A Common Concern
Yellow leaves on tomatoes are alarming but not always a crisis. The key is identifying the pattern and cause so you can take the right action.
Cause 1: Normal Aging
If the lowest leaves turn yellow and drop as the plant grows taller, that is normal. Remove them for better airflow. The rest of the plant should look healthy.
Cause 2: Overwatering
Yellow leaves with consistently wet soil point to overwatering. Roots cannot absorb oxygen. Let soil dry out and adjust watering. Check drainage. See our overwatering guide.
Cause 3: Underwatering
Yellow leaves that are also wilted or crispy indicate underwatering. Water deeply and consistently. Inconsistent watering also causes blossom end rot.
Cause 4: Nitrogen Deficiency
If the whole plant looks pale green to yellow starting from the bottom, nitrogen is likely low. Apply balanced organic fertilizer or fish emulsion.
Cause 5: Disease
Yellow leaves with brown spots may indicate early blight or fusarium wilt. Remove affected leaves promptly. Rotate crops next year and choose resistant varieties.
How to Diagnose
Check soil moisture first. Look at the pattern — lower leaves only or whole plant? Check for spots. Adjust watering, then fertilize if needed. The Personal Harvest Helper app helps identify these issues with personalized guidance.
