What do you do when nutrient burn hits during flowering?
Stop feeding, flush the growing medium with pH-balanced water, and restart nutrients at half strength once new growth looks clean. Nutrient burn during flowering is a salt buildup problem, not a disease, and most plants recover in one to two weeks when you act at the first crispy tips. The burned leaves you already have will not turn green again, but the flowers can finish with full weight.
cannabis nutrient burn vs light burn how to tell
Nutrient burn happens when roots take in more mineral salts than the plant can use. The excess collects in the medium, pulls water away from the root zone, and pushes potassium, calcium, and magnesium out of reach. Flowering plants are the usual victims because growers raise bloom feed right when the plant's water demand climbs.
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How to tell nutrient burn from other flowering problems
Crispy brown tips on the top leaves, moving down the leaf edge, point to nutrient burn. The damage is dry and even, with no dark spots, slime, or webbing.
- Nutrient burn: brown or bronze tips and edges, leaves curl down like a claw, damage starts at the top of the canopy.
- Light burn: bleached or yellow patches on the tallest colas, often with taco-shaped leaves.
- pH lockout: yellowing between veins, purple stems, spotting across the whole plant.
- Heat stress: leaf edges cup up instead of down, and the whole canopy wilts at midday.
Step by step: fixing nutrient burn in flower
- Check EC and pH first. Measure your runoff or reservoir. Runoff EC far above your input means salts have built up.
- Stop all nutrients. Skip the next one or two feeds. Plain water only.
- Flush the medium. Push pH 6.0 to 6.5 water through the pot until the runoff runs clear and low.
- Measure runoff again. Aim for runoff EC within 0.3 of your target feed strength.
- Wait three to five days. Watch the newest leaves. Green tips mean the plant has stopped burning.
- Restart at half strength. Rebuild to full bloom strength over two or three feeds.
How much water should you flush with?
In soil, run two to three times the pot volume through the medium. A 5-gallon pot gets 10 to 15 gallons of water.
nutrient burn on young plants recovery time
In coco coir, one to two times the pot volume is enough. Coco drains fast and holds fewer salts than peat or compost mixes.
In hydro, skip the top flush. Dump the reservoir, rinse it, and refill with plain water at the right pH for 12 to 24 hours, then add a quarter-strength mix. Salts dissolve in recirculating water, so a full reservoir change beats topping off.
What to feed after the flush
Come back at 50 percent of your previous bloom strength, then step up feed by feed. Most flowering plants in weeks 4 to 6 sit between 1.2 and 1.8 EC in coco or hydro, and lower in amended soil.
- Keep phosphorus and potassium moderate. Bloom boosters are the common trigger for burn in mid-flower.
- Hold calcium and magnesium steady. Excess potassium blocks both, and that shows up as brown spots on new leaves.
- Water to 10 to 20 percent runoff in containers so salts do not stack up again.
- Log every feed. The number that burned your plant is data, not failure.
What not to do
- Do not flush with nutrient solution. It adds back the salt you are trying to remove.
- Do not add another bloom booster to fix stalled buds. Burn slows growth, and more feed slows it more.
- Do not strip every damaged leaf at once. The plant still needs them for the last weeks of photosynthesis.
- Do not harvest early to escape the problem. Burned tips do not spread into buds the way bud rot does.
How long does recovery take?
New growth should look normal in 7 to 14 days. Leaves that already turned brown stay brown until they drop or you trim them at harvest. If tips keep crisping after the flush, your medium still holds salts or your feed strength is still too high.
Will nutrient burn lower your yield?
Mild tip burn costs little. A plant that burns for one week in mid-flower finishes close to the same weight as a healthy sibling. Ongoing burn through weeks 5 to 8 is the costly kind: it cuts bud swell, pushes foxtailing, and can leave a harsher smoke with more leftover salts in the tissue.
Frequently asked questions
Can you reverse nutrient burn on leaves?
No. Damaged leaf tissue does not repair. You reverse the cause by flushing and lowering feed, and the plant replaces the damage with new growth.
Do you need a flushing agent?
Plain pH-balanced water handles most cases. Commercial flushing products can help when salt buildup is heavy, but they are not required.
Does nutrient burn look like light burn?
They look different. Nutrient burn starts at leaf tips and edges with a dry, crisp texture. Light burn hits the top of the canopy with bleached patches and leaves that fold or taco.
Should you flush before harvest if you burned the plant?
A 7 to 10 day plain water flush before harvest is standard in soil and coco. If the plant burned, that flush clears the salt buildup too, so both jobs get handled at once.
What if the burn happened in week 7 or 8?
Cut feed to a light maintenance dose, keep your watering schedule, and let the plant finish. Late-flower burn rarely changes the final product when you stop pushing salts.