If there are plenty of rainy days after the growing season where you are begins then those rainy days shift over to dry at the time your tomatoes are setting, be on the lookout for blossom-end rot (BER).

The damage can start to occur when your tomatoes are approaching halfway to maturity. The damage appears in the form of large water-soaked parts that turn leathery to the touch and dark brown in color. The area is rotting so the fruit must be discarded.

The spots that appear to be water-soaked occur at the end where the blossom is which is the bottom side of the fruit. This is why it’s called blossom-end rot.

Rather than being a disease, blossom-end rot is a physiological disorder. It’s brought about by an imbalance of calcium within the plant. It’s a common problem in tomatoes, but not only tomatoes. It also occurs in squash, melons, eggplants, peppers, and cucumbers.



Blossom-End Rot Causes and Symptoms

Where there’s a calcium deficiency in the soil you’ll find that blossom-end rot is commonplace.

What causes a calcium deficiency in the soil?

Bad drainage. A soil that’s depleted. Calcium displacement.

Fortunately, a deficiency of calcium in soils is not a frequent problem. But then it’s not the single reason for blossom-end rot.

What else causes blossom-end rot?

  • Overwatering
  • Uneven watering (frequently because of drought)
  • Heavy rainfall
  • Root damage brought about by cultivation
  • Cold soil
  • Soil pH that is too low or too high
  • Temperatures that rise quickly
  • High salt levels in the soil
  • Too much nitrogen in the plant during its early life cycle which causes too rapid growth

But still, right at the root of the issue is the lack of calcium. And this is because all of the above environmental concerns mean that your plants are not able to absorb calcium at a pace that is rapid enough to keep in pace with the fast growth. Either that or the plants have problems processing the calcium. This means even though they do take up calcium the plants are stressed due to environmental conditions and thus cannot process calcium.

Typically, blossom-end rot occurs whenever the fruit is ripening or it’s green. It starts with a small, water-soaked area that is depressed at the fruit’s underside.

The fruit gets larger, the water-soaked area becomes more depressed, it turns leathery brown or black.

If the level of calcium is too low to support healthy fruit growth, the plant tissues begin to break down. This causes the rot.

But if you do see it early on – the blossom-end rot – some of the fruit can be salvaged if you wish by cutting around the part that’s rotten.



How to Control and Prevent Blossom-End Rot

You can’t really control blossom-end rot once it’s taken hold of a particular tomato. The only thing to do is to remove the fruit from the bush.

If you remove the fruit there is a possibility that in its place will grow a healthy fruit.

Make an application of a liquid calcium fertilizer when removing affected fruit. This will encourage healthy tomatoes to grow.

What about protecting against blossom-end rot?

As is often the case, the best way to protect is to prevent.

Here are a few blossom-end rot prevention tips:


  • Don’t hoe near the root system. You don’t want to damage the roots.
  • During the early fruiting phase, don’t over-fertilize.
  • Retain the soil pH at 6.5 or thereabouts. If need be, add lime. This will increase calcium ratio in the soil.
  • Add bone meal, gypsum, or powdered milk to the hole you dig when transplanting your tomato plants. This will encourage calcium uptake via the roots.
  • Crushed eggshells in the bottom of the hole also works. However, eggshells take some time to break down so they are a better long-term fix.
  • Shop-bought calcium sprays may be applied in direct fashion to the plant foliage once the blossoms start to appear.
  • Maintain a consistent water supply through mulching and manual irrigation (as and when required). If it rains heavily ensure there’s good drainage. Let the soil dry out between manual waterings. The ideal scenario would be to provide your tomato plants with about an inch of moisture weekly.
  • Don’t use an ammoniacal nitrogen fertilizer. Instead, use a nitrate nitrogen fertilizer. If you use ammoniacal it can encourage blossom-end rot.



Blossom End Rot FAQs


Can blossom-end rot be stopped?

Yes. If appropriate treatment is given you can stop blossom-end rot and possibly even reverse it. Once affected, individual fruit cannot be salvaged. But the plant’s health can be improved. Here are the steps needed to stop blossom-end rot.

1. Discard all fruits that have been affected. Add powdered milk to the watering ‘system’ – the water used to hydrate your plants. This will give them a nice jolt of calcium. The addition of eggshells does work but it takes time to break down eggshells. So it’s not fast enough unless the eggshells are added to the base of the hole used when transplanting your tomato plant seedlings.

2. As a way to prevent blossom-end rot, use a fertilizer that is low in nitrogen but has a high level of superphosphates (good for root growth). For example, a fertilizer with an N-P-K ratio of 5-20-5 or 4-12-4 is good.

3. Your plants need a lot of water and on a schedule that is consistent. Inconsistent watering regimes can cause blossom-end rot. So, that said, water your plants on a daily basis. If it’s particularly hot or you reside in a hot area you can up that watering schedule to twice daily. Water your plants six inches deep into the soil. For healing to occur it can take a few weeks of persistent hydration.



Is there a blossom end rot spray?

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Yes, there is, though it’s not much other than a corrective-type spray – correcting low calcium levels in particular. 

It’s called Rot-Stop.

As mentioned, Rot-Stop corrects a deficiency of calcium within the tomato plant.

The calcium comes in the form of calcium chloride in terms of it being the main active ingredient. 

Rot-Stop is easy to apply. Simply mix it together with water and use a tank sprayer or hose-end sprayer to make the application to the foliage. Spray the foliage until you witness run-off. 

Don’t use Rot-Stop as a base fertilizer. It’s excellent for calcium addition, but it will not provide all plant nutrients. 

You can use Rot-Stop with tomato plants, cucumbers, peppers, melons, and more. 

Does, Rot-Stop really work? 

Yes, user feedback is excellent. It – Rot-Stop – offers a successful way to halt blossom-end rot in its tracks, or to stop it from occurring in the first place. 

Rot-Stop Calcium Fertilizer

for Halting Blossom-End Rot in its Tracks!

Can overwatering cause blossom-end rot?

Overwatering or under watering tomato plants can bring on blossom-end rot. In other words, at least where watering is concerned there’s a lack of consistency.

Likely tomato plants that are suffering from blossom-end rot were not watered enough. After this, and as a way of correcting the issue, the plants were overwatered.

There is a further scenario. If the growing season is very wet to start out and when the fruits are beginning to set, the weather changes and turns dry. In which case, there’s an inconsistency with water content and not enough soil-based calcium.

How can blossom-end rot be treated?

Don’t allow the soil to dry out completely at any time. Water your tomato plants every day. If it’s particularly warm weather or you reside in a hot area water twice each day.

Add a layer of mulch around the base of your tomato plants. The mulch will help to retain moisture in the soil.

Lack of calcium? If the soil is lacking calcium mix powdered milk in with the water you’re using for your tomato plants.

With powdered milk you get an immediate calcium boost.

Either this or nourish with a low nitrogen fertilizer which is high in superphosphate. N-P-K ratio of 5-20-5, 4-12-4 or something similar is ideal.



Can you eat tomatoes with blossom end rot?

Yeah. Just cut out the bad bit. You may find that tomatoes that have succumbed to blossom-end rot are not so pleasant to the taste and have an odd texture. 

Anyway, eating fresh is fine. Don’t use tomatoes that have been affected by blossom-end rot for canning or any other types of preservation. 


How to prevent tomato blossom end rot

Does blossom end rot impact the entire plant?

Only the fruit, not the entire plant. Though that’s simplifying the matter. 

It’s on the fruit that you see blossom-end rot. Nevertheless, blossom-end rot can be caused due to root-located issues.

If the root system is underdeveloped it may not be able to draw in the required amount of water and calcium. Not enough water and calcium can equate to blossom-end rot. 

So the symptoms of blossom-end rot are seen in the fruit but the disorder impacts the entire plant. 


Will adding Epsom salt stop blossom end rot?

No. In fact, adding Epsom salt can make blossom-end rot worse. 

Blossom-end rot is caused by inconsistency with respect to water as well as not enough calcium. Epsom salt does not consist of any calcium. 

Rather, it consists of magnesium sulfate. Magnesium ions ‘fight’ with calcium ions as to which will be taken up by the root system. 

So rather than adding Epsom salts, use powdered milk instead as this adds calcium. And ensure that your watering regime is very consistent. 



Can blossom-end rot be prevented?

Prevention of blossom-end rot can be accomplished through a watering schedule that is consistent and making sure there is copious amounts of calcium in the soil. 

If where you are is cold when you wish to plant your tomatoes out, wait until the soil warms up and then plant. Colder soils may halt your tomato plants from getting sufficient nutrients in through the root system.

Your soil should be around 6.5 in terms of pH – slightly on the acidic side. 


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