Lichtstress & Lichtbrand

Light stress & light burn

When Your Cannabis Plants Get Too Much Sun

Light is the engine for your plants' growth. But when growing your three legal plants indoors, more is not always better! Too intense light can lead to light stress and actual light burn. In this guide, you'll learn how to interpret the warning signs and optimize your setup to protect your valuable terpenes.

What is Light Stress in Cannabis Cultivation?

Light stress occurs when the photon density (PPFD) is so high that the plant can no longer process the energy. Photosynthesis essentially "overheats." This happens faster than you might think, especially with powerful LED grow lights, if the distance to the plant tops is too small.

Light Burn vs. Nutrient Deficiency

Caution: Light burn often looks like nitrogen deficiency (yellow leaves). The crucial difference: light burn only affects the uppermost leaves closest to the lamp. A nutrient deficiency usually starts in the lower part of the plant.

Symptoms: How to Recognize Light Burn

Look for these clear signs on the plant tips:

  • Bleached leaves: The leaves turn yellow or even snow-white (chlorophyll destruction).
  • "Praying Leaves": The leaf edges curl upwards to reduce the surface area exposed to light.
  • Burnt tips: The tips appear dried out and brittle.
  • Bud bleaching: The tips of the buds turn white – while this looks interesting, it destroys potency and aroma.

The Solution: How to Avoid Light Damage

To prevent your harvest from burning, you should observe the following points:

  1. Maintain lamp distance: Keep a distance of at least 30–50 cm for strong LEDs. For heat-intensive HPS lamps, even more.
  2. Measure light intensity (DLI): It is crucial to know how much light your plant truly absorbs throughout the day.

    Check out our guide to DLI & light intensity here
  3. Dim instead of full power: In the vegetative phase, 40-60% lamp power is often sufficient. Gradually increase the intensity only during flowering.

First Aid for Acute Light Burn

If your buds are already getting bright:

  • Immediately raise the lamp 10-20 cm higher.
  • Slightly reduce the hours of light or dim the lamp to 70%.
  • Ensure better air circulation to avoid heat stress at the tips.

Your Grow Success Starts Here!

The right genetics are half the battle. Our strains are selected for best results under artificial light.

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Legal Notice: The cultivation of cannabis in Germany (CanG) for adults with up to 3 plants is legal. Ensure the safety of your equipment to avoid fire hazards.

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