nutrients than it can process. The excess salts accumulate in the plant and cause "burns".
**Recognise early signs:**
*Stage 1 - Slight over-fertilisation:*
- Dark green leaves (too much nitrogen)
- Shiny, "greasy" looking leaves
- Slightly curled leaf tips
- Minimal brown leaf tips
- Slower growth despite lots of nutrients
*Stage 2 - Moderate over-fertilisation:*
- Significant brown leaf tips and edges
- Yellow/brown discolouration between leaf veins
- Leaves become stiff and brittle
- "Clawing" - leaves bend downwards
- Salt deposits on the substrate surface
*Stage 3 - Severe over-fertilisation:*
- Massive brown/black leaf areas
- Entire leaves die off
- Growth stops completely
- Flowers turn brown/slimy
- Roots burn and die
**Causes of Nutrient Burn:**
*Fertiliser dosage too high:*
- Manufacturer's instructions exceeded
- Different fertilisers combined without adjustment
- Concentration not tested for EC value
- "More is better" mentality
*pH problems intensify Burn:*
- Incorrect pH value increases uncontrolled nutrient uptake
- pH fluctuations additionally stress plants
- Lockout situations due to pH problems
*Substrate problems:*
- Pre-fertilised soil + additional fertiliser
- Old salt deposits in reused soil
- Poor drainage keeps salts in the root zone
**Immediate measures for Nutrient Burn:**
*Stop all fertilisation:*
- Stop all nutrient additions immediately
- Only give pure, pH-adjusted water
- At least 1-2 weeks fertiliser break
*Flushing:*
- flush 3 times the volume of the pot
- use pH 6.0-6.5 water
- Example: 10L pot = 30L flushing water
- Until drain water has a low EC value (<0.4)
*Remove affected leaves:*
- Remove severely damaged leaves (>50% brown)
- Leave slightly affected leaves on
- Use clean, sharp scissors
- Disinfect wounds with cinnamon
**pH correction during treatment:**
*stabilise pH value:*
- Keep constant 6.0-6.5 (soil)
- Keep constant 5.5-6.0 (Hydro)
- Re-measure pH after each rinse
- Stable pH values help with recovery
**Recovery phase (2-4 weeks):**
*Slow recovery:*
- First week: water only
- Second week: 25% normal fertiliser dose
- Third week: 50% normal fertiliser dose
- Fourth week: 75% normal fertiliser dose
*Monitoring during recovery:*
- Measure pH and EC daily
- Check new leaves for healthy growth
- No further stress factors (heat, training)
- Documentation for future grows
**EC value management:**
*Optimal EC ranges:*
- Seedlings: 0.4-0.8 mS/cm
- Vegetative: 0.8-1.4 mS/cm
- Flowering: 1.4-2.0 mS/cm
- Flushing: 0.0-0.4 mS/cm
*EC measurements:*
- Measure before each fertilisation
- Compare input and output (drain)
- Increasing output = Salzaccumu
Signs of over-fertilization include scorched leaf tips, yellow or brown spots on the leaves, and a general slowdown in growth. Also check the pH level and nutrient concentration in the growing medium.
Immediately reduce the nutrient supply and rinse the roots with clean water to flush out excess nutrients. Then let the plants recover in a low-nutrient medium.
Start with a weaker nutrient solution and gradually increase the dose while monitoring the plants. Be sure to check the pH and EC levels regularly.
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