Why do my tomatoes rot from the bottom or black spots while on the vine?

It might be blossom end rot from inconsistent watering.

Hi, daddy b!

To elaborate further on what JudyKayTee has stated, are vegetables planted at a proper length from each other so that the roots can develop properly? Do you water your tomatoes during the morning rather than at night? Have you checked to see if their's enough calcium in your soil to support the proper growth of tomato plants? Are your tomato plants properly staked and have enough room to promote the growth of the tomatoes? Have you pruned the "suckers" off the vines of your tomato plants to promote the healthy growth of new fruit?

Those are just some of the things to consider...

Thanks!

Usually if your tomatoes rot on the bottom it is due to a lack of calicum in the soil. There is a product called ( STOP ) that treated blossom-end rot of tomatoes. You should be able to find it at your local home and garden stores.

I agree with the inconsistent water answer, this could be it. Tomatoes also end-rot when the plant is attacked by a variety of fungi referred to commonly as "blight." If your leaves are wilting with black and brown spots on them, this is blight, and can be cured (or at least beaten back) with a spray-on fungicide from your local garden shop.