What causes the dark rings around the ripened stem end of tomatoes?
They are about and 1/8" to 1/4" in diameter and are very black
Certified GKH Gardening Expert
Can you include a photo? This can be a bit of an issue if it is the stem end. The bottom end is a different problem and very easy to correct. The top rotting can be many different things depending on how the damage appears.
If you can include a photo I will be able to better assist you.