Blossom End Rot (BER) is a disfiguration found in fruiting vegetables, like tomatoes. It also affects peppers, watermelons, egg plants 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 web sites, 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 plants 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 it’s 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 had low calcium levels.
More recently, scientists have had a closer look. It turns out 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.
In the case of Blossom End Rot, the transporter compounds are just not moving enough calcium to the growing fruit.
You might be thinking to yourself that BER is a calcium deficiency, but that is not correct. The rest of the plant can have lots of calcium and BER can still develop. Compare this to a serious earthquake. The thing the affected people need most urgently is drinking water–they have a shortage. We don’t have a global shortage of drinking water–we just don’t have it in the right place at the right time.
Once you understand the real problem, it becomes obvious why many of the remedies for BER don’t work.
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 of calcium, and if this is the case fertilizing with calcium will 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 exasperate the problem by making it harder for the plant to absorb calcium. For example, excess ammonium from of nitrogen can make it harder for the plant to absorb calcium.
2) Spray calcium fertilizer on the leaves ie foliar feed.
First of all foliar feeding is not a very good way to get nutrients into a plant–it is just not very effective. (corrected Aug 2014 –see comments) First of all, foliar feeding is not a good long term solution for feeding plants, at best it is a quick fix solution. But let’s assume the leaves do absorb calcium. This will not help much because the transporter compounds are not working properly and secondly, calcium absorbed by the leaves will not be moved to the fruit. A quote from Dr. Linda Chalker-Scott, “What is well known is that Ca only moves in the plant via the xylem and moves with the transpirational water flow 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. ”
This means that none of the foliar sprays, or Blossom End Rot sprays on the market work for 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 is 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 over water.
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 of 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 serious problem. But if you do have BER, don’t believe everything you read.
1) Blossom End Rot by RHS: http://rhs.org.uk/advice/profile?pid=395
2) Why Calcium Deficiency is Not the Cause of Blossom End Rot in Tomato and Pepper Fruit: http://www.sciencedirect.com/science/article/pii/S0304423814002830
3) de Freitas, Sergio Tonetto; Mitcham, Elizabeth Jeanne; Jiang, Cai-Zhong. 2012. Mechanisms Involved in Calcium Deficiency Development in Tomato Fruit in Response to Gibberellins. Journal of plant growth regulation, v. 31, no. 2, p. 221-234
4) Ho, L. C.; White, P. J. 2005. A cellular hypothesis for the induction of blossom-end rot in tomato fruit. Annals of botany, v. 95, no. 4, p. 571-581
5) Blossom End Rot – Transport Protein Identified: http://phys.org/news/2011-11-blossom-protein.html
6) Photo Source: NC State University