From our veggie expert:
Remove affected fruit. Don't overdue the N fertilization. Add one 1/4 cup of gypsum (calcium sulfate) per container and water it in.
Blossom end rot is a response to a variety of plant stressors, not just low available calcium and inadequate water. Plants could be space-stressed. Most varieties need at least a 5-gallon container. Some patio and container-type tomato varieties can be grown in 3 gallon containers.

From the Extension website on tomatoes:
https://extension.umd.edu/resources/yard-garden/vegetables/tomatoes/

From me, just to check:
1. Be sure size of container is adequate
2. The container needs drainage holes
3. The container should have been filled with new potting soil mix at the start of the season (after cleaning the container of old soil and washing it with soap and water or dilute bleach to kill any diseases in the old soil)
4, Grow tomatoes varieties suitable to the container's size and plant deeply to develop more roots from buried stem
5. Water only if dry to the touch at 4" soil depth. Watering too often leads to poor root growth and other problems
6. Add calcium as discussed above; I use a handful of agricultural lime when I plant
7. Add fertilizer if you did not start with new soil mix this year and have not added any this year; follow label directions
8. Remove lower leaves (up to 1ft on stem) if yellowing.

Your plants should recover and produce fruit.

Good luck
Len

Thank you very much!



You can get gypsum for gardening in most hardware stores and nurseries. Just put garden gypsum into your browser and see what's convenient. You probably do not need a huge amount and be sure to read the label. 

Insofar as transplanting, you do not say what type of tomato you're growing or the size of your current container. I assume it's 3 gallons or larger. If patio or determinate type (e.g. plum), a smaller container is likely ok. Transplanting a larger plant at this time can be damaging unless it's in a really small (1 gallon) container. If it is 1 gallon, carefully transplant and add new potting soil to the larger container (holes open on bottom).  Just keep checking moisture and fertilizer needs and expect a smaller yield if the container is too small for a larger size tomato. Read about suckers and watch a video or two first.

I appreciate your fast response. Thank you!



Take a look at the MoCo MG Website. The MG Newsletter lists educational opportunities; some may be of interest to you although the Newsletter is mainly for MGs. Also, there are several local demo gardens, special educational days for the public, as well as plant clinics. Many activities are at no cost. The Historic Agricultural Farm in Derwood is where many public events are held,

Montgomery County MG (google.com)

Len

Good morning Len,



look good!
Len