by Nebula Haze
Are your leaves all tipped up, “praying” to the sun gods? Leaves pointing up is usually the sign of a healthy, fast-growing marijuana plant that’s getting a lot of light, but in some cases, is accompanied by light stress. Learn how to tell the difference!
Leaves Pointed Up = High Light Levels (usually)
If praying leaves appear on a healthy, fast-growing plant, you probably found the “sweet spot” for light intensity. You’re giving your plants intense light levels, so they grow as fast as possible, yet you know you’re not giving too much because the leaves are green and healthy.
Praying leaves are a good thing if you see them on a green, fast-growing plant
It’s common for indoor growers to “ride the line” and give plants as much light as possible without triggering light stress. Maximizing the light intensity improves growth rates and yields as long as you pay attention if the plant says “enough is enough!” A sick plant doesn’t produce well.
Intense light in the flowering stage helps produce the biggest buds. The pointed-up leaves in this picture are a healthy green color, which means the plants are in the “sweet spot” for light intensity.
As long as leaves are staying green, there’s probably nothing to worry about. Just remember that if leaves are praying for a long time (especially in the flowering stage, or if the air is hot or dry), sometimes they get “overworked” and start turning yellow earlier than you’d like.
Wait, light stress can cause yellowing?
Yellow leaves are often caused by a nutrient deficiency, but if you know the nutrient situation is perfect and observe the praying leaves go from green to yellow, it could be light stress. In that case, you may want to move the lights further away or rotate your plants around to allow the stressed leaves to get more shade. You don’t want your leaves dying early if you can help it.
It’s common for growers to think their plant is suffering from a deficiency when the issue is actually light stress. In that case, the praying leaves are a sign to help you narrow down the cause to your light levels.
Praying leaves aren’t a problem, but you should be concerned if leaves start looking bleached (usually with yellow tips). That means the plant is getting too much light.
This isn’t a nutrient deficiency. These symptoms (leaf edges tipped up, yellowing, yellow tips) are the result of too much light.
What to do if you see light stress
- Don’t panic! If you see a few symptoms on your leaves, it’s not the end of the world. It’s annoying to see yellowing, but we’re here to grow buds, not leaves. It’s rare for any cannabis grower to get to harvest with plants that are entirely green from top to bottom. Remember that the appearance of your leaves won’t matter after harvest.
- Move grow lights further away – It can help to move your grow lights up a bit, but that’s not an option if you’ve run out of height. Learn how to deal with too-tall plants.
- Rotate plants regularly. Try to keep affected leaves as far away from the light as possible and use rotation to give breaks to the hardest-working leaves.
- Angle your grow light so the light hits plants slightly from the side. Light stress is most common when the light is beaming straight down from above. Even a slight angle can reduce light burn (and as a bonus, side lighting can help buds fatten further down into the plant).
- Reduce light power – Certain LEDs and HPS grow lights can dim down the light intensity. A life-saver if you see light stress!
- Bend tall branches away from light using gentle bending or supercropping. Bending may be necessary if your plant grew too close to the light. Tie branches down to secure them, or they’ll try to grow back toward the light!
- Maintain an excellent growing environment – Hot, dry air can make plants more sensitive to intense light, so try to avoid high temperatures and low humidity.
- Avoid nutrient deficiencies – Ensure your plants are getting proper nutrients and the right pH at the roots. Plants can handle more light when they’re getting perfect nutrients/pH. Even if the rest of the plant isn’t showing signs of nutrient deficiencies, the pH being too high or low can potentially make your plant more likely to get stressed by light.
- Get a light-resistant strain if possible (though I understand you’re probably already growing right now, so this tip is more for next time)
In addition to bleaching leaves, too much light can actually bleach the tops of buds!
Sometimes it’s just some plants experiencing symptoms…
I also wanted to add that you may notice only some plants reacting poorly to the lights even if they’re all the same distance away. I’ve especially observed this with certain LED grow lights (I’m looking at you, blurples!). Strains seem to react differently to different LED spectrums and models. But it can happen with other types of grow lights, too. Some strains are more sensitive to light and specific environmental conditions than others.
If a plant’s ancestors originated from the equator, they’re likely more light-loving than a plant that came from a wintry climate. What causes one plant to thrive might cause a different plant to turn yellow.
Your grow light may stress some strains but not others at the same distance. Each plant is a little different.
Remember to check on cannabis plants daily and react quickly to any problems to the best of your ability!
Example of a Light-Stress Resistant Strain
Amnesia Auto by MSNL can take high light intensity like a champ. I’ve grown it under different LEDs, LECs, HPS, and even fluorescents. It tends to grow tall, but never experiences light stress.
This Amnesia Auto got within 10″ of Quantum Board LEDs and didn’t get stressed