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yellow leaves on marijuana plants outdoors

The roll of chlorophyll is to absorb sunlight and transform it into energy via a process called photosynthesis. When plants have ample access to resources, chlorophyll thrives. When plants are stressed, however, the chlorophyll begins to degrade revealing the yellow carotenoids below.

If the yellowing occurs primarily at the base of the plant, the issue is likely a nutrient deficiency. The most common nutrient deficiency in cannabis is nitrogen, though note that excessive nitrogen can also cause yellowing (plus curled, claw-like leaves). If the problem is caused by a deficiency, slowly increase the concentration of your cannabis-specific fertilizer until new growth appears. If the yellowing is caused by excessive nutrients, flush the root system with pure water then add a half-dose of your fertilizer instead. Magnesium deficiency, characterized by a yellowing around the leave’s green veins, is most commonly caused by an improper pH balance. Use magnesium supplements to correct this issue
If your marijuana leaves are turning yellow, don’t panic! This is just your plants’ way of telling you something is wrong. It is up to you to determine what that is so you can treat the problem without making it worse.

Note that carotenoids cannot directly transform light into energy via the photosynthetic pathway and must pass it onto chlorophyll to finish the job. Therefore, while a minor yellowing leaves will not stop photosynthesis, excessive or unaddressed yellowing can either stunt plant growth or kill the whole thing entirely.
Temperatures outside of the ideal range of 70 to 80 degrees Fahrenheit also risk discoloration and curl leaves. These oddities are most common in leaves toward the top of the plant and can easily be remedied with a fan (if too hot) or root insulation (if too cold). We also recommend growing plants off a cold cement or tile floor; use a milk crate or stool to raise them off the ground when necessary.
Growing your own marijuana is very rewarding, but it can be really nerve wracking, too, especially when those bright green leaves start turning a worrisome yellow. If your cannabis leaves are turning yellow, use these steps to stop the yellowing before it’s too late.
If your yellow leaves come with spots or bite marks, they’re probably infested with pests. Though you can often see the infestation, this is not always the case – a tell-tail sign (aside from the remnants of the buffet) is a plant that lacks vigor in addition to other symptoms associated with things like overwatering or poor air circulation.
If you notice yellowing toward the top of the plant (specifically, nearest the light source), your plants are likely suffering from light burn. Light burn can happen in temperature-controlled environments as easily as those in high-heat if the leaves get too close to the lights. We liken this to getting a sunburn on the ski slopes.

After measuring and adjusting pH, take a look at your watering schedule. The most common cause of yellow leaves is either over- or under-watering. Plants that are over-watered will have leaves that seem swollen and droopy while under-watered plants (though much less common) will be thin and frail. Poor drainage can also contribute to overwatering so always grow your cannabis in pots with drain holes.

Does your cannabis grow have plants with yellow leaves? Yellowing marijuana leaves can indicate a variety of common ailments. Keep reading to learn more about cannabis plant health and tips to overcome yellow leaves.

Yellow leaves on marijuana plants outdoors

Hard or Soft water

Soil
Hard or Soft water – Image powered by Fullhealthsecrets.com

Fungal pathogens cause leaf septoria. These pathogens are brought about by warm weather and rain. More specifically, it targets cannabis plants grown outdoors.

  • Newer leaves turn yellow, orange, or red
  • Leaves turn fragile and slim
  • Woody stems will keep getting taller, and the plant won’t expand
  • Buds may start to die, and the plant’s growth will be stalled in the flowering stage

Iron facilitates the production of chlorophyll – the green pigment that absorbs light and works with carbon dioxide to make plant food.
Plants Will Not Flower
Fusarium

by Bonza · Published February 24, 2018 · Updated January 29, 2020

Cultivating cannabis is fun. For some people, growing itself adds to the experience of its use. Hence, in this article, we cover most of the likely problems cannabis growers may experience.