蜜桃恋人

How to Identify and Prevent Blossom-End Rot

Photo Credit
Chris Burnett
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What To Do When You See Blossom-End Rot

Catherine Boeckmann
Pest Type
Plant Diseases
Plants Affected
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Do your tomatoes look as if they are rotting? The culprit is probably blossom-end rot! This frustrating problem can appear to come out of nowhere. Here are top tips for preventing blossom-end rot on your tomatoes and other garden plants.

What Is Blossom-End Rot?

Are your tomatoes developing a dark, sunken spot on their bottoms? Unfortunately, they likely have blossom-end rot. It鈥檚 a common problem for fruiting garden plants such as tomatoes, peppers, eggplants, and squash. Blossom-end rot is a disorder in which the tissue of the blossom end (the 鈥渂ottom鈥) of the fruit breaks down and rots, thus reducing the quality of the fruit and the overall yield from the plant.

What Causes Blossom-End Rot?

Thankfully, blossom-end rot isn鈥檛 caused by a disease or pest. Instead, it is the result of a lack of calcium in the plant. This lack of calcium may be due to low calcium levels in the soil or鈥攎ore often鈥攕oil that is over- or underwatered. Wide fluctuations in soil moisture reduce the plant鈥檚 ability to take up calcium from the soil. When the demand for calcium exceeds the supply, the tissues in the fruit break down, and blossom-end rot occurs.

In addition to watering issues, calcium deficiency during fruit formation may also be caused by:

  • Too much nitrogen-heavy fertilizer
  • Improper soil pH
  • High salt levels in the soil
  • Damage to plants鈥 roots

Awareness of these causes when caring for tomatoes and other garden plants is the best way to prevent blossom-end rot.

Some blossom-end rot is more or less normal in the first tomatoes of the season since the plants are usually under stress during the initial fruit set. It also tends to happen more often in plants grown in containers, as the soil is more susceptible to fluctuations in moisture. In other words, the plants dry out too much, and their fruit is affected. 

If the damaged portion of the fruit is small, you can trim it off and enjoy the rest of the fruit. Hopefully, the problem will fade with the prevention tips below!

Blossom-end rot on tomatoes. Photo by Chris Burnett
Blossom-end rot starts out as a small, bruised area near the bottom of the fruit. Photo credit: Chris Burnett
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Identification

Signs of Blossom-End Rot

Usually, blossom-end rot appears while the fruit is still green or ripening, so it often affects the first fruits formed on the plants.   

Blossom-end rot starts with a small, depressed, water-soaked area on the blossom end of the fruit (the bottom, opposite the stem). The spot starts off looking like a dark bruise. As the spot enlarges, it becomes sunken and turns black or dark leathery brown in color. Half the fruit may eventually be affected.

blossom end rot on tomatoes
Blossom-end rot appears as brown, sunken spots on the bottom of the fruit. Photo Credit: North Carolina State University.
Gardening Products
Control and Prevention

How to Prevent Blossom-End Rot

As mentioned above, blossom-end rot is a condition caused by a lack of calcium. Unfortunately, the rot will not go away once a fruit is already affected, but following the advice below can stop the rot from progressing further and from affecting other developing fruit.

  • First, choose vegetable cultivars that are tolerant of calcium deficiencies and less likely to show blossom-end rot symptoms.
  • Inconsistent watering is the main cause of calcium deficiency. Avoid watering your plants too much or too little. Instead, water consistently and evenly. If you forget to water, do not overwater. If it’s rainy, ensure plants have good drainage and the soil dries out (but do not cease to water completely). Overall, plants need about 1 inch of water (about 0.6 gallons) per square foot per week.
  • Use mulches to retain soil moisture during dry periods.  
  • Have your soil tested periodically to determine if there is sufficient calcium in the soil. If you’re using new, store-bought soil, it will likely have more than enough calcium in it already. However, if you’re growing in older soil, calcium levels may be depleted. If your soil test confirms this, add an organic source of calcium such as lime, bonemeal, or finely crushed eggshells. 
  • Check the soil pH on a regular basis, particularly if you use lime as a calcium source. A pH of about 6.5 (slightly acidic) is ideal for growing most vegetables, as it allows for the best nutrient uptake.  
  • Because blossom-end rot is caused by a calcium deficiency, you might be tempted to just fertilize your plants more. However, in most cases, there is already sufficient calcium in the soil; the plants just cannot absorb enough of it. Overfertilization is also harmful, and having too much nitrogen, magnesium, and potassium in the soil can actually make blossom-end rot worse. If you are going to fertilize, follow this advice:
    • Consider using a fertilizer that is formulated to contain more calcium.
    • Use a product that contains nitrate nitrogen instead of ammonium nitrogen (as the latter may contribute to more blossom-end rot).
    • Avoid over-fertilizing during early fruiting, when blossom-end rot is more likely to occur.
  • Avoid cultivating or digging near the roots of plants, as root damage can affect their ability to absorb water and nutrients.
    • Staking plants like tomatoes while still young and more adaptable is also a good idea. See our video on properly staking tomatoes.
Plant Disease
About The Author

Catherine Boeckmann

Catherine Boeckmann loves nature, stargazing, and gardening so it鈥檚 not surprising that she and The Old Farmer鈥檚 蜜桃恋人 found each other. She leads digital content for the 蜜桃恋人 website, and is also a certified master gardener in the state of Indiana. Read More from Catherine Boeckmann
 

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Comments

Tomsgrams (not verified)

7 months ago

Thank you, I have all the egg shells ground up and will add each to the plant as I plant them. Then this fall I will spread the rest to each box.

Terry (not verified)

6 years 4 months ago

I keep a ziploc bag in the freezer and put the egg shells in there. When I'm ready to use them, I put the shells in the blender with some water and make a slurry.

Ken (not verified)

6 years 5 months ago

A lady at the Framer's Market told us her trick.. She puts a couple of Tums in when she plants her tomatoes. She buys a big bottle of Tums which is inexpensive and easy.. As we live in the mountains; a lot of other remedies would attract the br'er raccoon family..

As it was too late for us; we had to buy calcium spray..

Joy Lewis (not verified)

6 years 4 months ago

that is exactly what i did last year and had huge roma tomatoes with no end rot at all. Hoping for same success this year!

jean (not verified)

6 years 3 months ago

Well, tums and other calcium items did not help. I will start over again in another spot in my garden. the tomato plants, squashes and green peppers started out nicely, but as time went on, they got the end blossom rot. I will start over again with crushed up egg shells. jean

jacques (not verified)

6 years 6 months ago

to prevent blossom end rot, what I do is When the plants start to bloom, I mix 1 par of non-fat milk with 4 parts of water and I use 1 cup of this mixture to water each tomato plant after watering the soil well, because of the calcium in the milk this prevents blossom end rot..it works for me

Lynn (not verified)

8 years 3 months ago

When planting my tomatoes, I always throw a handful of crushed oyster shells in the ground with a light dirt covering and then spread them out around the stem to stop any slugs from stopping by. The calcium helps the plants and the slugs won't crawl across the sharp bits of shell.

Bonnie Thielke (not verified)

10 years 1 month ago

Add powdered milk

I am fairly new to gardening, only 3 years of ground gardening and 1 year of straw bale gardening. In the book I read about straw bale gardening, "Straw Bale Gardens" by Joel Karsten, Mr. Karsten mentioned adding powdered milk (high in calcium) to the hole before planting the tomato plant. I did this and did not have any issue with bottom rot. I had a wonderful harvest of healthy tomatoes, except when the slugs starting coming. I took care of the slugs with Mr. Karsten's suggestion of putting a shallow container with some beer in it and sinking it in to the bale a little so it is easy for the slugs to crawl in but not crawl out. The slugs preferred the beer over my tomatoes, which made happy. I will definitely be planting in straw bales again next year!

lynn williams (not verified)

7 years 5 months ago

I am wondering if you had any success using the powdered milk.

kriss (not verified)

10 years 1 month ago

hi... new to gardening this past year. we did pretty good until what people are calling 'late blight'. i was told once you have 'it', it stays in the soil. ???sounds like from reading this i can ammend the soil next year and will be fine??
please advise... and thank you :)