Leaves turn yellow for a variety of reasons. One of the most common reasons is that the plant is not getting enough water or nutrients. When a plant is under-watered or nutritionally deficient, the chlorophyll in its leaves begins to break down, which can cause the leaves to turn yellow.

Other factors that can cause leaves to turn yellow include:

  1. Overwatering: If a plant is getting too much water, the roots may begin to rot, which can cause the leaves to turn yellow.
  2. Pests: Certain pests, such as aphids and mites, can feed on the sap of a plant, causing the leaves to turn yellow.
  3. Diseases: Some plant diseases, such as leaf spot and blight, can cause the leaves to turn yellow.
  4. Age: As leaves age, they naturally begin to turn yellow and fall off the plant.
  5. Environmental conditions: Exposure to too much direct sunlight or extreme temperatures can cause the leaves of some plants to turn yellow.

In general, it is important to pay attention to the overall health and well-being of your plants, including ensuring that they are getting enough water, nutrients, and appropriate levels of sunlight. If you notice that your plant's leaves are turning yellow, it is a good idea to try to identify the cause and take appropriate action to address it.