Diagnosing Brown Leaves on Tomato Plants: Overwatering vs Sunscald

Introduction

Tomato leaves turning light brown and leathery—without drying out—often point to watering issues rather than sun damage.

Identifying the Cause: Overwatering

Keeping soil constantly moist leaches nutrients and waterlogs roots, preventing oxygen uptake. The first sign is leaf discoloration, followed by reduced blooming.

Proper Watering Technique

• Water only when the top 2 inches of soil are dry.
• In most climates, this means deep watering twice a week (~1.5 inches total).
• Water deeply to encourage downward root growth; shallow watering draws roots up.

Mulching Benefits

Apply 2 inches of straw, dried grass clippings, or shredded leaves around the base to cool soil, retain moisture, and reduce watering frequency.

Soil Amendment

Annually add compost, peat, and manure to improve drainage, tilth, and nutrient availability.

Conclusion

Switch to deep, infrequent watering, mulch heavily, and amend soil yearly to resolve brown leaf issues.