What is causing the blossom end rot in this particular method of tomato growing? I've never encountered this in my upright tomatoes. I water it every other day. My neighbor's hanging tomatoes do not have this problem.
Topsy Turvy Tomato Plant
Certified GKH Gardening Expert
It is caused by a lack of calcium getting into the plant. It is possible that the potting soil is lacking calcium. Add some Epsom salt. It does not add too much calcium, but it may be enough for a potted plant. Also, start watering every day. With the plant in fruit, it needs more water.