Stop Blossom End Rot

Stop Blossom End Rot
You’ve done the dirty work. You’ve raked, dug, and planted. You’ve fertilized and watered and weeded. You’re ready to reap the (literal) fruits of your labors, and harvest some ripe, red tomatoes from your garden. But instead of plump, soft-skinned gems, you find stunted, leathery-bottomed, rapidly shriveling mutants. Ugh!
Blossom End Rot in an Aunt Ruby’s German Green tomato
Blossom End Rot: It ain’t pretty.
You are freaked AF because of the devastating tomato diseases you’ve read about. Like Verticullum Wilt, which would mean no homegrown tomatoes for years while the disease dies down in the soil. Ahhhhh! But it’s Okay. You’re dealing with Blossom End Rot (which I will abbreviate as BER), a condition caused by an inability of your plant to absorb the calcium it needs while setting fruit.

So you’ve got Blossom End Rot

To deal with this problem, you need to understand a few things:
  1. There may be plenty of calcium in your soil, so simply introducing more by adding calcium-rich fertilizers may not help. Also, these calcium sources must break down to be available to your plants, so it would not make a change quickly anyway.
  2. Inconsistent moisture, temperature fluctuations, and other stress when your plant is young and/or setting its fruit can be a major cause.
  3. Over-fertilization or using a fertilizer with too much Nitrogen (The first number in the “N-P-K” trilogy on fertilizer packaging) can make it difficult for your plant to absorb calcium.
  4. Some varieties of plants are terribly prone to Blossom End Rot, and you will likely always find a few of the first fruit of the season suffer for these.
  5. The non-rotted remainder of the affected fruits are still edible.
San Marzano tomatoes, one of my favorites to grow in the Bay Area, consistently produce several stunted and rotted early fruits. Then, usually, for the rest of the season I harvest only large, healthy fruit (and eat lots and lots of fabulous marinara). This year has been particularly bad for BER, as the condition has persisted, on and off, for much of the summer. The extreme heat waves are probably to blame for some of it, and my own overcrowding of my tomato plot will take responsibility for the rest.
A healthy San Marzano next to one suffering from BER.
A healthy San Marzano next to one suffering from BER.
The condition can affect other Nightshades (plants in the tomato family, like peppers and eggplants) as well as squash and cucumbers, and the same factors apply.

What you can do about Blossom End Rot

  1. De-stress your plants. You can’t control the weather, but you can control watering. Try to be as consistent as possible. I swear by a drip irrigation system, and you can get simple ones that attaches to a normal garden hose. Pair that with a timer that runs on batteries, and you’ll never forget to water again.
  2. Fertilize with less Nitrogen. There are even fertilizers made just for tomatoes and fruiting vegetables that should be perfect.
  3. Learn your Varieties. Some just get BER, and you can accept that and expect it, and move on. Or, don’t grow those varieties at all. I like to grow several varieties of tomatoes every year, which also helps makes BER less devastating.
  4. Add more calcium to your soil. It can’t hurt, but because sources of calcium need to break down to become water soluble and available for plants, expect this to take months. You have many options for adding calcium, including crushing eggshells yourself, or purchasing fertilizers.
  5. Eat what’s left. Cut off the bottom and enjoy anyway. I’ve never noticed a taste difference in the healthy part of affected fruit, and it is not harmful to ingest.
Blossom End Rot is not as devastating as it may appear, just a real annoyance. Do what you can, and hope it doesn’t last.
Side-by-side comparison of the effects of Blossom End Rot on San Marzano tomatoes
Another view of the effects of Blossom End Rot on a San Marzano tomato.


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