Core buying advice: When marijuana leaves show burned tips, dark waxy green color, or clawing, adjust EC for marijuana nutrient burn by lowering the reservoir to 70 to 80 percent of its current strength, then measure input and runoff with a calibrated meter. Buy a temperature-compensating EC pen with 0.01 mS/cm resolution, fresh calibration solution, a pH pen, and a nutrient line with a clear EC-based dilution chart. The meter and calibration fluid matter more than the nutrient brand.
Preventing Cannabis Nutrient Burn With a Feeding Schedule
Why EC Is the Number to Adjust First
EC, or electrical conductivity, estimates the total dissolved salts in your feed. Nutrient burn is a salt stress symptom. Adding more nutrients makes it worse. Before you buy additives or a flush product, confirm that your meter reads the same as a fresh calibration standard. If the reading is off by more than 0.1 mS/cm, recalibrate or replace the pen. A meter that drifts will cause you to chase a problem you cannot see.
Nutrient Burn During Flowering: What to Do
What to Look For When Buying an EC Meter
- Temperature compensation (ATC) that covers 5 to 50 C or 41 to 122 F.
- Two-point calibration, typically 1.413 and 12.88 mS/cm, or 1413 and 12880 µS/cm.
- Resolution of 0.01 mS/cm in the low range. A 0.1 resolution pen is too coarse for seedlings and low-strength feeds.
- Accuracy of plus or minus 2 percent of full scale or better.
- Waterproof housing and a replaceable probe. A dried-out probe is a dead probe.
- Auto-off and hold functions. These save batteries and make runoff testing less messy.
- A storage cap that holds KCl solution. Store the probe wet, not dry.
For runoff checks, a pen with a slim probe or a sampling cup works better than a bulky truncheon. For large reservoirs, a truncheon with a long stem is easier to read. Buy calibration solution in the same scale your meter uses, and check the expiration date. Old calibration fluid is a common source of bad readings.
Nutrients and Flush Supplies That Support EC Control
Choose a nutrient line that lists doses in EC or mS/cm, not only in milliliters per gallon. A line with separate grow, bloom, and micro parts lets you lower strength without changing the ratio. Chelated micronutrients stay available at low EC. A pH adjuster is not optional; EC and pH move together. For flush days, use pH-adjusted water at 0.2 to 0.4 mS/cm rather than pure reverse osmosis water, which can strip the root zone.
nutrient burn on young plants recovery time
Parameter Bands for Cannabis
Use these bands as starting points, then adjust for your cultivar, light intensity, and media. Measure input EC, runoff EC, and pH at the same time.
- Seedlings and rooted clones: 0.4 to 0.8 mS/cm.
- Early veg: 0.8 to 1.2 mS/cm.
- Active veg: 1.2 to 1.8 mS/cm.
- Early flower: 1.6 to 2.0 mS/cm.
- Peak flower: 1.8 to 2.4 mS/cm.
- Late flower and ripening: 0.8 to 1.4 mS/cm.
- Runoff target: within 0.3 mS/cm of input. If runoff is 0.5 mS/cm or more above input, flush and retest.
These numbers assume a soilless or coco mix. In rich living soil, EC readings are less useful because organic nutrients are not fully ionic. In deep water culture, keep the reservoir within 0.2 mS/cm of your target and check daily.
Step-by-Step Adjustment After Nutrient Burn
- Calibrate the EC pen and pH pen.
- Measure input EC and pH. Record the values.
- Measure runoff EC and pH from several plants, not just the worst one.
- Lower the reservoir EC by 20 to 30 percent. Do not change the nutrient ratio.
- If runoff EC is 0.5 mS/cm or more above input, flush with pH-adjusted water at 0.2 to 0.4 mS/cm until runoff drops near input.
- Feed at the lower EC for 3 to 5 days. Watch new growth, not old damaged leaves.
- Raise EC by 0.1 to 0.2 mS/cm per week only if new leaves stay flat and green.
Common Pitfalls
- Comparing EC to PPM without checking the scale. A 500 scale and a 700 scale give different PPM numbers for the same solution.
- Using a meter that reads only 0.1 mS/cm for low-strength feeds. The error is too large.
- Measuring a cold solution. Let the sample reach room temperature or use ATC.
- Mixing nutrients in the wrong order, such as adding calmag after a phosphate bloom booster. Follow the label order.
- Flushing with pure water and no minerals. This can cause a lockout that looks like nutrient burn.
- Chasing leaf symptoms without checking pH. A pH swing can mimic nutrient burn.
- Storing the probe dry or in tap water. Use KCl storage solution.
FAQ
Should I flush with plain water after nutrient burn?
Use pH-adjusted water with a small amount of base nutrients, around 0.2 to 0.4 mS/cm. Pure water can shock roots and strip micronutrients. Run it through the container until runoff EC comes close to input, then resume a lower-strength feed.
How often should I calibrate an EC pen?
Calibrate every 2 to 4 weeks, before a critical runoff test, and after replacing the probe or battery. Rinse the probe with distilled water between standards and let it stabilize before pressing hold.
Can I use tap water for mixing nutrients?
Yes, but measure the tap EC first. If tap water starts at 0.4 mS/cm, your nutrient ceiling is lower. High tap EC can hide salt buildup and make nutrient burn worse.
Does nutrient burn go away?
Damaged leaf tips will not heal. New growth should look normal within 5 to 10 days after you lower EC and correct runoff. If new leaves still burn, check pH, root health, and light distance.
Is EC the same as PPM?
No. PPM is calculated from EC using a scale factor. A 1.0 mS/cm solution reads about 500 PPM on a 500 scale and about 700 PPM on a 700 scale. Use EC to avoid confusion.