How to Treat Blossom End Rot (It's Not Just a Calcium Deficiency!)

How to Treat Blossom End Rot: It's Not Just a Calcium Deficiency!
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Lately, I've been seeing a lot of questions about a common problem people have when growing tomatoes, summer squashes, eggplant, peppers, and melons. It's called blossom end rot and gardeners know their plants have it when the bottom side (the blossom end) of the fruit looks like it's rotted. The good news is this: Blossom end rot has an easy, quick, organic fix. Or actually, fixes. That's because there is more than one thing that can cause blossom end rot. Here's how to manage it.

Cause #1: Lack of Calcium

Unless you live in an area where the soil is naturally rich in calcium, or you've tested your soil very recently and know its calcium levels are good, lack of adequate calcium is the most likely culprit for blossom end rot. My recommendation is to first give your plants a quick dose of calcium using something you probably already have in your house: TUMS, or any brand of chew-able antacid (but not the gel of gummy type). Simply bury the tablets around the plant in question and water in well. This will get your plants out of immediate trouble...but won't have lasting effects, so you'll need to further supplement calcium in the soil, using one of the following:

* Bone meal. This is my #1 preferred choice. It releases into the soil a bit more slowly than the items mentioned below, but in my experience it is the easiest to find in local stores.

*  Dolmite lime (Calcium carbonate). This will also raise magnesium levels in the soil, which is not a good thing if your magnesium levels are already on the high side. It will also raise the pH of your soil, making it less acidic.

* Hardwood ashes. Do not uses ashes from soft woods, since they are much lower in calcium. Ashes work well if your soil pH is below 6.5. (If the pH is above 6.5, hardwood ashes can interfere with plant growth.) It's also important to know that wood ash raises soil pH, phosphorus, and magnesium.

* Gypsum (Calcium sulfate). Make sure it is marked organic.

All these products will add calcium to the soil relatively quickly.

In the future, when you plant crops that are more likely to develop blossom end rot, you may wish to add amendments to the soil as you plant. In addition, consider adding amendments that take longer to break down at the end of the growing season, so the soil is ready to go in spring. Calcium amendments that break down slowly include:

* Ground up egg shells.

* Ground up oyster or clam shells. 


Blossom end rot on summer squash. Courtesy of kirybabe.

Cause #2: Not Enough Water

If you know your soil has plenty of calcium, it's likely you aren't watering often enough. This results in plant that can't access the calcium that's in the soil. Consistent and deep watering will solve that problem.


Cause #3: Too Much Nitrogen

If you think your plant's blossom end rot is caused by excessive use of nitrogen fertilizers, all you can really do is stop fertilizing immediately and learn from your mistakes.


Blossom end rot on tomatoes. Courtesy of
Scot Nelson.

Cause #4: Poor Pollination

If you're absolutely sure lack of calcium, not enough water, or too much nitrogen isn't causing the blossom end rot in your garden, it's possible poor pollination is to blame. Your best bet, then, is to hand pollinate your tomato, pepper, summer squash, melons, and eggplant flowers. This isn't as difficult as it may sound, and The Kitchn offers a great tutorial on how to do it.


  1. Thanks for sharing with us at Farm Fresh Tuesdays Blog Hop! Your post is one of my features at this week's hop. Be sure and stop by to see your feature and say hi!
    Melissa | Little Frugal Homestead