Water issues — either too much or too little — are the leading reason behind yellow leaves. In overly wet soil, roots can't breathe. They suffocate, shut down and stop delivering the water and nutrients plants need. Underwatering, or drought, has a similar effect.

Can yellow leaves turn green again?

Yellow leaves are often a sign of stress, and it's generally not possible for yellow leaves to turn green again. Poor watering and lighting are the most common reasons, but fertilizer problems, pests, disease, acclimatization, temperature extremes, or transplant shock are other potential causes.

Why are my shrubs turning yellow and dying?

Overwatering

Watering issues are generally the most common cause of yellowing leaves. When your plants are overwatered, the performance and vigor decrease. Oxygen is being pushed out of the soil, and the roots are simply “under aired” and suffocating. With little air, the roots will begin to drown and rot.