Tomato blossom end rot


How to stop blossom end rot. Can we use Epsom salts? Live in Etobicoke.


Thanks for asking this question about a popular idea .

Blossom end rot is due to adverse growing conditions and often occurs where fruit develops rapidly when it’s hot and dry – and we’ve had lots of that type of weather this summer .

The ultimate cause  is  calcium deficiency, which – in the fruit itself – disrupts the permeability of the cell membrane, resulting in cell swelling, leakage and ultimately breakdown of membrane. As well, fewer new cells grow. This results in black, sunken areas of the fruit, which is vulnerable to attack by bacteria, fungi and pests.

Even if calcium is present in the soil , the plant cannot take up the nutrient if the soil is too dry , so fluctuations in watering are usually the preventable  cause.

Since magnesium ( which is what Epsom salts is ) competes with calcium uptake , adding it  is not only unnecessary but counterproductive  . (see the University of Saskatchewan’s information on this topic at

Combatting blossom end rot, is all about ensuring that the plant has a consistent source of water and good soil.

Good soil: If you are growing in pots, be aware  there will always be a nutrient deficiency unless there is a fertilizer or compost added. Potting mix isn’t soil and has very few nutrients.Some people put the crushed shell of an egg in the hole at planting time and rotate the location of tomato plants each year .

Watering: Ensure the soil/potting mix is not allowed to dry out between watering  (thus causing  the plant’s roots to  dry out inhibiting calcium uptake ) .Conserve moisture around plant roots by mulching. Apply any fertilizer to moist soil – not to dry soil, as the concentrated nutrients can restrict the plant’s water uptake…and not too much fertilizer .

Finally , please remove the affected tomatoes immediately, to give other fruits the opportunity to develop normally.

Other resources you might find interesting :

Missouri Botanical garden. Tomato diseases and disorders.

Toronto Master Gardeners. Calcium for tomato blossom end rot.

Thanks for raising this . Hope you can soon enjoy some delicious tomatoes free from blossom end rot .