Question
I live in Norfolk, Va.  We have 11 tomato plants behind our condo.  They get plenty of sun and water.  We're using miracle grow potting soil.  We have plenty of tomatos on the vine.  The problem is some of the tomatos on different plants are getting brown spots on their bottoms.
We've put lyme into the soil.  It seems to help a bit.  Is there anything else we might try.

Thanks
Mike  

Answer
Mike, your tomatoes are experiencing a condition called blossom-end rot. Blossom-end rot is caused by either a lack of calcium and magnesium in the soil, or by the plant's inability to draw calcium from the soil due to stress. It can also be caused by inconsistent watering, which is very common when growing in containers. The tomatoes are still edible as long as the BER did not spread above the top half of the tomatoes.

During drier conditions, the plants have a more difficult time absorbing nutrients.  Since calcium is normally low in content in most home gardens, the first few tomatoes will experience this problem.  The good news is that it does not spread to other tomatoes and will normally correct itself
after a few weeks.  Even better news is that you can prevent the problem by using corrective measures in early spring.

Epsom salts, composed primarily of magnesium sulfate, has been proven to help prevent blossom-end rot.  Simply mix one or two tablespoons of epsom salts to the soil when planting.  Once the plant begins flowering, apply 1 tbs. epsom salts to one gallon of water and spray liberally on the plants. Then mulch the plants with 3" of straw or dried grass clippings to help retain moisture and keep down weeds. This should be sufficient enough to prevent this problem in the future.

One other trick for established tomatoes is to crush a few Tums and carefully work them into the soil around the plants.  Tums contain calcium and will sometimes serve as a quick solution to BER.

In regards to watering, I recommend watering once every three days if you are receiving average rainfall.  Adjust accordingly if the rainfall varies.  The general rule of thumb is to water to a depth of 1.5" per week for most plants.  Also, never water at night since this can result in fungus diseases.  And mulch heavily to retain moisture.

Finally, do not overfertilize.  Water-soluble fertilizers should never be applied more than once every two weeks.  They are extremely high in nitrogen, which will result in the plant expending all of its energy into producing lush foliage at the expense of blossoming and healthy fruit.

Tomatoes, like all fruit-bearing plants, require a higher concentration of phosphorus and potassium than nitrogen.  There are fertilizer products on the market manufactured specifically for tomatoes.

I personally do not fertilize my tomatoes with synthetic fertilizers. Instead, I amend my soil every spring by adding ample quantites of compost, shredded leaves, aged manure, and peat moss.  These organic supplements increase the fertility of the soil and provide a steady supply of nutrients to the plants throughout the growing season, and they help to balance the PH to neutral levels.  They also help prevent disease and pest problems by improving the overall health of the plants.  When I notice they could use a boost in mid-summer, I apply either fish emulsion or sea
kelp as a supplemental feeding.

Good luck, and please write again if I can ever be of assistance.

Regards,

Mike