Light burn is bleaching and yellowing on the leaves and buds sitting closest to your grow light. The tops fade to pale yellow or white while the rest of the plant stays green. Fix it by raising the fixture, dimming the output, or widening the gap between canopy and bulb so intensity drops to a safe level.
Why the tops bleach out
When light intensity exceeds what a leaf can process, the tissue closest to the source loses chlorophyll and pales. Unlike a deficiency, this damage is concentrated exactly where the light is strongest, so it maps to distance from the bulb rather than to old or new growth. Modern high-output LEDs make this easy to trigger because growers hang them close and run them hot.
We see it most on the tallest colas that stretched toward the fixture in flower. The buds there can bleach white and lose potency and weight if the problem runs long.
How to identify light burn
Look at the top canopy first. Light-burned leaves turn yellow to nearly white on the tops while lower foliage stays healthy and green. The leaves often stay firm rather than dying off, and the yellowing follows the shape of your light footprint. On buds, bleaching shows as pale, washed-out tops that feel airy. If the fade tracks the brightest zone, it is light, not a nutrient problem.
Light burn versus nutrient issues
This is the confusion we get asked about most, so use the pattern of damage to separate them.
| Sign | Light burn | Nutrient deficiency |
|---|---|---|
| Location | Only the tops nearest the light | Follows old or new growth, plant-wide |
| Color | Bleached yellow to white | Yellowing, spotting, or vein patterns |
| Leaf feel | Often still firm | Can go limp or crispy |
| Fixes with | Raising or dimming the light | Feeding or pH correction |
A true shortage shows a color pattern tied to nutrient mobility, which our cannabis nutrient deficiencies guide breaks down leaf by leaf. If the fade ignores the light footprint and follows old growth, treat it as feeding, not light.
What causes light burn
- The fixture hangs too close to the canopy for its wattage.
- The light runs at full output when the plants are young or freshly rooted.
- Plants stretch in flower and grow into the danger zone without the light being raised.
- Reflective walls concentrate intensity on the outer colas.
How to fix light burn
- Raise the fixture several inches, then check the tops over the next few days.
- If it has a dimmer, lower output rather than only moving it, especially with strong LEDs.
- Confirm your hang height against the manufacturer's recommended distance for your wattage.
- Leave bleached leaves in place unless they are fully dead; the plant still uses partial tissue.
- Keep the room temperature in range, since heat and light stress often show up together.
New growth should come in green once intensity drops. Bleached tissue will not turn green again, so measure recovery by fresh leaves.
How to prevent it
Match light height to growth stage and raise the fixture as plants stretch. Seedlings and freshly rooted clones want gentle light, then you ramp intensity as they build a canopy. A light meter or your manufacturer's chart takes the guesswork out. Because stretch is largest at the flip to flower, plan your hang height around the taller canopy you will have in two weeks, not the one you have today. Our cannabis light schedule for veg and flower covers photoperiod and intensity through each stage, and our cannabis temperature and humidity guide helps you keep heat from stacking on top of light stress.
Recurring problems often trace back to weak or infected stock. Starting from verified, HLVd-tested clones removes a whole class of variables, and hardy beginner strains shrug off most early stress.
Frequently asked questions
Can bleached buds recover?
No. Once a bud bleaches white it will not regain color or potency. Fix the light distance to protect the rest of the plant and any lower buds still developing.
How far should my LED be from the canopy?
It depends on wattage, so follow your fixture's chart. As a rule, stronger lights hang farther, and you raise them as plants stretch in flower. When unsure, start higher and lower gradually while watching the tops.
Is light burn the same as light stress?
They overlap. Light burn is the bleaching from too much intensity, while light stress can also include heat and photoperiod problems. Treat the intensity first, then check temperature and your light cycle.
Why only the top leaves?
Because intensity is highest closest to the bulb. That location clue is exactly what separates light burn from a nutrient issue, which spreads by leaf age instead.
Healthy plants handle strong light better when they start strong. Our freshly rooted, female-guaranteed clones ship nationwide from Colorado and establish quickly under lights. Browse the current cannabis clones for sale and grow from a vigorous base.