Fulvic Acid for Cannabis: A Guide to Mitigating Nutrient Damage
Discover how fulvic acid can be a key player in reducing nutrient damage in cannabis plants.
Cannabis nutrient burn: what the leaves show
Nutrient burn is damage from fertilizer salts that build up in the root zone faster than the plant uses them. The first sign is on the leaf tips: yellow, then tan, then brown and crisp. The tips curl down. Leaf blades stay dark green and look waxy. Growth slows.
Symptoms to check
- Brown, brittle tips on leaves across the canopy, not just the top.
- Leaf margins turn brown after the tips.
- Leaf blades curl down, a shape growers call clawing.
- Dark green color with a glossy surface.
- Dead spots that stop at leaf veins.
- New growth comes in small and twisted on heavy feed.
- Runoff reads high, or the root zone smells sour.
Where it starts
Tip burn shows on old and new leaves at the same time. Deficiencies do not. A nitrogen shortage starts on lower leaves with pale yellow between veins. A calcium shortage starts on new leaves with brown spots in the middle of the blade.
Cannabis Nutrient Burn Cure Time: How Long It Takes
Compare with light and heat damage
- Light burn: bleached white tops on the highest buds. Leaves below look normal.
- Heat stress: margins curl up, not down. Damage sits near the lamp.
- Nutrient burn: tips curl down and brown across the plant.
- pH lockout: yellow between veins, runoff pH out of range.
Fix
- Measure runoff EC or PPM. In soil, runoff above 2.5 mS/cm or about 1,250 PPM on the 500 scale points to salt buildup.
- Flush the pot with water at pH 6.0 to 6.5. Use 2 to 3 times the pot volume.
- Skip the next one or two feedings. Water only.
- Cut dead leaf tips with clean scissors. Leave the rest of the leaf in place.
- Restart feed at half strength, then raise it over 7 to 10 days.
Recovery
Burned tissue does not turn green again. New leaves should come in flat, even in color, with intact tips. That takes 5 to 14 days. Check runoff each week. Keep feed EC stable. If runoff climbs, lower feed strength before symptoms return.