Blossom End Rot, the “Un-Disease”

blossom end rot, tomato problem, rotting tomato

Blossom end rot is one of the more common tomato “diseases.” I put that in quotes because technically, there is no pathogen at play with this condition. Praise God it’s not contagious! Most experienced home tomato growers hardly think about blossom end rot (a.k.a. “BER”). Of course, no one is happy to have it crop up in the garden, but experienced gardeners know what to do about it and are not particularly concerned when we see it.

What is Blossom End Rot?

BER is a condition which causes a tomato, pepper or other kind of fruit (I’ve seen it in eggplant) to get a rotten spot on the end, usually about where the flower was attached. It starts out as a moist dark spot, which rapidly rots. A lot of times the rotten area will dry and kind of mummify, leaving a sunken black spot. The appearance of blossom end rot might make a person wonder if leprosy can infect the vegetable world.

Cornell University Extension on Blossom End Rot

What causes Blossom End Rot in Tomatoes?

Technically it occurs because of a calcium deficiency. Beware, though! The deficiency usually isn’t because the soil is deficient in calcium. Usually it’s because conditions cause the plant to have difficulty obtaining the calcium. The conditions that do this are:

  • Unusually dry
  • Unusually wet or, more often…
  • Fluctuating wet and dry soil conditions

BER becomes even more of a problem if the plants were transplanted into the garden while extra tender or are practically stunted from being in their pots/trays too long. In a nutshell blossom end rot is caused by stress to the plant.

When does Blossom End Rot Appear?

Most often BER shows up early in the season. In my experience the vast majority of cases are found in the very first fruit set after the plant has been transplanted into the garden. Often, the plant is set into the garden right when conditions go from cool and damp to hot and dry. But blossom end rot in tomatoes can be provoked by either overly moist or overly dry conditions. Thankfully, except in the absolute most extreme circumstances, blossom end rot normally clears up on its own.

blossom end rot, rotten tomatoes
“Blossom-end rot” by Mizzou CAFNR is licensed under CC BY-NC 2.0

What Should I do about Blossom End Rot?

If possible correct the moisture issue.

If you need to water, water correctly. Daily, superficial watering is more likely to cause problems than to solve them. See Six Principles for How to Water A Garden.

Mulch, mulch mulch!

“Mulch” is almost anything used to cover the soil. This conserves moisture and keeps soil temperature more steady. These things are a major help in preventing or correcting blossom end rot. Additionally, mulching reduces weeds and enriches the soil. What’s not to love about mulch!?

What about applying fertilizers, Epsom salts, egg shells or antacid tablets to the soil?

Some of these things may work, but there is one hitch: you need to know exactly what your soil is lacking before applying such things. That means you need to get a soil test. North Carolina State University’s Extension Dept. has a good guide to why get a soil test and what’s involved in doing it. I like how they start their article: “Fertilizing plants without knowing the soil pH and fertility is like planning a trip without knowing the starting point.” Click here to read the entire article. I’m not against adding coffee grounds or things like or egg shells to the garden, but I would be wary about other additives, especially fertilizers or salts of any kind. You have to KNOW what you have before doing anything that drastic. Otherwise, just use compost and mulch. Your garden will most likely do alright.

One last suggestion about BER: Don’t sweat it.

Most of the time it will clear up on its own. For your part, just try to maintain soil moisture at a steady level and the plants will sort things out on their own.

Do you have a question about a garden problem? Use the comments area below and ask! We can always use new ideas about what to write.



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