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  • Writer's pictureKassi Kuppinger

Protect Your Tomatoes from Blossom End Rot

Are your tomatoes suffering from a strange phenomenon where the bottom of the fruit turns an unappetizing opaque color, just to then shrivel up and turn a nasty brown or black color? If so, you are definitely not the only tomato grower experiencing this issue, known as blossom end rot. As the name suggests, this occurs when the blossom end of your tomato begins to decay. This doesn’t mean the whole tomato is rotten, and it can be salvaged by simply cutting the affected area off the fruit. However, this condition is definitely not ideal and does lead to much of your sweet, home-grown tomatoes being wasted.

So, let's get down to the real reason why all of you have been searching the internet, and answer two questions:

What is the cause, and how is it stopped?


Blossom-end rot, though there are several potential causes, is most commonly a result of calcium deficiencies and irregularities. Tomatoes need calcium to be able to grow and develop their lush, ripe fruit, so a lack of calcium will easily cause your tomatoes to rot from the blossom end. Early in the growing season is generally when it is most common to see blossom end rot affecting your tomatoes. This is due to the plants growing rapidly early in the season, channeling most of the available calcium into developing the plant and its foliage. In this case, once the fruit begins to grow, there is not enough calcium left to support healthy development.

This issue in fruit development can also be caused by there simply not being a healthy flow of calcium through the plant. Your tomato plants could have the perfect amount of calcium to fortify the fruit, and still experience rot due to stress factors such as receiving too much or too little water. Insufficient water will result in calcium not making it to every part of the plant, and excessive water will result in the calcium becoming watered down and flushed out of the plant, depriving it of the sustenance it needs. Factors such as root damage or excessive levels of nitrogen in the soil can also have an affect on how the plant absorbs calcium.

Watering and Consistent Moisture

This will serve as a huge help when attempting to prevent blossom end rot, or even when trying to get it under control once it has already begun to affect your plants. Maintaining a consistent level of moisture throughout your plant's growing season will help regulate the amount of calcium it absorbs. When it is particularly dry out, make sure the moisture levels of the soil around your tomato plants reaches at least 6 inches. Tomato plants need at least 1 1/2 inches of water per week if they are going to avoid decay.

Another easy way to help maintain consistent moisture around your tomatoes is to spread some mulch at the base of each plant. This will lock in much of the moisture that escapes when the sun comes out. Minimizing evaporation in this way will go a long way in helping you make sure your tomato plant is getting just the right amount of water. If you don’t have mulch handy, this can also be accomplished with straw or grass clippings, sheets of plastic, or newspapers.

Root Damage

If this is the factor that is causing issues with your tomato plants, there really is not much you can do. Try to leave the plant alone. Be very careful not to agitate its roots, as this is likely what caused the root damage in the first place. Simply water your tomato plant and give it all the love you would normally, and hopefully, its roots will heal and grow, reaching a state where they will be able to absorb the appropriate amount of water once more.

Nitrogen Toxicity

Even though plants do need a lot of nitrogen for normal, healthy growth, too much can also do a lot of damage to your tomatoes. Most often, nitrogen toxicity in tomato plants can be identified by “burned” leaves, where the tips turn brown and crunchy. Depending on the kind of plant, nitrogen toxicity can also be identified by extremely dark green leaves, or by the leaves turning a very pale yellow color. If you believe this to be the issue at hand, simply soak the dirt around your plant. You likely have soil with a higher concentration of nitrogen than normal, so watering around your plant will help flush some of this excess nitrogen out of the ground. If you have been using a fertilizer, the nitrogen toxicity could be from you over-feeding your plants. Do not apply any more nitrogen-rich fertilizer, and water thoroughly to help flush out the excess.  


Now I know I just said to stop fertilizing, but your plants do still need some help! We know to stay away from fertilizers high in nitrogen since this could be contributing to the issue. However, using a calcium-rich fertilizer might be just what you need. One of our favorite products is Age Old Calcium. This formula is made specifically for correcting calcium deficiencies and helping to strengthen the cell walls of your tomatoes, yielding plump and firm results. With calcium playing such a large role in the development of strong and fortified cell walls, this fertilizer is also helpful in preventing other attacks from pests and disease. The application of this product will vary depending on the type of plant and its maturity, so stop into the store or give us a call, and we can help determine the best application for your plants!  

Free help! All you have to do is ask.

These products are all available at our garden center as well as in our online store, along with other products suited to help your garden grow to its full potential. So come pay us a visit! We would love to be able to help with any of your questions or concerns.   


Espiritu, Kevin. “Nitrogen Toxicity: Understanding and Preventing It In Your Garden.” 11 January 2019. Web. Date accessed 14 July 2020. Retrieved from

Gardener’s Supply Company. “How to Control Blossom-End Rot on Tomatoes.” 14 March 2019. Web. Date accessed 14 July 2020. Retrieved from

George. “Calcium (CA): Essential For Plant Growth and Development.” Age Old Organics. 2 June 2015. Web. Date accessed 14 July 2020. Retrieved from

Stallsmith, Audrey. “WHat is the Amount of Calcium to Add to Tomato Plants?” 28 November 2018. Date accessed 14 July 2020. Retrieved from


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