Tomato Disease Prevention & Cure: Blossom End Rot

Beginning and mid stages of Blossom End Rot

Beginning and mid stages of Blossom End Rot

Re:  Growing Tomatoes in Containers

Growing tomatoes in containers and pots is a great solution if you are in need of space or have limited areas with sun.  Container growing does have its trials and tribulations however, and sometimes it is a little trickier to get high yields of beautiful tomatoes growing in pots than if you were growing in the garden.

Blossom End Rot is one disease that tomatoes are more susceptible to when grown in pots.  Blossom end rot is initially a light tan, flattened area on the blossom end of the tomato that then enlarges and turns black and leathery.  It is caused by a localized calcium deficiency in the developing fruit.  This calcium deficiency is usually caused by an inconsistent watering regime, i.e., a dry-wet-dry cycle of watering.  Tomato plants prefer about one inch of water per week, and if you allow them to get quite dry in the pots, and then deluge them with water when you notice wilting, you are setting yourself up for blossom end rot.



  1. Blossom End Rot on Tomatoes

    Blossom End Rot on Tomatoes

    Mulch the soil around the plant ro reduce moisture fluctuations;

  2. When rainfall is less than 1 inch per week, soak the soil slowly with water from a hose or set up a soaker hose (sprinklers or watering from above can splash soil onto the plant’s leaves and promote other diseases);
  3. If you grow in pots each year, make sure and use fresh soil each year;
  4. Select disease resistant varieties of tomatoes, and consider growing determinate tomatoes.  Determinate tomatoes are shorter and bushier than indeterminate and they do not continue growing until frost, so they do not vine and outgrow the trellis or stakes you may have in your pots.  With determinates you will get a lot of tomatoes over a 3 to 4 week period rather than fewer tomatoes over a longer period (all summer) as with indeterminates.  Most heirloom varieties are indeterminate, but a few examples of determinate heirloom varieties that grow well in pots are:  Raspberry Lyanna, Manitoba, Principe Borghese, Prescott, and Black Sea Man.  My favorite determinate “hybrid” tomato for pots is the Bush Champion.  It was bred for pots and it is a medium slicing tomato with good flavor.  You can certainly grow indeterminate tomatoes (heirloom or hybrid) in pots, they are just higher maintenance;
  5. Select plastic or fiberglass pots rather than clay pots.  Clay pots dry out too fast and it is harder to regulate the water regime.  A self-watering container, EarthBox 1010039 Organic EarthBox, Terracotta, or home-made wicking system is even better.


Wide range of healthy heirloom tomatoes

Wide range of healthy heirloom tomatoes

All is not lost if your first flush of tomatoes has Blossom End Rot.  It is not a disease that lives in the soil like blight so it is certainly possible to save the remaining tomatoes.  Follow these steps and you can still enjoy a large harvest for the remaining part of summer:

  1. Set up a soaker hose system, transplant to a self-watering container, or be very conscientious about seeing that the pot does not dry out to less than 1 inch of water a week (and water the soil, not the leaves if using a hose or watering can);
  2. Add 2 Tbsp. Epsom salts to a gallon of water and use this to water with every other week.  Epsom salts in the watering regime will replace the calcium that has leeched out of the pot from too much previous watering.

So, to sum up:  water management and Calcium replacement are the two primary factors to be aware of in preventing and curing Blossom End Rot on tomatoes.  Have you had any varieties of heirloom tomatoes that seemed to be more or less susceptible to Blossom End Rot?  I’d be interested in hearing your experiences!

Happy Trails,



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7 Responses to Tomato Disease Prevention & Cure: Blossom End Rot

  1. DDD at #

    Please… from a Chemical Engineer: Epsom Salts contain Magnesium which is beneficial to plants.. but it does not provide Calcium.

    • Thank you DDD for clarifying that. I trust your knowledge over mine on this. I can’t remember the sources where I got this information, but I know it was more than one source. Now I’ll have to research to see if it is the magnesium which helps prevent blossom end rot, or if Epsom salts as a preventive cure is just folklore.

  2. I just threw away four enormous tomato plants due to blossom end rot. I planted Russian black krim heirloom tomatoes, which I love, in plastic pots. Unfortunately, with our hot, humid Maryland summers, they dry out quickly in the pots. The plants thrived and had lots of fruit, but they were riddled with blossom end rot. I tried adding calcium (Tums, eggshells, special sprays, calcium products, etc.), to no avail. I picked off the damaged fruit early on, added mulch over the soil, and so on. Nothing helped. The fruit continued rotting on the vine, so I finally gave up last night and chopped them down. This has happened for several years now. I’m wondering if I would have better luck using wooden containers instead of plastic. Ideas?

  3. pistol pete at #

    thank you, i think many gardens don’t realize the importance of mulch, again i see that word over and over again. fundamentals WATER RETENTION, i do believe i have a calcium deficiency as well, thanks for the site

    • Certainly Pistol Pete. I hope it helped a bit. The next post will deal with late blight. Hopefully you don’t have that problem, but so many heirlooms get it that I thought I’d try to address it. Thanks for the comment!

  4. Certainly Carol! It gives me a lot of satisfaction to know I may have helped someone out, no matter how small. Thanks for commenting


  1. Growing Heirloom Tomatoes in Pots: Best Heirloom Varieties & Growing Tips | Tomato HeadquartersTomato Headquarters -

    [...] are likely to have problems with the potting mix drying out, which can lead to blossom end rot (see this post to help with blossom end rot).  The larger indeterminate heirloom tomatoes will grow well in 12-18 [...]

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