Cannabis Nutrient Burn Fix: The Short Answer
Stop feeding. Flush the growing medium with pH-balanced water at roughly two to three times the volume of the pot, then let it dry back and restart at about half your previous nutrient strength. The burnt tips you already have will never heal, so what you're actually watching for is new growth coming in flat, green, and uncurled.
how to fix cannabis nutrient burn
What Nutrient Burn Actually Looks Like
People usually catch this too late because the first sign is small. I look at the oldest fan leaves first, since those have been sipping the strongest solution the longest.
Cannabis Nutrient Burn in Flowering: What It Is and How to Fix It
- Crispy brown or copper tips, like someone held a lighter to the leaf point
- Leaves clawing downward, stiff instead of springy
- A dark, waxy green that edges toward blue
- Burned margins creeping inward from the edges
- Stalled growth even though the plant looks "healthy and rich"
A plant that's overfed doesn't look starving. It looks overstuffed, and that's the difference worth memorizing.
cannabis nutrient burn in flowering
Step 1: Confirm It's Actually Nutrient Burn
Several problems wear the same costume. Light burn hits only the top canopy, closest to the lamp. Potassium deficiency yellows between the veins before the edges go brown. Wind burn from an oscillating fan looks tattered and dry but stays green. pH drift locks nutrients out and mimics a deficiency even when you're feeding plenty.
The cheapest test is your runoff. Measure the EC or PPM going in and coming out. If runoff reads noticeably higher than your input, salts are piling up in the medium faster than the plant can drink them. That's nutrient burn, or the salt buildup that leads straight into it.
Step 2: Flush the Medium
Flushing is just watering to heavy runoff with plain, pH-corrected water. No nutrients in the first pass.
- Set your water to the right pH for your medium, roughly 6.0 to 6.8 in soil and 5.8 to 6.2 in coco.
- Pour slowly in stages, letting the pot drain between rounds.
- Aim for two to three times the pot volume in total water. A 5-gallon pot gets 10 to 15 gallons.
- Measure the runoff at the start and the end. You want the number dropping toward your input level.
- Stop once runoff EC comes down near your target. Over-flushing strips everything and leaves the plant starving in wet soil.
In hydro or coco with a reservoir, dump the res, run fresh pH'd water through the system for a day, then mix a mild batch. In living soil, be gentler: a heavy flush wrecks the microbial life, so a slow leach with plain water is usually enough.
Step 3: Reset Your Feed Strength
Once the medium has dried back enough to water again, resume feeding at 40 to 50 percent of the strength that caused the burn. Bump it up slowly over the next couple of weeks and only if new growth stays clean. Plants that just got flushed are thirsty for food but bruised, so small, steady doses beat a big correction.
If you were stacking additives on top of a base nutrient line, cut that out. Most nitrogen toxicity cases come from three bottles doing the job of one.
Step 4: Watch New Growth, Not Old Damage
The leaves that burned are done. They'll stay crisp and might crumble off, which is fine. Recovery shows up as fresh growth at the tips of the branches: flat leaves, even color, no clawing. If that new growth still curls after two weeks on a reduced schedule, the problem wasn't overfeeding and you should look at pH, root health, or temperature instead.
Mistakes That Make It Worse
- Adding more nutrients to "balance things out." It doesn't.
- Flushing weekly as a habit. You leach out what the plant needs and create a new deficiency.
- Leaving the pot sitting in runoff. That re-absorbs the salts you just pushed out.
- Flushing into cold, soggy soil and inviting root rot.
- Judging recovery by the burned leaves instead of the new ones.
Preventing the Next Round
Feed to about 10 to 20 percent runoff every time so salts never accumulate in the first place. Keep a log of input EC versus runoff EC, and if the gap widens for two waterings in a row, back off the strength before symptoms show. Match your feed to the plant's stage too: seedlings and late-flowering plants drink far less than a mid-flower plant packing on weight. Finally, check your pH pen now and then. A meter that drifts half a point will cause more problems than any bottle in your cabinet.