The Q&A Archives: Black rot at the bottom of tomatoes planted in pots on my deck

Question: I planted one Early Girl and one Better Boy tomato in pots on my condo deck. The plants were bought at Home Depot. They look great and I have many tomatoes but they are all turning black on the bottom. Help please.

Answer: What you describe is blossom end rot. It is not a disease, but a physiological disorder of tomato that can appear on fruits at any time in their development, but most commonly appears when fruits are one-third to one-half grown. The initial symptoms are water-soaked spots on the blossom end of the fruit. These spots later enlarge and become black. Secondary infection by other decay causing organisms usually follows. The cause of this disorder is considered to be calcium deficiency in the developing fruit. Extreme fluctuations in moisture, root pruning and excessive nitrogen fertilization can also result in blossom end rot. Best means of control is to maintain a uniform supply of moisture through regular irrigation and with soil mulches. Some gardeners report success with calcium chloride, a preventative spray you can purchase at garden centers. You can't save the affected tomatoes but you can try to stop the disorder from affecting other fruit by maintaining constant soil moisture.

Good luck with your plants!

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