Cannabis Nutrient Burn Fix: Flush and Reset Feed Strength

Nutrient burn fix: flush first, then cut feed strength

Nutrient burn comes from too much salt in the root zone. The fix is a flush, then a lower feed strength. Flush a 5-gallon pot with 10 to 15 gallons of pH-balanced water. Feed again at 50 percent of the last strength. New growth should look normal in 7 to 14 days. Leaves with burnt tips do not repair.

How to confirm it is nutrient burn

• Leaf tips turn brown, dry, and brittle. Damage moves inward along the leaf edge.
• Leaves sit dark green with a waxy surface.
• Tips curl down. Growers call this clawing.
• Upper and lower leaves both show damage. Light burn hits the leaves closest to the lamp.
• Runoff EC or ppm reads high against your input water.

Flush steps

1. Stop all nutrients. Water with plain water at the correct pH: 6.0 to 6.5 in soil, 5.5 to 6.0 in coco and hydro.
2. Run 2 to 3 times the pot volume through the medium. A 3-gallon pot needs 6 to 9 gallons.
3. Measure runoff EC and ppm. Stop when runoff reads within 0.3 EC of your input water.
4. Let the medium drain. Do not let pots sit in runoff.
5. Wait 1 to 2 days, then feed at half strength.

Feed targets after the flush

Most cannabis plants in veg sit between 1.0 and 1.6 EC. Flower runs 1.4 to 2.2 EC. Keep pH in range. Raise strength by 0.2 EC every 2 to 3 waterings if new growth stays green and flat.

Symptoms that point to pH lockout instead of burn: yellowing between veins, purple stems on new growth, and a runoff pH above 7.0 in soil. Check runoff pH before you add more nutrients.

Mistakes that make it worse

Do not flush with tap water above 300 ppm when you have a cleaner source. Do not feed right after the flush. Do not strip every fan leaf with a burnt tip. The plant needs those leaves to finish recovery. Do not treat burn as light stress without checking the canopy distance.

Recovery timeline

Day 0: flush. Day 1 to 3: leaves stop crisping. Day 4 to 7: new growth at the top comes in green. Day 7 to 14: full recovery at half to three-quarter feed strength. Burnt tips stay brown until the leaf drops off.

Prevention

Water to 10 to 20 percent runoff at every feeding. Track input EC against runoff EC. A runoff reading 0.5 EC above input means salt is building in the medium. Raise the runoff volume or lower the feed strength before damage shows.