Conquer Blossom End Rot

Dark spots on the bottom of tomatoes are caused by blossom-end rot.

If you see a dark, rotting spot on the bottom of your tomatoes, it’s blossom-end rot. This problem, caused by a calcium deficiency, can be solved a few ways.

When tomatoes, peppers, melons, and eggplant develop a sunken, rotten spot on the end of the fruit, the cause came long before you found the problem. It’s called blossom end rot, and here is why it happens.

Vegetables need calcium for healthy development. When tomatoes, peppers, melons, and eggplant can’t get enough from the soil, the tissues on the blossom end of the fruit break down. The calcium shortage may be because the soil lacks calcium, or calcium is present but is tied up in the soil chemistry because the pH is too low. Also, drought stress or moisture fluctuations can reduce its uptake into the plant. Another reason is that too much fertilizer causes the plant to grow so fast that the calcium can’t move into the plant quickly enough.

The best way to get around all this:

Green tomatoes also may develop this problem, which is a calcium deficiency.

Unripe tomatoes can develop blossom-end rot, too.

Start now by testing the soil. Although most vegetables do well with a soil pH of 6.2 to 6.8, for those with blossom-end the pH should be 6.5 to 6.8 to free more calcium in the soil chemistry. Test results will indicate the amount of lime to add. Even better, lime also contains calcium. Work the lime into the top 12 inches of soil. Use a lime labeled “fast-acting,” which is better than ground limestone unless you have weeks to wait for the lime to react in the soil. If the pH is already correct, the soil test will recommend a different calcium source, such as gypsum.  Also, add crumbled egg shells to your compost or bury them in your garden over time to help maintain the calcium levels.

Don’t over-fertilize. Too much nitrogen during early fruiting, especially with nitrogen made from ammonia, ties up calcium in the soil chemistry.

Avoid moisture stress. Use mulch to keep the soil evenly moist. Vegetables need about 1 to 1 1/2 inches of water a week while fruiting. The best way to water tomatoes planted in the ground is with a soaker hose. In hot climates it is especially tricky to keep big tomato plants in pots watered well during the summer. Make sure to water them daily or set them up on a drip system with a timer.

As a stop-gap measure, spray tomato plants with a calcium solution made for blossom-end rot. Follow label directions. Apply two to three times a week, beginning when the first blooms appear. This is not a long-term fix, but it may salvage your crop until you can take the steps mentioned above. The spray seems to work better on tomatoes than other vegetables.

29 Comments

Joe D

My grand parents always mixed bone meal in the planting soil before planting tomatoes. I never knew what blossom end rot was until I retired to central Oregon. I’m now close to 80, and I realized I didn’t add bone meal the last year and found out what blossom end rot was!

Martha Mokarry

Blossom end rot suggestion. I follow the planting techniques of my father. I dig a deep hole and add a handful of powdered lime and mix it into the soil. I’ve never had blossom end rot using this method. I also add Epsom salt solution to my pepper plants and they thrive. All my vegetables get planted in huge containers.
As for planting early tomatoes I put a cage over the plant and cover the cage with a dry cleaning bag with holes punched in the sides and top. These bags are thinner plastic than trash bags and clear for sunlight. Clothes pins hold the bags in place. I leave the plastic “hot houses”over the plants until Memorial Day. I have beautiful tomatoes by the end of June or first of July. Tomatoes need night temperatures of 55 degrees F at night to set blooms.
I’ve had great success with all my Bonnie plants.

alexandra

We mistakenly bought the german queen heirloom variety in early May, not knowing that it is not a heat-lover. Yet, we continued to water it in order to keep it alive until the fall, where the weather started cooling down (Nashville, TN). We were thrilled when we saw that a gorgeous, giant tomato began to form. Unfortunately, a week or so into the growing process, we noticed blossom end rot, and our lone tomato looked as though it was rotting from the bottom up, shriveling away almost the entire fruit.
Does this mean the rest of the plant will also produce tomatoes with blossom end rot? Should we get rid of it, or wait to see what happens?

Mary Beth

Alexandra,
So sorry to hear! Your plant will continue to bloom and produce for you until the end of the season in Nashville, so don’t give up hope yet. Blossom end rot occurs when the watering is inconsistent, the plant experiences a dry spell, or over-fertilized. Not to repeat the above article, but if you take action outlined in the steps above, your plant will then be able to access the calcium in the soil and future fruits will be fine. ~Mary Beth, Bonnie Plants

Luis

I have lost 2 heirloom tomato plants due to dark spots on leaves and branches and plant dried out, looks like fungus. I live in Miami, Fl. Can you help? Thank you.

Mary Beth

Hi Luis,
Sorry to hear that. If you would like a true plant diagnosis, it would be easiest to help if you share photos (if you still have the plants). Or, you can describe the symptoms and care in an email. Send to our “Ask An Expert” service, where we connect you with a local Cooperative Extension agent. There are so many tomato virus and fungal options that it will be easiest to ascertain that way. If you have other tomato plants nearby, it’s best to diagnose and properly dispose of affected foliage. ~Mary Beth, Bonnie Plants

Lacy

I have alot of tomatoes on my 5 plants, but nothing is turning red. All the tomatoes are green. I live in Orlando, Florida. Please help!

Kelly Smith Trimble

Hi Lacy,

Sometimes, it can take a while for tomatoes to ripen. How quickly they ripen depends largely on sunlight and temperature. Tomatoes ripen best at temperatures in the 80s. The lower (or higher) the temperature is from the ideal, the longer it will take a tomato to ripen. Avoid excess fertilizer at this time to help with the ripening process. Also make sure they are getting the full 6 to 8 hours of sun the plants need so the fruit will ripen.

If a frost is coming (unlikely in Orlando) or if you just want to enjoy those red tomatoes sooner, you can pick the green tomatoes and ripen them in well-ventilated, open cardboard boxes at room temperature, checking them every few days to eliminate those that may have spoiled. Mature green tomatoes will ripen in 14 days at 70 degrees F and 28 days at 55 degrees F.

I hope this helps, and happy growing!

Kelly, Bonnie Plants

chuck

Tomatoes need darkness to ripen…its not the amount of light. Thats why when you have late green tomatoes that refuse to ripen , you place them in a paper bag on the countertop. darkness and the methane given off by a ripe fruit such as an apple.

Missy

If I see end rot on the bottoms of my baby tomatoes that are still growing should they immediately be discarded or can I rescue them with calcium?

Kelly Smith Trimble

Once the fruit has end rot, it’s best to remove it, or remove and cut off that section of the fruit and salvage the rest. You can start spraying the calcium spray on the plant to help prevent future fruit from going the same way.

Rachel

First time gardener with 4 mini-first time gardeners! My kids and I planted a garden are beginning to see success. We are all so excited and they are actually eating raw vegetables!! They were most excited to see the our watermelons growing. Unfortunately I have learned that they have end rot from reading many posts. Is it too late to add calcium? The plant is quite large and sprawling (think Little Shop of Horror). I read above about lots of tomatos, I’m just wondering if it’s too late for my watermelons.. Thanks for your help!

Kelly Smith Trimble

Hi Rachel,

That is great news about your kids loving to eat raw vegetables! That makes me so happy. I know how they feel about seeing the watermelons grow. One gardeners described them as “adorable” on our site, and they truly are! Except when they get end-rot, that is. My guess is that your plants went through a dry spell and then had an influx of water. Maybe you’re experiencing a drought but then got some rain? When this happens, plants take up water quickly and end-rot occurs. The best defense is to keep your plants consistently well-watered. You can also try adding calcium (no, it’s not too late) but the consistent watering is key, too. I hope this helps you and your little ones grow some watermelons. You can “Like” us on Facebook and share pictures of your family garden…we’d love to see them! Happy growing!

Kelly, Bonnie Plants

Kelly Smith Trimble

Hi Linda,

Yes, you can use egg shells for squash, too. This isn’t a fix-all but it’s worth a try. Happy growing!

Kelly, Bonnie Plants

Jan Williams

I usually have -and/or try to keep outdated eggs (cheap ones from Aldi’s and just put an egg in bottom of hole when planting in addition to adding crushed egg shells to garden/compost all year. Haven’t had much of problem with end-rot. Jan

Kelly Smith

Hi Jan,

Thanks for the tip! Yes, the egg can add calcium to the soil. This method isn’t scientifically proven, but if it works for you, it works! Read my colleague Mary Beth’s blog post “Incredible Eggs in the Garden.” She’s testing the egg method this season, too, and should report back later in the season.

Happy growing!
Kelly, Bonnie Plants

Shannon

I had blossom end rot my first year and then was informed by a seasoned gardener that egg shells mixed in the soil at planting prevents it. I am going into my fourth year of growing and the last two years have been blossom end rot free because of my egg shells! This is even during a very rainy and humid season last year when we had tomato shortages all over OH. Mind kept going strong!

Mary Beth

Hi Shannon,
That is fantastic news! Calcium in any form available for the plant’s intake is a necessity to prevent blossom end rot. They also require consistent watering, which it appears you had in the “very rainy season.” I’m glad to hear from your personal experience it does the trick. In my own garden, I’m trying it this year, too. In fact, I wrote an “egg” themed post at Easter on the very topic! Hoping I have the same successful experience you have. ~Mary Beth @ Bonnie Plants

Bill Perez

I have a raised garden 4×8 with soaker hose,garden mix, mulch etc. Live in southern calif, San Bernardino area.How far should the water be soaking down. now I water every othe day for 10 min. thank you

Rose Pezzato

What is the best insecticide to use for my plants? They are in containers, but something is eating the leaves on my pepper plants.

Brian

When I battled blossom end rot, an elderly gardener pointed out that a simple spray bottle with any kind of milk in it spritzed on the plants’ leaves until soaked would absorb calcium faster than any other method. I’ve done this each time it’s reared up in containers or ground planted tomatoes and it has worked perfectly! Long term, the lime addition is the way to go, but when your tomatoes need rescuing NOW, milk does a veggie good.

Sarah Noyes

What type of milk do you recomend to put in a spray bottle: whole, skim 2% or powdered milk? I have blossom rot on my tomato plants.

Kelly Smith

Hi Sarah,

If you grow tomatoes, you’re bound to run into blossom-end rot at some point. You can read more about and get a better understanding of blossom-end rot in our article “Conquer Blossom-End Rot”. This physiological problem is caused by the plant’s inability to uptake calcium from the soil, due to a variety of potential factors. So to your question about milk… As a home remedy, some gardeners add powdered milk to the soil, which certainly can’t hurt but may not help either (and may cause a stink). Other gardeners spray a milk solution on the plant in an attempt to increase calcium (it doesn’t matter whether whole or skim, just whatever you have around), but it’s not a good idea to wet tomato leaves (which encourages disease) and, again, this may not help either. You can try the milk remedy, but I suggest you read about the solutions we recommend in “Conquer Blossom-End Rot” and try these as well.

Sorry for such a long answer, but blossom-end rot is quite the complicated problem. I hope this helps! If you continue to have problems, use our Ask an Expert service to get additional help.

Happy growing!
Kelly, Bonnie Plants

Shannon

This is good news. While my eggs worked for all my other tomato plants, it does not seem to be working for my roma this year. (First time growing roma tomatoes) I will try this milk method for the immediate calcium. Thanks for posting this!

Suzanne Thornton

First time tomato grower and the plant is growing and has 2 tomatoes. Planted on 1/21/12. The flowers bloom but then dry up but otherwise the plant continues to grow. What to do about the flowers drying up? Thanks. ps – I live in East Central Florida.

Kelly Smith

Hi Suzanne,

Congratulations! I am so jealous of your year-round growing season in Central Florida. Typically, if a tomato plant is not setting fruit, it’s because of hight temperatures. Read our article “Tomato Plants Not Setting Fruit? Here’s Why” to learn more.

Good luck in your first year growing tomatoes! Be sure to consult our How to Grow Tomatoes page if you have questions.

Kelly, Bonnie Plants

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