Why Are My Tomato Leaves Turning Brown?
A brown tomato leaf may have dried from its edge or developed separate lesions that later joined together. Trace where the damage began before treating the entire plant for blight.
Concentric Rings Are a Clue, Not a Final Diagnosis
Target-like lesions on older tomato leaves support an early-blight investigation, while small numerous spots or water-soaked patches suggest other possibilities. Look at stems and fruit as well as leaves. Rapidly spreading disease after favorable weather deserves local confirmation rather than reliance on color alone.
| What you see | Most likely clue | What to check next |
|---|---|---|
| Lower leaves with dark spots and yellow halos | Early blight likely | Remove affected leaves and improve airflow |
| Brown, crispy edges in hot weather | Drought or heat stress | Check soil moisture and mulch |
| Sudden edge burn after feeding | Fertilizer burn | Flush soil and pause feeding |
| Only oldest shaded leaves affected | Natural aging | Prune lightly and watch new growth |
Before spraying or fertilizing, check where the browning begins, whether spots are round or irregular, and whether the damage is dry and crispy or soft and collapsing. Use the table below for a fast first pass.
Early blight or other leaf disease
Tomato leaves that develop brown lesions—especially low on the plant—are often dealing with early blight or a similar fungal disease. Remove the worst leaves, avoid wetting foliage late in the day, and increase spacing or pruning so leaves dry more quickly.
Inconsistent watering
When the soil cycles from very dry to very wet, roots struggle and leaf edges can brown. Water deeply instead of lightly, then allow the top layer to begin drying before watering again. Mulch helps even out the swings.
Fertilizer or salt buildup
Too much fertilizer can scorch roots and show up as browned margins. If you recently fed heavily, water thoroughly to leach excess salts and avoid feeding again until the plant stabilizes.
Heat, wind, or sun exposure
During extreme weather, older leaves may brown from environmental stress. Make sure the plant is evenly watered and protected from reflected heat if it is growing against a wall or in a very hot container.
Remove badly damaged leaves, correct watering, and avoid crowding. Judge recovery by the condition of new leaves, not by waiting for brown tissue to turn green again.
Protect Fruit When Removing Lower Foliage
Remove severely affected leaves selectively and keep cuts clear of healthy stems. Heavy defoliation can expose tomatoes to sunscald. If only old lower leaves are declining, compare them with vigorous upper growth before interpreting the whole canopy as diseased.
