Why is the bottom of my tomato ?

by Carol
(Edmonton, AB, Canada)

Q. Why is the bottom of my tomato rotting while the fruit is on the vine?

Tomato Dirt responds ...
A. There are several possible scenarios that could be the culprit.

• Blossom end rot: The bottom side of the tomato (either a green or ripened one) develops a sunken, leathery dark brown or black spot. Gardeners most often notice BER when fruit is 1/3 to 1/2 its full size. It's caused by a calcium imbalance. (Read more.)
  
• Soil contact. As the plant comes into contact with the soil, fungi find it easier to impact all of its parts including the fruit. Take steps to protect your tomato plants. Leave plenty of room for circulation in between plants. If you live in an area that does not have consistently high temperatures, then considering pruning lower suckers (read more about pruning tomatoes.) Mulch around plants (read more about mulching.)
  
• Anthracnose. Look for small, watersoaked, circular, sunken, dark spots under the skin of fruit as it ripens. While BER forms on the blossom end of tomatoes, anthracnose can affect tomatoes on any part of the fruit. Spots can develop jelly-like ooze, splitting with excessive bruising, and soft decay. Maturing and ripe fruit are especially vulnerable to developing anthracnose. The disease is caused by a fungus. Treat plants with a biofungicide like Serenade, beginning just as plants form fruit.