Nutrient burn is the easiest cannabis problem to fix and the easiest to misread. The fix: stop feeding, flush the growing medium with pH-balanced water until the runoff EC or PPM drops back near your target, let the pot dry back, then restart nutrients at roughly half strength. Leaves that already crisped up will not turn green again. You are reading new growth from here on, not the damaged fans.
Preventing Cannabis Nutrient Burn With a Feeding Schedule
What nutrient burn actually looks like
Start at the tips and work inward. Classic burn shows as brown, brittle points on the upper and middle leaves, often with a dark waxy green behind them and edges that curl upward. If you are in late flower and running heavy bloom boosters, the tips may look singed while the rest of the leaf stays healthy.
preventing cannabis nutrient burn with feeding schedule
Do not confuse it with three neighbors:
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- Potassium deficiency: brown edges on older, lower leaves, usually with yellowing around the necrosis.
- Light burn: damage concentrated on the topmost colas closest to the fixture, with bleached or papery patches rather than tip burn.
- pH lockout: symptoms spread across multiple nutrients at once and hit the whole plant, not just the tips.
Step 1: Stop feeding and check your runoff
Before you do anything, measure. Water one pot to runoff, catch it, and test EC and pH. In coco and hydro, a runoff EC more than about 0.4 above what you poured in is a clear sign of salt buildup. Soil is harder to read this way, but a runoff EC that climbs week after week tells the same story.
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Rough targets for feed strength: seedlings and clones around 0.4 to 0.6 EC, veg around 1.0 to 1.4, and flower between 1.4 and 2.0 in coco or hydro. If your runoff is well above those numbers, the flush is the right move.
Step 2: Flush the medium
- pH your water first. Aim for 6.0 to 6.5 in soil, 5.8 to 6.0 in coco, and 5.5 to 6.0 in hydro.
- Push through roughly two to three times the volume of the pot. A 5-gallon pot gets 10 to 15 gallons, poured slowly.
- Do it in one session, not spread over days. You want the salts carried out the bottom.
- Catch the final runoff and test it. When EC lands within about 0.2 of your input water, you are done.
Skip any "flushing agent" you saw advertised. pH-balanced water does the job, and you already know what is in it.
Step 3: Dry back, then feed light
Let the pot dry until it feels noticeably light, which usually takes two to four days in soil and faster in coco. Then resume at 50 percent of your previous strength and hold pH in range. Watch new leaves for the next five to seven days. If tips stay clean, step the feed up in small increments, about 10 percent at a time, every couple of waterings.
If the tips scorch again at half strength, your plant simply wants less food than the schedule said. Trust the plant over the chart.
Nutrient burn in soil vs coco vs hydro
Soil holds salts and releases them slowly, so burn there tends to build over weeks and recovers over weeks. Coco is quicker in both directions, and a flush can turn things around in days. Hydro is fastest of all. In recirculating systems, dump the reservoir, rinse it, and mix a fresh batch at half strength rather than trying to dilute what is already in there. A plant sitting in burned solution keeps taking up salts the whole time.
How to keep it from happening again
- Calibrate your EC and pH pens monthly. Drift is the quiet cause behind a lot of overfeeding.
- Check runoff every week or two, not only when something looks wrong.
- Treat tip burn as an early warning and back off 10 to 20 percent before it spreads.
- Be careful when you stack bloom boosters, PK additives, and calmag. Each one adds to the total, and the totals add up fast.
- Keep notes on strength and runoff so you can compare runs instead of guessing.
One more thing worth saying: burned tips on a couple of fan leaves during a strong flower run are not a crisis. Plants push through it. What hurts a harvest is panicking, dumping the reservoir, and swinging the plant from overfed to starved in a single day. Flush, reset, feed light, and give it a week to answer.