Preventing Blossom-End Rot in Tomatoes with Epsom Salts and Solarization

The Problem

A gardener asks if she can treat her soil in fall to prevent “dry rot” (blossom-end rot) on next year’s tomatoes.

Two-Pronged Approach

1. Solarize the Soil

Cover the bed with black plastic for 6 months over fall/winter. The trapped solar heat kills many soil-borne pathogens, including fungi that contribute to rot.

2. Supplement Calcium and Magnesium

Blossom-end rot is a calcium deficiency often induced by irregular watering or magnesium shortage. Epsom salts (magnesium sulfate) help the plant uptake calcium and phosphorus.

• At planting: Add 3 tsp Epsom salts per planting hole, scratched in thoroughly to avoid root burn.
• Monthly foliar spray: Dissolve 3 tbsp Epsom salts in 1 gallon water; spray plants once a month after fruit set.

Additional Tips

• Maintain consistent soil moisture with mulch and deep watering.
• Amend soil with compost, peat moss, and aged manure to improve structure and nutrient availability.
• Avoid high-nitrogen fertilizers, which promote foliage over fruit.