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Tomato Woes: Blossom End Rot

Tomato Woes: Blossom End Rot

It happened again...Blossom End Rot on my tomatoes. Thankfully, it's just hitting one container right now. It's a pretty common problem in the garden and I've gotten hit with it before.

What is Blossom End Rot & What Causes it?

Blossom End Rot. Sounds like something we were warned about in high school health class that would result from "risky" behavior. Thankfully though, Blossom End Rot is not something that occurs in humans. Blossom End Rot is a fruit disorder that appears as a dark spot at the end of the fruit and is caused by lack of calcium in the soil or the plant's inability to absorb calcium. Tomatoes need calcium to be delivered through the roots as the fruit starts to develop. Calcium even helps other nutrients get delivered to make the plant stronger. That dark spot often occurs at the beginning of the growing season and can engulf the fruit and turn an otherwise good edible bad. 

Blossom End Rot impacts more than just tomatoes. Plants like peppers, cucumbers, eggplant, melons, squash and other vegetables that produce fruit can also be affected. There are various factors that can prevent a plant from absorbing enough calcium - from soil that is too wet or too dry, an imbalance of pH, damage to the plant or too much nitrogen in the soil. 

How to Prevent Blossom End Rot

I know that calcium is important for tomatoes, so I've been adding ground-up eggshells to the soil - from the time I planted them and every few weeks after that. I also added Blood Meal to the soil, which may have created a situation with the soil being too high in nitrogen. Too much nitrogen can reduce the plant's ability to take in an adequate amount of calcium. There are several different kinds of nitrogen and they don't all have the same impact on plants - I'll do a future post about that. 

To reduce the potential for Blossom End Rot, according to Clemson University Extension:

  • After transplanting seedlings to the garden, keep the plants a little bit on the dry side for the first few weeks. This can help encourage a large root system, which is better able to take in the calcium it needs.
  • Keep the soil moisture consistent.
  • Keep the pH around 6.5.
  • Don't over-fertilize. High-nitrogen fertilizer should be avoided as it can cause problems with the intake of calcium. (Oops.)
  • Apply a layer of mulch to help maintain moisture and keep the soil cooler.
  • Don't cultivate closer than 1 foot to plants to avoid damaging roots. 

How to Treat Blossom End Rot

In my experience, the best treatment has been to remove the affected fruit from the plant immediately and apply Mag-i-cal (also found under the name Cal-Mag) to the soil, which is a highly soluble form of calcium and magnesium. I broke up the soil around the base of the plants and added a bit of this and then watered thoroughly. I've seen suggestions to spray the plants with a calcium chloride solution, but I've also read reports that the plant can't absorb enough this way. Most recommendations are for treating the soil as a way to reduce or prevent the issue, so that's what I'm doing. I'm still finding the spots appear on a tomato or two, particularly the San Marzanos, but it's just been recently treated, so I'll keep an eye on it and keep treating as needed.

What have you found to be the best prevention/treatment of Blossom End Rot?

Eggshell Tip: When you use eggs, wash and dry the shells and save them. Grind them up in a spice/coffee grinder or food processor for use in the garden. The shells contain good amounts of calcium. Typically, I add them to the holes I plant my tomato transplants in and then periodically throughout the season. They also make good slug stoppers by putting egg shells that are only sharply broken - the slugs don't like to cross the sharp edges.
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