What can I do to keep tomatoes from forming a black spot on the bottom? They look beautiful, then you turn them over and see it. Are the tomatoes safe to eat if you cut the spot out?
The black spot on the bottoms of tomatoes is a condition called blossom end rot. Rodale’s Vegetable Garden Problem Solver provides a concise explanation:
Blossom end rot is usually caused by water stress due to lack of moisture, which hampers the plant’s ability to take up enough calcium from the soil. But it can also be caused by too much water, soil pH that is too acidic or too alkaline, too much nitrogen fertilizer, or other problems. The area first turns tan and leathery, and then other pathogens can invade and cause the rot (it turns black and soft).
Rodale suggests removing any tomatoes that show signs of rot so the plant can put energy into developing new, healthy tomatoes. If the soil is dry, water it well and use mulch to conserve moisture. Throughout the season, keep the soil evenly moist by watering as needed.
At the end of the season, be sure to clean up any fruit that falls to the ground, as it may contain secondary rot organisms. And next year, prepare the bed to encourage the plants to develop good root systems – plant in loose, fertile soil, and check the soil pH to see that it measures above 6.5. Add lime as recommended to raise the pH to 6.5 to 6.8, Rodale suggests.
The experts at Rodale suggest to compost the immature fruit that is beginning to show signs of blossom end rot, because they probably won’t ripen properly anyway, but it also looks like it doesn’t hurt to cut off the spot and use the tomatoes if they’re at a stage that you want to do that. In my experience, once they start to rot, they go quickly, though.
By the way, blossom end rot can also affect peppers, eggplant, squash and melons.
July in the garden: What to do with that bounty of herbs? See the July Garden Calendar at Tennessean.com for herbs information, plus this month’s events, tips and tasks.