Yellow Leaves on Vegetable Plants: Common Causes
Owen Petrakis · Oct 24, 2026 · 6 min read
Quick answer
Nutrient shortages, watering problems, and disease all cause yellowing. The pattern tells you which.
Yellowing leaves on tomatoes, beans, courgettes, and other crops can be alarming. Sometimes it is natural ageing; sometimes it signals a problem.
Look at which leaves are yellowing and how.
1 Older, lower leaves yellow first
This often means nitrogen shortage, as plants move nitrogen from old leaves to new growth. Feed with a balanced fertiliser. It is also normal for a few lower leaves to yellow as plants mature.
2 Yellow between green veins
Yellowing between veins on older leaves can indicate magnesium deficiency, common in tomatoes fed heavily with potash. On new leaves, it may be iron deficiency, often caused by alkaline soil.
3 Watering problems
- ✓Waterlogged soil starves roots of oxygen, causing yellowing and wilting
- ✓Drought stress causes yellowing and leaf drop
- ✓Containers dry out quickly in summer
4 Disease
Yellow patches that spread, often with brown spots or wilting, can indicate fungal diseases or wilts. Remove affected leaves, improve airflow, and rotate crops.
This is general gardening information. Results depend on your climate, soil, and conditions. Follow label directions for any fertiliser or treatment, and check whether plants are toxic to pets or children before bringing them home.