Blossom-End Rot: Symptoms, Treatment, and Control

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blossom-end rot

Do you know that your plants can have Blossom-end rot due to lack of calcium and/or underwatering?

Blossom-end occurs on both green and ripe fruits.

You can identify it by water-soaked areas that tend to gradually widen and mature into sunken, brown, leathery spots on the bottom end.

In most cases, secondary pathogens tend to appear, like black, fuzzy-like growth that can attack the affected area and cause complete rotting of the fruit.

Moreover, blossom end rot does not spread from one plant to another.

It is important to note that this is a relatively common garden problem, and is not a disease.

In most cases, this problem affects pepper, squash, cucumber, and melon fruits, as well as tomatoes.

This is most common when the growing seasons begin out wet and then become dry when the fruit is setting.

Damage first appears when the fruit is about half of its size and eventually begins to rot, thus, pick and discard the fruit.

Keep on reading to learn more about this problem in detail.

Causes of Blossom-End Rot

Fortunately, blossom end rot does not occur due to any disease or pest.

Instead, it results due to a lack of calcium in your plants. This lack of calcium can occur due to low calcium levels in the soil.

Or in most cases, due to soil that is either over or underwatered.

When there are wide fluctuations in the soil moisture, this leads to a reduction in the ability of your plants to take up calcium from the soil.

Moreover, when the demand for calcium exceeds the supply, the tissue in the fruit breaks down and the blossom-end rot occurs.

In addition to issues of watering, calcium deficiency during fruit formation can occur due to a number of factors.

blossom-end rot identification

These causes are:

  • too much nitrogen-heavy fertilizer
  • improper soil pH
  • high salt levels in the soil
  • damage to the roots of the plant

Therefore, be aware of these causes when caring for your plants.

This is especially for tomatoes and other plants to prevent blossom-end rot.

It is important to note that some blossom-end rot is more or less normal in the first tomatoes of the season since the plants are often under stress during the initial set.

It also tends to occur more often in plants that you grow in containers as the soil is more susceptible to fluctuations in moisture.

In other words, the plants dry out too much and their fruit is affected as a result.

In case the damaged portion of the fruit is small, you can trim it off and enjoy the rest of the fruit.

Soil Moisture and Calcium

Unlike other plant nutrients which cone into the roots of the plants through diffusion, calcium comes into the plant through the process of mass flow.

Mass flow occurs when water carries dissolved nutrients in the root of the plant.

This means that calcium primarily comes via the water your plant absorbs.

However, if there is not enough water coming into the plant, it is unable to get the calcium it needs, even if there is plenty of calcium in the soil.

As a result, the plant begins to show signs of calcium deficiency.

It is important to note that calcium deficiencies are unusual in a garden setting.

Moreover, the calcium is likely in the soil and plants are unable to access it unless they have ample and consistent water.

The same goes for pants that you grow in pots, specifically when you grow them in commercial potting soil along with added fertilizer or potting soil mixed with compost.

The calcium is there, however, your plants are not just getting it.

Blossom-end rot is especially common in container-grown tomatoes or during years of inconsistent rainfall.

Furthermore, when your plants are subjected to dry periods, the calcium is unable to move into the fruits where it is needed for proper growth.

Thus, it leads to a calcium deficiency and blossom end rot.

Identifying Blossom-end Rot

In most cases, blossom-end rot appears while the fruit is still green or ripening, so it often affects the first fruit that forms on the plant.

Moreover, blossom-end rot can start with a small, depressed, water-soaked area on the blood end of the plants, i.e. the bottom, opposite stem.

The spot starts off looking like a dark bruise and as it changes, it becomes sunken and turns black or dark leathery brown in color.

Half of the fruit may eventually be affected as a result.

Prevention Tips

Fortunately, blossom-end rot is preventable.

With the help of consistent soil moisture, you can effectively prevent this disorder.

However, make sure to regularly water your plants during periods of dry weather.

Moreover, there needs to be around at least one inch of water per week and it is much better to apply that full amount of water all at once.


You can do it through a slow, steady soak to the root zone of your plants.

Applying a little are every day or every few weeks only makes the problem to be worse as that water is unable to penetrate down into the soil to saturate the entire root zone.

Keep in mind that the calcium in the soil is not always right next to the roots of the plants.

it may need to travel some distance to enter the plant with soil moisture.

Other Tips

Some other tips are:

Aside from watering your plants consistently and properly.

The following are a few other things you can do to prevent blossom end rot:

Mulch early and correctly: Add a layer of 2 to 3 inches of organic matter to the top of the soil around your plants early in the season.

This will help to keep the soil moisture levels even.

Moreover, you also need to reduce weed consumption as well.

Some good mulch options are:

  • straw
  • untreated grass clippings
  • shredded leaves

Make sure the soil Ph of your garden is as close to 6.5 as possible: With proper pH of the soil, it can help your plants with calcium uptake.

At that, pH levels, calcium, and different other nutrients are more readily available for plant use.

Avoid Over-Fertilization: Make sure to avoid synthetic chemical fertilizers.

For instance, you can feed your tomato plants with ammonia-based nitrogen fertilizers that are unable to uptake calcium as well because the excess ammonium ions can interfere with the availability of calcium.

You can, however, feed your plants:

  • fish emulsion
  • compost
  • liquid kelp
  • seaweed emulsion
  • a balanced organic granular fertilizer

Special Considerations for Plants in Containers

Blossom-end rot tends to be especially problematic when you are growing plants in containers.

This is because they are often left to dry out in between watering, or they are not watered as deeply as they should be.

The following are a few tips to prevent blossom-end rot in pots:

Make sure that your plants, either tomato, pepper, zucchini, etc. are growing in a pot that has the ability to hold a minimum of 5 gallons of potting soil.

The bigger the pot, the bigger its roots system, and the healthier your plant will be.

Moreover, each container should also have drainage holes in the bottom.

Proper watering does not mean to add a little water to your pots every day.

it rather means that you use a hotel to thoroughly saturate the soil every two to four days.

For instance, you can add 3 to 5 gallons of water at minimum to each of your tomatoes every few days throughout the growing season, somewhere there rainwater is unable to reach them.

special considerations

As long as the pot has a drainage hole, and is not sitting in a saucer full of water, it is nearly impossible to overwater them.

Deeper, less frequent irrigation is always better than adding a bit of water every day.

In case you plant your veggies in a commercial potting mix, it is important to note that there may be little or not enough calcium present.

It also depends on the mix.

To mak sure there is amply calcium, always mix your potting soil, half-and-half with compost.

Furthermore, compost contains a blend of macro and micronutrients and helps to support good vegetable growth.

Also, it increases the water-holding capacity of the potting soil.

Another option can be to mix a half-cup of organic-based granular fertilizer into the potting soil/compost blend at the start of the season.

Fixing Blossom-End Rot

In case your plants already have a few fruits with black cankers, it is not too late to reverse this disorder for the rest of the growing season.

You can change your watering habits.

Make sure to water deeply and less frequently. Remember, that plants like tomato vines need at least an inch of water every week.

Thus, if you do not get enough rain, you will have to apply water from the hose or a sprinkler.

In case you are using a sprinkler, set an empty 1-inch tall tuna in the pat of the sprinkler near the plants that have blossom-end rot.

blossom-end rot 1

When the can fill to the top with water, you can apply an inch of water.

However, it is important to note that every sprinkler is different. Some can fill the tuna can in 40 minutes while others may need to run for 3 hours or more.

Moreover, water in the morning whenever possible as that the foliage dries before nightfall.

Consistency is the key and does not let your plants go through periods of drought, even if it is just a few days.

The existing cankers will not go away, and you can discard those fruits.

With proper watering and an added layer of mulch, however, new fruits will develop with no signs of rot through the rest of the growing season.

Final Thoughts

There may be many end rot remedies you hear about blossom-end rot, but certain remedies that involve antacids, crushed eggshells, and milk sprats are not viable solutions to this problem.

Instead, make sure to focus on getting enough calcium that is already present in the soil of your water into the plants by watering them consistently. Moreover, it is important to remember that there is no ‘miracle fixes’ for blossom-end rot.

The only time you should add calcium to the soil is if the soil test tells you that there is a true deficiency in your plants.

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