May 2013 Newsletter (vol.18)   >>   Tomato Season + BER



Tomato Plant

As the temperature starts to rise and summer is beginning to approach, think about all the fresh vegetables from the garden. The juicy, red, ripe tomato is the fruit of choice that comes to mind not only for home gardeners, but also large farms. If you’re not careful, one thing can take away your favorite summer treat, blossom end rot. Blossom end rot (BER) can be detrimental to the perfect tomatoes you get from the garden. It is not a disease, but instead a physiological disorder caused by a calcium imbalance within the plant. This is caused by a lack of calcium uptake from the soil which is shown in the fruits during dry weather. A plant absorbs calcium through water, but calcium isn’t fast moving. It is most common when the growing season begins wet and then becomes dry.


Tomato Plant


How to identify

  • Blossom end rot is a common tomato problem but can also be found on cucumber, eggplant, pepper, squash and melon fruits.
  • It only affects the fruit, not the leaves or stems.
  • The first symptom of the BER is a slight water soaked area near the blossom end of the fruit.
  • The bottom side of the tomato develops a sunken, leathery dark brown or black spot.
  • The decaying spot can be merely a speck or cover half or more of the tomato.
  • Secondary fungi may inhibit in decaying area.
  • It is more common on staked tomatoes than on bush types and also on the windward side than on the leeward side.
  • More common on the first fruits to ripen.


  • Keep the water supply even throughout the season so that calcium uptake is regular. Tomatoes need 1-3 inches of water a week. They perform best when watered deeply to at least (6 inches) a couple of times a week rather than superficially every day.
  • Maintain soil pH at or near 6.5.
  • Wait to plant until the soil has reached a consistent temperature.
  • In the greenhouse, transplants should not be grown too quickly nor should the plants be too old and subjected to severe hardening before transplanting.
  • Steady growth rate as a seedling and as a field plant will discourage most of this problem.


  • BER can’t be reversed on a tomato once it’s set in, but you can take steps to slow or halt it.
  • Pick the affected fruit to reduce stress on the plant and allow it to direct its energy to other fruit.
  • Use Rot-Stop Tomato Blossom End Rot as a foliar spray to help treat the calcium deficiency in the plant.
  • Use Chick Magic tomato plant food that contains abundant amounts of calcium which will help to treat, if not prevent BER.
  • Use calcium nitrate as a fertilizer that supplies both nitrogen and calcium that is very water soluble so it is easy for the plant to uptake.
  • Cut out spots on harvested fruit and enjoy the remainder. If fungi or mold has set in then discard the whole tomato.

It is also a good rule of thumb to choose tomato varieties that are less prone to BER. Determinate tomato varieties are more prone to BER because they set fruit in a short period of time. Indeterminate varieties and semi-determinates set fruit throughout the season, making it easier for plants to regulate calcium intake. The tomato varieties Jet Star, Better Boy and Early Girl seem to have some tolerance.

You might not have thought that picking tomato plants was so difficult. There are many things to consider when choosing what to put into your garden.  Thankfully, there are many options to prevent and treat blossom end rot so that you can sit back and enjoy your homegrown tomatoes!


“Blossom End Rot”
“Blossom End Rot of Tomatoes”
“Tomato Diseases: Blossom End Rot”
“Blossom End Rot in Tomatoes: Causes & Prevention”