蜜桃恋人

How to Identify and Prevent Blossom-End Rot

Photo Credit
Chris Burnett
No content available.

What To Do When You See Blossom-End Rot

Catherine Boeckmann
Pest Type
Plant Diseases
Plants Affected
How to Grow Eggplant: The Complete Guide to Aubergines
How to Grow Bell Peppers: The Complete Guide
How to Grow Tomato Plants: The Complete Guide
How to Grow Zucchini & Summer Squash Plants: The Complete Guide

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
Read Next
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
 

More Like This

Comments

Tomsgrams (not verified)

7 months ago

I do the same do you know how much you use per plants.

Marty S. (not verified)

2 years 6 months ago

Coffee grounds contain nitrogen. Also cold black diluted coffee is good to use. I grow tropical Fiddle Leaf Fig plants and use diluted coffee on them.

Julie Steele (not verified)

4 years 5 months ago

I buy cheap calcium tablets from the dollar store and dissolve them in warm water to treat my tomatoes. No blossom end rot.

Lynn E LeDuc (not verified)

4 years 5 months ago

I put all my egg shells in the dirt. The calcium is good for them.

Egg shells are a great source of calcium, though they are better off being crushed and thrown in the compost pile, as they’ll break down a lot more easily there! 

Ralf Nadir (not verified)

4 years 5 months ago

Just pour milk on ground, have never had this problem.

Michelle Hebbard (not verified)

6 years 3 months ago

I put a handful of Crushed Oyster Shells and a handful of Epsom Salt right in the hole with the plant. Works and it's cheap. Calcium and Magnesium.

Gary Onuschak (not verified)

6 years 3 months ago

This can also be caused by extreme hot weather...

Bill in Idaho (not verified)

6 years 4 months ago

There is One Cure/ Solution for Blossom "End-Rot". Since it is the Result of Calcium (Ca) and Phosphorous (P) Deficiency - Simply Add a Small Amount of Organic Bone Meal to the Top of the soil before watering - Weekly.

Mary (not verified)

6 years 4 months ago

I use eggshells and since I eat them almost daily, it isn't hard to build up a supply. I do rinse them out and pull out the inner lining (admittedly, it's sometime easier said than done). I find they grind up (I use a mortar and pestle) much easier that way. I keep the ground egg shells in a small bucket and in the fall I mix a few handfuls into the smartpots and each section of the square-foot style raised beds. I think it helps if the calcium has some time to leech into the soil before you plant in the spring. Been doing it for the last few years and I've had better luck with avoiding the bloom rot in my peppers.