Tomatoes: Rotten Tomatoes

Recently I was asked a question concerning tomatoes which appear to be rotting on the vine. I thought a blog post would be a good way to answer the question as many other people likely have seen this not uncommon problem, or are likely to in the future.

This picture, passed along to me, which is bound to make any gardener a little squeamish, shows the problem which is called Blossom End Rot.

Blossom End Rot on Tomato

Blossom End Rot

The symptoms include a sunken brown or black discoloration at the bottom of the tomato. This particular problem always starts at the blossom end of the tomato, hence it's name. This spot will increase in size with time. It is also very likely that the symptoms will manifest themselves on additional fruit on the same plant and possibly nearby plants as well.

Of the many possible problems a plant can get this one is unique in that it is a physiological problem. It is not caused by insect, bacteria, or fungus. In other words it is not solved by some kind of insecticide or fungicidal spray.  Being physiological, it is not contagious to other plants.

Blossom End Rot is caused by a lack of sufficient calcium during critical stages of fruit development.  Tomatoes get calcium from soil, pulling it in through their roots in solution along with water and other nutrients. Calcium is used by the plant in part to create more complex molecules which hold the cells together.

                                                                                      It's a sad tomato that can't hold it cells together.


CONTROL

Like most problems in life, as in plants, the best control is preventative. In most cases tomatoes don't get enough calcium as a result of dramatic changes in soil moisture levels. Plants whose roots go from really wet to extremely dry are much more likely to get Blossom End Rot. Not enough water in the soil decreases the amounts of calcium taken up by the roots. 

DO:

• Keep your tomatoes evenly moist, especially in times of drought
• Apply a well composted mulch around your plants to keep soil moist for longer periods
• Plant tomatoes in soil that drains well as water logged roots can cause similar problems
• Used a balanced fertilizer if and when needed
• Dispose of all affected fruit on the plant
• In extreme cases spray plants with calcium chloride solution every 10 days
• Keep the soil pH around 6.5 to free up more calcium in the soil. Too high pH ties up calcium

DO NOT:

• Cultivate or break up the soil around the plants roots
• Apply too much fertilizer high in Nitrogen. Too much fertilizer can cause plants to grow rapidly and magnify the calcium deficiency problem as fruit is developing
• Allow plants to dry out too much following periods of rapid growth

Blossom End Rot could be thought of as a tomato's version of tooth decay. Both are caused by calcium deficiencies and are also similar in that, as mentioned above, they are physiological issues. Too bad tomatoes don't drink milk, huh?

Blossom End Rot can also be present in eggplants and sweet peppers. The treatment and preventative measure would be the same as for tomatoes.

If you are seeing other problems with your tomatoes or any other plant you're trying to grow in your garden feel free to share pictures and questions with me and let them be the source for an upcoming blog post.