Epsom salts prevent blossom end rot.
Refuted
Epsom salts won't stop blossom end rot. BER is a calcium-transport problem caused by uneven watering, not a magnesium shortage — and added magnesium competes with calcium uptake. Water evenly, mulch to buffer soil moisture, and soil-test before adding anything.
What is actually known
Blossom end rot is a localized calcium shortage in the fruit, driven by uneven water uptake — calcium rides the transpiration stream, so erratic watering starves the fruit tip even when soil calcium is adequate. It is not a magnesium deficiency. Epsom salts add magnesium, and magnesium competes with calcium for uptake, so they do nothing for BER and can make it slightly worse. The levers are even watering and mulch; get a soil test before adding any nutrient.
Evidence: not yet confirmed against its 1 source.
what this rests on - one pointer
Iowa State University Extension, Yard & Garden, 'Blossom End Rot' (yardandgarden.extension.iastate.edu/encyclopedia/blossom-end-rot, read 2026-07-14): 'This is a problem born of calcium deficiency, most often the result of erratic watering'; 'Adding calcium to the soil is generally ineffective.' Confirms BER is a calcium-transport / water-management disorder, not a magnesium shortage — so Epsom salts (magnesium) cannot address it.
When would that grow at your place? →