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You are here: Home / Gardening / How to Prevent and Manage Blossom End Rot in Your Garden

August 9, 2024 By Candace Godwin 2 Comments

How to Prevent and Manage Blossom End Rot in Your Garden

Our recent extreme temperatures are causing a lot of stress in the garden, not only for the plants but for gardeners as well! It’s becoming a full-time job keeping the garden watered and protected from the high heat. 

The question always remains – are we watering too little or too much? Unfortunately, both can result in the dreaded condition of blossom end rot.

ripening tomato with blossom end rot
There’s nothing more disheartening than discovering blossom end rot on your ripening tomato.

What is Blossom End Rot?

One of the most misunderstood conditions in our gardens is blossom end rot (BER). It’s a common disorder in tomatoes, however, it also affects peppers, eggplant, squash, and pumpkins.

BER can easily be identified in tomatoes by a water-soaked or dark brown leathery patch on the blossom end of the fruit. Mild cases may be represented as a stippling of spots on the fruit bottom.

blossom end rot on green tomato
The early stages of blossom end rot appear as water-soaked dark spots.
advanced blossom end rot on green tomato
A more advanced case of BER with a dark patch on the side and bottom.
mild case of blossom end rot on ripe tomatoes
These tomatoes exhibit a mild case of blossom end rot. Note the stippling of the skin.

Similar characteristics are also found in eggplant with BER, while peppers exhibit a tan lesion on the bottom or side that resembles sun-scald. If pepper fruits are shaded by leaf cover, yet show sunscald symptoms, it’s most likely BER. 

blossom end rot on a chili pepper
Blossom end rot in peppers looks very similar to sun-scald (sunburn). These peppers have been out of direct sun, so this is BER.

In squash and pumpkins, it can be a bit more difficult to identify correctly, since blossom end rot often resembles incomplete pollination; where budding fruit yellows, withers, and falls from the plant. A squash fruit with BER is usually more developed and will have a dark patch on the end.

incomplete pollination in squash
Given the size of this fruit, this appears to be incomplete pollination and not blossom end rot.
Again, this looks more like incomplete pollination, but it may be BER.
This winter squash appears to have blossom end rot. Often the blossom will remain attached.
Photo: Alyssa McMillen
blossom end rot on yellow squash
There is no question with this yellow squash – it’s blossom end rot. Photo: Merry Ruth Dingman.

It’s quite shocking the first time you encounter it – what in the world is this awful-looking rotting patch on my lovely tomato (zucchini or pepper)? If there’s any good news, blossom end rot is a physiological disorder – not a disease; it won’t spread to other plants.

The Calcium Culprit

BER is caused by the plant’s inability to absorb calcium from the soil or move calcium within the plant. The result is a calcium deficiency within the developing fruit that appears as a rotting spot on the fruit.

Blossom end rot is a physiological disorder, not a disease. It’s caused by a calcium deficiency, often due to fluctuations in watering.

Since calcium isn’t very mobile within the plant, anytime the absorption or movement of calcium into the plant is slowed, blossom end rot will likely occur. Sometimes BER only affects one fruit in a cluster, or just a few fruits on one side of the plant. Again, it relates to how calcium moves within the plant to the developing fruits. 

Plum and pear-shaped paste or Roma-type tomatoes are more susceptible than other tomatoes. Sometimes only one or two fruits on the plant are affected.

It is important to understand that BER is not caused by a lack of calcium in the soil. While plants absorb calcium from the soil, low soil calcium levels are rarely the cause. Most soils in our region have sufficient calcium.

Blossom End Rot Triggers

Blossom end rot can be a sporadic or persistent problem, depending on what’s preventing calcium from reaching the developing fruits.

Various stressors can affect how calcium moves in the plant; plant stress related to unusually cool or hot weather (North Idaho springs and summers!), drought, or wet soil conditions can trigger BER.

In our region, blossom end rot typically occurs when plants with rapidly developing fruits are exposed to drought or excessive water (over-watering or rain). It’s also fairly common on susceptible plants grown in containers due to sporadic watering and over-fertilizing.

BER can also be caused by root damage from cultivation, over-fertilizing with nitrogen, high salinity in the soil, or acidic soil (pH below 5.5); however, the most common culprit is fluctuations in watering.

Steps to Reduce BER

Social media is full of solutions for curing or preventing blossom end rot. Unfortunately, there is no “cure” for the condition. Likewise, crushing eggshells or adding powdered milk, or worse yet, adding TUMS antacid tablets to the soil won’t prevent blossom end rot. Commercially sold calcium sprays won’t cure the problem either. Don’t waste your time or money with these “remedies.”      

However, there are several things you can do to reduce the occurrence of blossom end rot in the garden.

Watering: First and foremost, be mindful of how you water your plants. Focus on water management to minimize drought stress or waterlogging plants. Water regularly and deeply throughout the growing season. Use a water meter to gauge moisture in container-grown plants.

Mulching: Apply a layer of mulch around the base of plants to conserve moisture. Straw, dried leaves, and herbicide-free grass clippings are good options.

Plant Resistant Varieties: Plum and pear-shaped tomato varieties tend to be more susceptible to BER than round tomatoes; it rarely (if ever) occurs in cherry types. Due to the number of factors that trigger the disorder, a definitive list of resistant and susceptible plant varieties isn’t available.

Test the Soil: Blossom end rot typically occurs in the first fruits on the plant and then diminishes. If the condition persists throughout the season on susceptible plants, it’s time for a soil test. Low pH, excessive nitrogen, or salts in the soil can all cause a reduction in calcium absorption. The only way to determine this is by a soil test. UI Extension Kootenai County Master Gardeners can provide information on soil testing.

Cultivate with Care: Damage to plant roots from cultivation can trigger BER. Take care when digging around the base of plants.    

Keep It or Toss It?

While the condition is unsightly, a ripe tomato affected with BER can be salvaged; just cut the leathery end off. The remaining fruit is edible – yes, it really is.

Of these ‘Cream Sausage’ Roma-type tomatoes, only one on the plant exhibited blossom end rot. The brown patch can be cut off and the remaining fruit is completely edible.

However, when I discover BER on green tomatoes, I’ll remove them from the plant to allow the energy to go to healthier fruit. I do the same with affected ripe and developing peppers and eggplant. In most cases squash won’t recover from BER, affected fruit should be removed from the plant. Trust me, more squash will come!

While discovering blossom end rot can be disheartening, it’s important to remember that it’s not a disease and doesn’t spell doom for your garden. Although you might need TUMS when encountering blossom end rot, your plants do not (or any other internet remedies). Keep your watering routine steady and look forward to an abundant harvest ahead.

Filed Under: Gardening, Growing Tomatoes Series Tagged With: BER, blossom end rot, calcium, calcium deficiency, end rot in peppers, end rot in squash, end rot in tomatoes, garden watering, hot weather watering, incomplete pollination, managing blossom end rot, mulching, overwatering, preventing blossom end rot, soil testing, sun scald

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Comments

  1. Sheila Anderson says

    August 10, 2024 at 7:01 am

    Candace, really appreciated this article on BER and remedies. I always thought it was due to overwatering and lack of calcium so your insight has been noted. Especially liked the last paragraph about ME needing the Tums after encountering BER on my zucchini. Thanks

    Reply
    • Candace Godwin says

      August 10, 2024 at 7:23 am

      Sheila, thank you for your comments! BER is always tough to deal with. I’ve had more this year on my container-grown plants than I’ve ever had, thanks to the hot weather and me keeping things a bit too watered. It happens!

      Reply

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