How to Fix Yellow Leaves on Pepper Plants:
Peppers hate wet feet, and will start to yellow if their roots are too wet all the time.
Yellowing leaves could also be an indication that the plants could also need nutrients. It's important to use quality well-draining potting soil mix if grown in containers. If you are growing pepper in the ground, we highly recommend mixing in homemade compost into garden beds to provide long-term nutrients. We also find that Seaweed or Kelp fertilizers help naturally improve nutrients in the soil. Peppers are light feeders, but will benefit from a regular feeding of a well-balanced, organic fertilizer or compost tea. Avoid high nitrogen fertilizers. They create lush foliage, but you won't get a lot of peppers.
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Yellow leaves COULD be caused by under-watering, but we find that overwatering is usually the culprit! Make sure to use good well-draining soil with lots of organic matter like compost, and make sure to let the soil dry out between waterings. We also like to mulch our peppers with grass clippings to further add nutrients to the soil over time, and keep the soil more consistently moist.