Blossom End Rot, known as BER, is a disfiguration found in fruiting vegetables, like tomatoes, peppers, watermelons, eggplants, and apples. This problem is usually blamed on a shortage of calcium, but this turns out to be a myth.
Blossom End Rot – What is it?
Blossom End Rot, or BER shows up as a small wet, water-soaked spot at the blossom end of the fruit. Over time, it darkens to a brown or black color and becomes leathery and hard. This is not a disease, as reported by many websites, nor is it the result of insect damage. As the fruit grows, something goes wrong with the normal growth process, and the cells in the fruit start to die. The dead cells turn black and hard. It is a physiological condition due to the plant’s environment.
BER is most common on the first fruits of the season, but it can occur at any time.
The fruit, once affected, will not develop properly, and can be discarded so the plant can focus its energy on newer fruit.
Blossom End Rot – What Causes it?
For years it was claimed that a lack of calcium was causing Blossom End Rot since fruit with BER has low calcium levels.
For some time, scientists thought that the problem is one of moving calcium around inside the plant, not necessarily a shortage. Various ‘transporter’ compounds, such as gibberellins and a recently isolated protein, are responsible for moving calcium to points in the plant where it is needed. Calcium is required for cell growth, and so it is required in fairly large amounts by the developing fruit. When these transporter compounds are not doing their job properly, it results in low levels of calcium at specific points in the plant.
The latest research shows that BER develops in the fruit first and only after it is a problem do calcium levels in the fruit change. What this means is that:
BER causes a calcium deficiency in the fruit – not the other way around.
Once you understand the real problem, it becomes obvious why many of the remedies for BER don’t work.
What Causes Blossom End Rot?
The most common cause is irregular watering, but other environmental factors can also cause BER, including salinity, drought, high light intensity, heat, and ammonia nutrition.
For example, cool temperatures affect the level of gibberellins, which in turn may lead to BER. This may in part explain why BER is more common early in the season when it is cool.
High nitrogen can also cause BER. The high Nitrogen causes excessive leaf growth, which in turn receives most of the water and calcium from the roots, resulting in fruit that has a deficiency of calcium.
How do You Solve Blossom End Rot?
In many cases, the plant seems to grow out of the problem over time. As mentioned above, the first fruit of the season is most likely to have the problem, and after that, fruit grows normally–for no clear reason.
The following are some solutions that have been proposed:
1) Fertilize with calcium. It is possible that the soil is deficient in calcium, and if this is the case, fertilizing with calcium may help eliminate BER. However, most soil has lots of calcium, and if it does have calcium, fertilizing with more will not help the problem. Too much fertilizer may exacerbate the problem by making it harder for the plant to absorb calcium. For example, excess ammonium can make it harder for the plant to absorb calcium.
2) Spray calcium fertilizer on the leaves i.e., foliar feed. Foliar feeding is not a good long-term solution for feeding plants, especially for home gardeners; at best, it is a quick-fix solution. Calcium only moves in the plant via the xylem from the roots, up the plant, and into growing points. Calcium has no ability to flow from the leaves via the phloem to the developing fruit.
An interesting experiment measured the effects of calcium foliar spray on tomato plants and found that it affected both plant growth and reduced BER. It is possible that the increase of calcium in the leaves results in more calcium being directed to the fruit from the roots. This is just one study, but calcium foliar spray may reduce BER.
3) Spray calcium on the fruit. Fruit has a tough waxy outer skin that is not very permeable, and it has no stomata to allow nutrients to enter. It is even less likely to absorb calcium than the leaves. This does not work.
4) Treat the plant with Epsom salts. I don’t know why people keep recommending Epsom salts to solve problems–it’s just silly. Epsom salts are magnesium sulfate–it does not contain calcium! Blossom End Rot has nothing to do with a magnesium shortage.
5) Water more, or less. There is some evidence that water levels in the plant play a role in calcium levels in various parts of the plant, and water levels may have an effect on the transporter compounds. The problem with this advice is that it is difficult to know if you need to increase or decrease water levels. Keep the soil moist and don’t overwater.
6) Grow a different variety of tomato. This can work. Some varieties are more likely to get Blossom End Rot, so growing a different variety could solve the problem for you.
7) Adding bonemeal or lime to the soil. Both these products contain calcium, and if your soil is deficient in calcium, these might help. Keep in mind most soils are not deficient of calcium, so I would not use these products until you have a soil test done.
8) Don’t over-fertilize with nitrogen. This is important and can contribute to BER. Too much nitrogen causes the plant to grow more leaves. As water is drawn towards the leaves, it carries calcium with it, which may in turn reduce the amount of calcium going to the fruit. Over-fertilization also increases the amount of salts around the roots, which makes it harder for the plant to absorb calcium.
There is no magic bullet to solve Blossom End Rot. Treat plants the way they want to be treated (good soil, compost, regular water, etc.), and you should not have a serious problem. But if you do have BER, don’t believe everything you read.
Do Commerical Sprays Work?
A recent study looked at the efficacy of several commercial calcium spray products to reduce BER. This is what they found:
“Sprays of five different commercial preparations containing (Brexil Duo, Calmax Zero N, Ca(NO3)2, CaCl2) or promoting (Greenstim) Ca uptake were tested using BER-sensitive large-fruit variety ‘Beorange’. The experiment was conducted in the commercial greenhouse ‘Getlini EKO’, Latvia, during the autumn–spring season of 2020/2021 under controlled conditions, eliminating the adverse impact of external factors. The results revealed that none of the preparations were effective in increasing Ca content, preventing BER, and did not promote the tomato yield”.
There is no evidence that spraying developed fruit will stop BER. Spraying very small fruit may have some effect, but may take three sprayings to work. They don’t work for two reasons:
- Calcium is not easily absorbed by fruit.
- Calcium is not very mobile. So if it gets absorbed by leaves, it will not be moved to fruit.
Bottom line: don’t use commercial sprays for BER.
I have been looking for information that challenges the BEM and irregular watering story. Back in the 70’s we hacked the soil with deep rototilling, watered by hand using 5 gallon buckets, and you can be sure we didn’t talk about irregular watering. We never saw BEM in tomatoes. Never heard of it. I believe seeds and plants are weaker now, heirloom or not. Who knows what gets done to them. Saving seeds doesn’t solve the problem unless they come from great granny. The soil also does not hold water like it used to. Temperatures vary drastically in the same month. It’s like you have to find a way to create a stable environment for tomatoes as they are getting grouchy from degradation of their environment.
In my experience over many years, it can depend on the variety. Grosse Lisse is very susceptible, which is a pity as they are a great tasting tomato! Irregular watering is the culprit, at least here in southwest West Australia with high summer temperatures drying out our poor soil quickly.
Very true.
Re: Blossom End Rot and Epsom Salts:
We live in central Virginia, in a pocked carved from deep woodlands, with very hard, red brick clay area, with a thin layer of humus on top. (And yes, there are actual brick factories in our area, and have been for hundreds of years) Supposedly, the soils around here are very rich, but almost everyone in our neighborhood gets severe blossom end rot, even if they fertilize. It’s not the mild BER that you describe, but the kind that completely destroys the fruit, leaving nasty black sacks of slime where the tomatoes were. Complete and total destruction of the fruit crop.
Epsom Salt absolutely IS the magic bullet for it. Mix a cup of Epsom salt in a 2-gallon watering pot and shower it all over your plants and in the soil around them, and THAT DAY your blossom end rot will stop spreading. Fruit with beginnings of BER will dry up and finish growing/ripening normally, and you will not get anymore BER for awhile, probably for the rest of the growing season.
My new neighbor who has an organic orchard, and a chemist background grows amazing stuff far beyond my skills or knowledge. He adds and array of natural nutrients, using bio-char as a carrier, various types of compost and other stuff way beyond my understanding. He got the severe BEM like everyone else, but was convinced that it was calcium or other deficiencies. He FINALLY tried Epsom salt, and POOF, it was gone, just like that. Now, he’s on a rant as to what the problem really is, since it can’t be that simple, and he very well may figure it out, but Epsom salt absolutely IS the magic bullet in the short-term, and I have seen no negative effects of using it every year, except the areas where I use it grow everything better, not just tomatoes.
You call Epsom salt use “silly”, but around here, it absolutely works wonders.
Great story – where is your scientific study to show this works?
The science on this is clear. Epsom Salts does not stop BER.
And then there’s the fact that some varieties are more prone to BER. Eg, the plums. I’ve had countless cases of different varieties in the same beds, same soil, same watering, same weather, and BER affecting the plums but none of the others. Always had to assume it’s something genetic.
This link is broken, the one referring to possible effectiveness of foliar calcium sprays. Can you review or update?
Personally I don’t see how these calcium sprays can actually work as claimed.
https://bepls.com/feb_2014/7.pdf
I’ve had issues in the past with BER. About 15 years ago I stopped tilling. Went to a deep mulch, layering method. Only using a broad fork to work the soil. I’ve been using leaves from the yard chopped up, green cut sawmill dust and compost as mulch. I also began using fungi mycelium in the form of shiitake and king oyster mushrooms to break down the woody materials. I’ve not seen BER in 10 years. I don’t water at all, we live in Oklahoma zone 7b. Only water the gardens get is rain.
I’m not botanist or biologist, just permaculture gardener. I do believe there is direct relationship to photosynthetic plants fungi and bacteria that tilling disrupts. Might be an area to further research in future thanks for taking time to read this.
BER has already been studied on a cellar and biochemical level – it is a watering issue.
Could be that the mulch prevents the soil from drying out as much though. Maybe fungi mycelium can also transport water from elsewhere in the soil to the vegetable plant’s roots?
I haven’t had blossom end rot issues with in-ground tomatoes, but did have a problem with container tomatoes, until I added a couple inches of pine needle mulch to the top of the containers, and then the problem went away, and the soil remained moist even if it only received water 1-2 times per week.
Yup – watering is the issue.
Nice article. I have found that my tomatoes and peppers get BER from un even watering. Originally I added calcium but of course that did absolutely nothing. Epsom salts will not help as well but I have had it turn my basil plants from pale to vivid dark green. I also apply it to my peppers and had good results. There may be no science backing this up but it works. There are just a few things like spaying my as tomatoes with aspirin to fend of disease works and again no science. As for BER I put everything on soaker hoses with a timer and topped the garden with mulch…..no more BER!