Blossom End Rot ~ Identification, Control, and Prevention


Blossom end rot is a common garden problem, but thankfully we know what causes it. While blossom end rot (BER) most commonly occurs in tomatoes, BER can also happen with cucumbers, melons, eggplants, peppers, and squash.

Blossom end rot (BER) is not a disease. It is a physiological response to a deficiency in calcium, but the solution is not as simple as just adding calcium. BER is often more due to a problem with the transportation of calcium throughout the plant.

What does blossom end rot look like?

BER looks like a brown, irregular spot at the bottom end of the tomato—the part where the blossom forms and falls off. It makes it appear as if your tomato is rotting from the bottom end. See the pictures above and below to get help identifying if your tomatoes have blossom end rot.↓

I can usually spot the formation of BER when the fruits are about 1/3-1/2 their mature size. When your tomatoes are lacking the calcium they need, the tissue starts to break down resulting in the rotted appearance.

Since BER is not a disease, fungus, or infection it cannot be treated with anything like neem oil, fungicides, or insecticides.

Conditions that can cause BER

Before we talk about the things you can do to prevent and control blossom end rot, I’d like to discuss what conditions in your garden might have caused the problem. Remember how I said that the solution is not as simple as adding calcium? That’s because the majority of BER is a result of something preventing your plants from absorbing and uptaking calcium from the soil—not an actual lack of calcium in the soil. Some of these causes are out of your control, so don’t feel bed if you start to see BER in your garden.

Weather. Basically, any extremes in temperature can negatively affect your plant’s ability to pull nutrients from the soil.

Inconsistent watering. For similar reasons listed above, not applying the correct amount of water can cause problems for your tomatoes as they struggle to uptake calcium from the surrounding soil.

Too much nitrogen. More fertilizer is not always better. While nitrogen is great for green, leafy growth, too much nitrogen can prevent plants from being able to uptake calcium! Read How to Amend Your Beds Organically for my tips for prepping a raised bed.

Wrong pH. In most cases, the ideal soil pH is 6.5. When soil pH is too acidic or too basic, this prevents plants from functioning properly. Think of it like an ecosystem—everything functions well when in balance but can be thrown off completely when something is off.

Low levels of calcium in the soil. I wouldn’t jump to this conclusion immediately, but it is possible your soil needs a boost of calcium.

Ways to Prevent BER

1) Prepping your soil properly is the best way to ensure your soil has all the nutrients and macronutrients it needs. If you read up on How I Amend My Garden Organically you’ll find that I top all of my beds with compost. Our homemade compost always has decomposed eggshells, which are a great source of calcium. Friendly reminder: you can’t just add eggshells to your garden and expect the calcium to be available to your plants. It takes a lot of time for eggshells to breakdown and actually become useable calcium.

2) An optional step to preparing your soil is to add some bone meal. I typically do this for my flowering bulbs, tomatoes, and peppers because they do like that extra boost of calcium and phosphorus. *watch your pets when using bone meal and keep them away. I mix it in thoroughly because they can smell it!

3) Select tomato varieties less susceptible to blossom end rot. For example, the tomatoes pictured are ‘san marzano’ tomatoes which are notorious for getting blossom end rot—but delicious for tomato sauce! This year I only had one bunch develop BER, but I suspect it had to do with a water and temperature problem at the time because the rest of the fruit is fine.

4) Know your pH. Ideal vegetable growing pH is about 6.5. If your pH is not correct, this could easily prevent your plants from absorbing the proper nutrients it needs. While I think every garden should have an official laboratory soil test every few years (and in the beginning!), you can use a simple home test for pH like this one, or a more comprehensive home soil test like this one for maintenance purposes.

5) Irrigate consistently and accurately. I know watering is a very confusing topic because no one can really tell you the “perfect” way to water. You never want your soil to be too wet, but you also don’t want it to be bone dry. A good ole trick is to stick your finger down into the soil and see if there is moisture about 1 inch below the surface. If so, don’t water. Eventually you’ll start to get a feel for how much water your garden needs.

6) Mulching will help you maintain more consistent water levels. In fact, I recommend mulch all year round, but especially for protecting your garden from heat. You can learn more about mulch here: How to Protect Your Garden During a Heatwave.

7) Try a specialized, organic fertilizer. If you have had issues with your tomatoes year after year, maybe try an organic fertilizer, like Espoma Tomato Tone, which is specially formulated and has added calcium to fight BER. Remember, do not over-fertilize as this can also lead to problems in the garden.

How to Control BER

Okay, you’ve got blossom end rot, now what do you do? First, I like to remove the damaged fruit. At this point, I don’t want my plant to waste anymore energy on growing fruit that is damaged. I also want to give it the most strength to recover and try to correct the imbalance.

Check your watering and assess the points listed above.

Just because some fruit developed BER does not mean all future fruit will have this problem.

Some sources might jump to adding a source of calcium immediately, but this won’t be helpful if your pH is incorrect and a lot of calcium sources can actually change your pH, making the problem worse. A soil test is a great place to start. Once you determine your pH, you can research what type of soil amendment you can add.

You can try a product like Espoma’s Tomato Tone. If you suspect over-fertilizing is your problem, do NOT add this product. For over-fertilizing, give your plants a good, deep watering once. Nitrogen can be flushed out over time with watering.

Last but not least, try to correct the issues discussed here and then just observe and give it time. Like I said, BER can be a result of weather or moisture fluctuations so the problem could resolve itself!

For more tomato growing information, check out:

Tomato Growing FAQs

⇓ I’d love to hear how your tomatoes are doing! Leave your comments below!⇓

PS: Tag me in your garden photos with #FreckledCA on Instagram!

Meet Randi

Urban gardening is my jam. I’m Randi, California girl who obsessively gardens to grow food and flowers around my urban home. Seasonal, simple living is what inspires me~ I hope it will inspire you too. Join me in crafting a life and home connected to the garden Read More>>>>

For Growers & Gardeners from High Mowing Organic Seeds