Blossom-End Rot: Causes, Control & Prevention for Tomatoes

Blossom-end rot appears as a sunken, black or leathery brown spot on the bottom of tomatoes, peppers, eggplant, and squash. It's not a pathogen but a physiological disorder caused by calcium deficiency in developing fruit—often triggered by fluctuating soil moisture, which impairs calcium uptake.

Contributing Factors

• Wide moisture swings (drought followed by heavy rain)
• Excess nitrogen fertilizer
• High soil salts
• Root damage during cultivation

Early-season fruit is most susceptible. If the affected area is small, cut it off and eat the rest.

Identification

Starts as a small water-soaked depression on the blossom end of green or ripening fruit. Expands into a sunken, dark, leathery patch.

Control

• Remove affected fruit—plant may set normal fruit afterward.
• Apply liquid calcium fertilizer after removal.

Prevention

• Soil prep: Maintain pH ~6.5. Add lime, crushed eggshells, gypsum, or bone meal to planting holes.
• Consistent moisture: Mulch and/or irrigate for ~1 inch/week. Ensure drainage in wet periods.
• Protect roots: Avoid cultivating near plants.
• Fertilizer choice: Use nitrate nitrogen, not ammoniacal (worsens rot).
• Moderate early feeding: Avoid over-fertilizing during initial fruit set.
• Stake early: Reduces root disturbance.

Plants Affected

• Tomatoes
• Bell Peppers
• Eggplant
• Squash & Zucchini