Blossom-End Rot

How to Identify and Prevent Blossom-End Rot

Chris Burnett

Here are tips on how to identify, control, and prevent blossom-end rot on your tomatoes and other garden plants.

What Is Blossom-End Rot?

Are your tomatoes rotting on the bottom? Unfortunately, they likely have blossom-end rot. It’s a common problem on tomatoes, peppers, eggplants, and squash. Blossom-end rot is a disorder in which the tissue of the blossom end (the “bottom”) of the fruit breaks down and rots, thus reducing quality of the fruit and the overall yield from the plant.

What Causes Blossom-End Rot?

Blossom-end rot is caused by a lack of calcium in the plant. This lack of calcium may be due to low calcium levels in the soil or—more typically—soil that is over- or underwatered. When there are wide fluctuations in soil moisture, this reduces the plant’s 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’ roots

Be aware of these causes when caring for tomatoes and other garden plants in order 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.

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

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

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 appears as brown, sunken spots on the bottom of the fruit. Photo Credit: North Carolina State University.

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 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 they’re still young and more adaptable is also a good idea. See our video on properly staking tomatoes.

Plants Affected

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Reader Comments

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Blossom End Rot

I grind egg shells in my coffee grinder and spread them in the dirt and around the base of the tomato plants. In the dirt provides the need calcium; around the base is a deterrent to any bugs. I also give all my vegetables a good dose of used coffee grounds.

Blossom End Rot

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

blossom end rot.

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

Egg Shells and Calcium

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!

I use milk

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

I put a handful of Crushed

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.

Tomato - blossom end rot

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

Blossom "End-Rot"

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.

I use eggshells

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.

Egg Shells

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.

Tums for tomatoes

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..

tums for tomatoes

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!

end rot tomatoes and other vegetables

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

Blossom end rot

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

Blossom Rot / Calcium

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.

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!

using powdered milk as calcium source for tomatos

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

hi... new to gardening this

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 :)

Hi Kriss, Late blight is very

Hi Kriss,
Late blight is very hard to get rid of. Please read our blog about late blight at
www.almanac.com/blog/gardening...

I have been told that crushed

I have been told that crushed tums is a good source of calcium for the garden. I have not tried it yet but plan to next year.

Crushed Tums

Did the crushed Tums resolve the calcium issue?

I keep on hearing about

I keep on hearing about blossom end rot over the years and usually end up with some of my plants. I keep getting told to increase the calcium level for the plants, but I can never find out where to get the calcium from. I have been told to mix crushed eggshells, but I live on my own, so consequently don't get many. I've asked friends, but they are all in the same situation.

If you have a calcium

If you have a calcium deficiency in your soil, it all starts with soil preparation next year. Start out by adding lime into the to 12 inches of the soil.
To know how much lime to add, it would be best if you knew your soil pH. You want a pH of 6.5 to 6.8 to free up calcium. If you do a soil test, the results will tell you the amount of lime to add. Usually, your county cooperative extension will give you a free soil test.
Adding crumbled egg shells to your compost or burying them in the garden is also a good idea over time.
Also, avoid over-fertilizing, especially with nitrogen which ties up the calcium in the soil.
It also helps to use mulch to keep the soil moisture even.
Keep the soil moist and water evenly. Using a soaker hose at the plant's base is best.
Some readers use calcium sprays as a short-term fix. You'll want to ask your garden center about a spray.