Why are my romas perfect on the outside, but have a dark rot in the middle?

by Wendy
(Northern Michigan, USA)

Q. Why are my Romas perfect on the outside, but when cut into the seed core is black with rot?

A. There's at least two possible reasons your tomatoes may look healthy but when you cut into them, they are black and rotted.

1. One form of blossom end rot has no external symptoms, but the interior tomato tissue can blacken and rot. Treat tomato plants in the same way you'd treat any plant with blossom end rot: provide even watering, regular fertilization, and slightly acidic, well-drained soil. (Learn more about blossom end rot).
   
2. Any break in the tomato skin, including tiny holes bored by insects, can let bacteria and fungi into the fruit. The microorganisms can eat away at the interior part of the tomato, leaving black or rotted spots.