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 (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