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How To Treat Blossom End Rot

How To Treat Blossom End Rot

Nothing gives a gardener more pleasure than seeing their plants grow to maturity.

Watching those tomatoes you planted a few weeks ago grow into rich crops for harvesting gives you a sense of accomplishment.

However, disappointment sets in when something goes wrong and your plants don’t grow. You find that they are undersized, yellowing, ridden with disease, or they’re dying.

One of the most typical issues that impact plant health is blossom end rot.

Thankfully, this article will help you identify the early signs of blossom rot, causes, treatment, and most importantly, how to prevent blossom end rot.

What is a blossom end rot?

Blossom end rot is a severe problem that primarily affects fruits and greens. It’s common in tomatoes, cucumber, squash, melons, pepper, and eggplant.

Many new gardeners think that blossom end rot is a fungus. On the contrary, it is mainly an environmental problem.

Blossom end rot is the rotting of the lower end or sides of the plant. This rot ruins the plants by creating a water-soaked area, which is dark brown.

Blossom end rot is primarily a physiological disorder of the plant caused by an imbalance of essential minerals. However, secondary pathogens can also accumulate on the damaged area, causing dark discoloration of the plant.

A plant with blossom end rot isn’t fit for consumption, and you should pull it up and discard it in the trash (not the compost).

The good news is that blossom end rot is not transferable from one plant to another. However, once you notice it in one plant, you should immediately pluck it and throw it away.

The best approach to blossom end rot is prevention. Taking preventive measures saves your precious plants from blossom end rot.

Unfortunately, although not transferable, blossom end rot can affect more than one plant. In severe cases, you can find that almost half of your plants are affected by blossom end rot under the right (or wrong) conditions.

How to recognize it

How to recognize blossom end rot

As mentioned earlier, blossom end rot is environmental, not fungal. Early recognition of the condition might reduce the losses and prevent further damage.

It’s easy to spot blossom end rot. The first sign is a water-soaked area on a plant such as tomatoes. Next, the affected area appears spongy, and it mainly affects the lower end of the plant.

With time, this water-soaked area increases and becomes sunken, leathery, and dark brown. Pathogens continue to accumulate in the affected area, causing complete rotting of the entire tomato.

Note that the top part of the tomato may appear completely normal and healthy, but once you investigate further, you’ll see the blossom end rot.

When you see a black lesion on the rotten part, that’s a sign of advanced blossom end rot.

Although the rot appears typically as one large recessed part of the plant, you may encounter two or three lesions appearing on one plant.

It’s good to check your plant for blossom end rot occasionally. Take walks in the garden and try as much as possible to inspect the plants. While it’s impossible to check each plant, sampling in terms of rows is effective.

For a person with a large garden, inspecting individual plants is a big challenge, so you will need some assistance. However, regular checks of the plant for early identification of blossom end rot are essential for every gardener.

At times, plants affected by blossom end rot tend to hang a bit lower compared to the healthy ones.

They hang lower due to the water-soaked parts, making them heavy. Check plants for low-hanging tomatoes as it may mean that they are sinking from the bottom up.

Most experienced gardeners will immediately identify blossom end rot because they instinctively know that some plants are weak. However, a closer inspection will probably reveal that they are correct and that the cause is blossom end rot.

Causes of blossom end rot

Causes of blossom end rot

As mentioned earlier, blossom end rot is caused by environmental conditions combined with deficiencies of minerals such as calcium.

Many environmental factors also contribute to calcium deficiencies in fruits or veggies.

When you plant tomatoes, they demand a lot of calcium in their early phases of growth and development. This calcium demand is because tomatoes develop rapidly during their initial stages of growth.

Therefore, the absence of calcium can cause the bottom tissues to break down, creating the sunken lesions that you see on plants.

Many people wonder why the bottom point and not the top of the fruit or vegetable is affected. Plants like tomatoes and every other plant start growing from the base, so this is the first area where deficiencies are noticeable.

Calcium deficiencies result from several factors. One factor is that the soil may not have sufficient calcium for the healthy growth of your fruits or vegetables. Calcium deficiency is also common in over-cultivated soil.

Another contributor to low calcium in the soil is inconsistent watering. How does watering relate to calcium in the earth?

A little science will crack this question.

The principle behind the relationship of soil moisture and calcium content in soil is called mass flow. Soil acquires calcium through this process. As a result, water is rich in many dissolved nutrients–21% of calcium molecules for every mass of water crystallization.

Water is the primary source of calcium for soil. Soil acquires the calcium from water which is absorbed by the plant’s roots. So, insufficient watering of plants means that there’s little calcium absorbed by the roots leading to blossom end rot.

Container-grown tomatoes are the most vulnerable to developing this condition, especially when rainfall is inconsistent.

This is because plant roots cannot penetrate deep into the natural soil core to get sufficient calcium, and there isn’t enough in the top soil layers. The outcome is that your plants suffer and die from insufficient calcium uptake.


Since fungi or insects don’t cause blossom end rot, you cannot use fungicides or insecticides as a treatment. Moreover, blossom end rot is not treatable per se but preventable.

Signs of blossom end rot in one or two fruits or vegetables mean that there’s a need to take preventive actions to protect the plants around the affected area.

Treatment involves adding as much calcium to the garden as possible. A calcium solution is the best treatment method for low calcium deficiency. In addition, early identification of blossom end rot increases the efficiency of treatment using a calcium solution.

Other sources of calcium, such as garden lime, save the rest of your harvest from blossom end rot.

Spreading a handful of garden lime by sprinkling over the soil surface and digging it into the dirt is an excellent treatment. The garden lime will settle in and be absorbed by the soil.

In severe conditions, use tougher treatment methods such as spraying a rot stop solution. This works best for various fruits and vegetables like melons, cucumbers, tomatoes, and peppers.

All the treatment methods above are appropriate for correcting calcium deficiency in the soil. However, ensure that you always use the prescribed amounts of different solutions to avoid creating more damage.

For example, solutions such as rot stop have foliar fertilization, so using an excessive amount may cause more harm to your plants.

Is there a way to prevent it?

Is there a way to prevent it?

The best approach against blossom end rot is prevention. Treatment methods are suitable for saving the rest of the harvest after the damage has already been done.  

The idea is to ensure that plants always have sufficient calcium. This is achieved through proper watering–not overwatering! Consistent watering of the garden ensures a mass flow for soil to acquire calcium from the water.

Ideally, plants need at least a one-inch source of water per week for healthy growth. This water level allows an efficient mass flow process.

Contrary to daily watering, we recommend watering your garden weekly using a steady soak and slow-motion watering near the roots. This method ensures that there’s efficient penetration of water into the soil and better saturation.

Apart from the above solutions, here are some specific preventive measures against blossom end rot:

  1. Early and proper mulching: It helps in retaining soil moisture and reduces weeds.
  2. Maintaining suitable garden pH: Ensure that the soil pH is at 6.5 before planting. Use a soil pH meter to determine the level before taking corrective action. Calcium and other nutrients thrive at this pH level.
  3. Maintaining the proper temperatures: For indoor planting, maintain a temperature of 600F.
  4. Avoid excessive fertilization: Excess fertilizers create a pH imbalance in the soil. Calcium and other minerals do not overcome an imbalance in pH levels that are too high or too low.
  5. Use good soil for indoor and container plants.
  6. During winter, ensure that the soil is warm enough before you commence planting.

Follow these steps to help you overcome the risks of blossom end rot.

Consider keeping continuous records in your garden to identify crop varieties that are more susceptible to blossom end rot and make the necessary adjustments.


It’s painful to see your expectations for a plentiful harvest go down the drain thanks to blossom end rot. Unfortunately, this condition is a menace to many gardeners because it ruins your plants and hard work. 

But prevention is known to be better than cure, and now you know how to save your plants from blossom end rot.

Take the necessary measures to protect plants from this condition so that you can enjoy the fruits of your harvest.