Quick answer
Nutrient burn comes from too much fertilizer salt in the root zone. Fix it by flushing the pot with pH-adjusted water until runoff reads low and clear, then restart feeding at a reduced strength once new growth looks normal. Brown tips will not heal, so score recovery on new leaves, not old damage.
adjust ec for marijuana nutrient burn
Signs of nutrient burn
Burn shows up first where nutrient salts collect: leaf tips and margins. Look for these markers before you change anything.
- Brown, crisp tips on upper and middle leaves, moving inward along the edge
- Dark green, glossy leaves with claws that curl downward, a nitrogen excess pattern
- Edges that crumble when you touch them
- Slow stretch with tight node spacing
- A white salt crust on the medium surface or pot rim
Rule out lookalikes first. Light burn hits only the top canopy and bleaches tissue. pH lockout shows patchy yellowing between veins. Underwatering causes a soft droop with flexible stems.
Before you start
- Calibrated pH meter and EC or PPM meter
- Room-temperature water, dechlorinated or filtered
- Drain tray or saucer to catch runoff
- pH up and pH down solution
Step-by-step fix
- Stop all nutrient feeding and additive doses.
- Measure the EC or PPM of your runoff and write it down.
- Pour pH-adjusted water through the medium at 2 to 3 times the pot volume, splitting the flush into passes.
- Test runoff again after the last pass and confirm the reading has dropped toward your plain water baseline.
- Let the medium drain and then dry back to roughly 50 percent moisture before the next watering.
- Snip only the dead, brown tip tissue with clean scissors and leave green leaf area intact.
- Restart feeding at 50 percent of the previous strength, or lower the EC by 0.3 to 0.5.
- Set water pH to 6.0 to 6.8 in soil and 5.5 to 6.2 in coco or hydro.
Flush volume by container size
A 5-gallon pot needs roughly 10 to 15 gallons of water to clear heavy salt buildup. Water slowly in three passes and let each pass drain before the next. Flushing a dry pot drives channels through the medium, so water the plant one day before the flush.
how to fix nutrient burn in cannabis plants
Reading runoff numbers
Runoff EC well above your input EC means salts are sitting in the medium. Runoff well below input usually means the medium is holding nutrients and the plant is underfed, not burned. Track both numbers each week so one bad reading does not trigger a flush you do not need.
Recovery timeline
New leaves typically show normal color and flat tips within 5 to 10 days. Full canopy recovery takes 2 to 3 weeks. If fresh tips burn again after you resume feeding, the medium still holds salts or the dose is too high. Flush once more and cut the strength by another 25 percent.
Prevention
- Feed to 10 to 20 percent runoff in coco and rockwool so salts cannot stack
- Log input EC weekly and compare it to the feed chart for the plant stage
- Run plain pH-adjusted water between feedings once per week
- Avoid combining additives that both carry nitrogen or calcium
- Mix dry amendments at the labeled rate and never top-dress a wet pot twice