Blossom End Rot in Tomatoes: How To Prevent It

Blossom end rot is a common problem with tomatoes and other vegetables that grow in the ground. The ends of the fruits start to rot and turn black.

There are a few things you can do to help prevent end rot from happening, or to fix it if it does happen.

two harvested tomatoes
two harvested tomatoes

While I’ve never had much luck trying to reverse blossom end rot once it sets in, I now follow these simple tips (detailed below) and haven’t had a problem with this condition on my tomatoes since.

Though difficult to fix, blossom end rot is easy to prevent.

Keep reading for more information!

What is Blossom End Rot?

Blossom rot, or blossom end rot, is a common problem encountered by tomato gardeners. The condition is characterized by a dark, rotten spot at the blossom end of developing tomatoes.

Fortunately, there are ways to combat blossom rot before it starts, but once it appears on an individual fruit, there is no way to “cure” the affected tomato.

Although you can cut away the rotted portion and safely eat the rest, it is best to eliminate the problem before it reaches that point.

How does blossom end rot start? Blossom end rot first presents as a dime or quarter-sized dark brown or black spot on the end of the tomato opposite the stem.

Unfortunately, you may find this small blossom end rot spot signifies that the tomato is totally rotted out inside. Unchecked, you can lose a large portion of your entire tomato crop to this condition.

What Does Blossom End Rot Look Like?

The symptoms of blossom end rot are easy to spot: the fruit develops a dark, leathery patch on the blossom end (the end opposite the stem).

To quickly summarize, blossom end rot presents the following symptoms:

  • Blackening and rotting of the stem
  • Dark spots on the skin of the fruit
  • Sunken spots no the fruit
  • No damage to leaves, stem, roots, or other plant parts
  • Typically affects the first flush of fruits for the season only

The first signs of blossom end rot are small, dark spots on the skin of the fruit. These spots eventually enlarge and turn brown or black, causing the fruit to rot from the inside out. Blossom end rot is most commonly caused by a lack of calcium in the soil.

As the fruit begins to grow, the lack of calcium prevents the formation of strong cell walls and plant tissues, leading to the development of the dark spots.

Blossom end rot is not a bacteria – it is a physiological disorder. It affects only the develoing fruit and again, is caused by a lack of sufficient calcium. It does not affect the leaves or impact fruit set – it just affects maturing fruits.

What Causes Blossom End Rot?

Blossom end rot is a common problem encountered by gardeners, especially those who grow tomatoes.

The cause of this condition is a lack of calcium in the fruit. Calcium is necessary for the formation of cell walls, and when it is absent, the fruit begins to break down.

Blossom end rot is often the result of inconsistent watering.

When the soil is too dry, it prevents the roots from taking up calcium from the soil. However, overwatering can also lead to blossom end rot by leaching calcium from the soil.

Are Tomatoes the Only Plants That Get Blossom End Rot?

Blossom end rot is a common problem for gardeners who grow tomatoes.

However, this common disease is not limited to tomatoes; it can also affect peppers, squash, cucumbers, eggplants, watermelons, and other cucurbit crops.

Preventing Blossom End Rot

How can you prevent blossom end rot in the first place?

Eliminate Calcium Deficiencies

What causes blossom rot to start is a deficiency in calcium. In order for tomato plants to grow their fruit properly, they need sufficient calcium.

Even if you have plenty of calcium in your soil, your plants may not be able to effectively absorb it for a number of reasons. When this occurs, your plants are at risk of contracting blossom rot.

Therefore, the way to prevent this tomato disease is to ensure your plants have access to enough calcium and are able to absorb it appropriately.

Test the Soil

Before you plant your tomatoes, be sure to have your soil tested or do it yourself with an inexpensive soil testing kit. Ideally, your soil should be slightly acidic, with a pH somewhere between 6.0 and 6.8.

If your soil is too acidic, you can add some limestone or lime to increase the pH. Use caution when adding these amendments, however. If you add too much, you’ll end up with soil that is too alkaline.

If your soil is naturally alkaline, you can amend it with rich organic matter, such as chicken manure that is well composted. It can be very challenging to lower soil pH, however, because limestone in the ground is continually dissolving.

If you live in an area where alkaline soil is a fact of life, you may want to build raised beds to create a more hospitable growing environment for your plants.

Use a Balanced Fertilizer

While there are many possible causes of this tomato disease, one of the most common is an imbalanced fertilizer. When fertilizing your plants, be sure to use a balanced fertilizer that contains both nitrogen and calcium.

This will help to ensure that your plants have all the nutrients they need to stay healthy and prevent blossom end rot.

You should also avoid over-fertilizing, as this can lead to a build-up of salts in the soil that can damage roots and prevent calcium from being absorbed.

Make Sure the Soil is Warm But Not Too Hot

While this tomato disease can be caused by a number of factors, one of the most common is fluctuations in soil temperature.

If the soil is too hot or too cold, it can prevent the plant from getting the calcium it needs. As a result, it’s important to make sure that the soil is warm but not too hot before planting tomatoes.

Use Mulch

Mulch helps to regulate moisture levels in the soil, preventing the roots from becoming too dry. It also helps to prevent weeds from competing with plants for nutrients. As a result, mulch can be an effective tool for preventing blossom end rot.

In addition, mulch helps to insulate the soil, keeping it cooler in summer and warmer in winter. This consistent temperature helps to promote root growth and prevents stress on plants.

Be Careful Working Near the Roots

Avoid disturbing the roots when working in the garden, and particularly any cultivation around the tomatoes, as this can damage the roots and prevent them from taking up nutrients effectively.

Choose Resistant Varieties

While there are a number of ways to prevent this frustrating problem, one of the best is to choose resistant varieties.

These varieties have been bred to be more tolerant of calcium deficiencies, and as a result, they are much less likely to experience blossom end rot.

If you’re concerned about this problem, be sure to ask your local nursery for some resistant varieties that will do well in your area.

Stake Tomato Plants When Young

Blossom end rot is a common problem for tomato growers, but it can be prevented by staking tomato plants when they are young.

Staking tomato plants helps to prevent this common disease by keeping the fruit off the ground and allowing the plant to get more air circulation.

This helps to regulate moisture levels and improve calcium uptake. In addition, staking tomato plants makes it easier to water them deeply and evenly, which also helps to prevent blossom end rot.

And if you do it when the plants are young, you don’t have to worry about damaging the plant (particularly its roots) which can worsen the problem of blossom end rot.

Keep Good Garden Records

Any gardener worth their salt knows the importance of keeping good records. By tracking what you plant and when, you can ensure that your plants are getting the nutrients they need to thrive.

You can also avoid problems like blossom end rot, which is caused by a lack of calcium in the soil.

I’ve found that recording my observations in the garden each year has made a huge difference in terms of disease prevention, pest control, and all kinds of other problems.

You don’t need to write a novel, either – just keep a few notes of what worked well and what didn’t so you can refer to it next year.

Don’t rely on your memory alone!

By keeping careful records, you can spot trends and make adjustments to your gardening methods accordingly. So don’t be afraid to break out the notebook and start jotting down some notes.

Water Regularly and Consistently

tomato starts

Once your soil is at the optimum pH level, you’ll want to ensure your plants are receiving enough water on a consistent basis.

Optimal tomato growth requires regular and deep watering so that water gets all the way down to the entire root system.

Tomatoes won’t flourish if you allow them to go dry between watering sessions.

They certainly won’t thrive if they are being grown in drought conditions! They need that soil moisture.

So, be sure your plants receive 1 to 1.5 inches of water per week, but don’t go overboard and give them too much.

Fortunately, blossom end rot usually shows up at the very beginning of the season as first fruits appear. If you notice your tomatoes are showing possible signs of blossom rot, make sure your plants are watered deeply every 4 to 5 days.

If it is extremely hot in your area, water them even more frequently. To determine when it is time to water your plants, dig down 3 or 4 inches into the soil.

If the soil is moist, wait 24 hours and check again. When the soil at that level is dry, it is time to water again.

Does Blossom End Rot Spread?

While blossom end rot does not affect the taste of the fruit, it can make it unsightly and unappetizing. The good news is that this frustrating disease is not contagious; it cannot spread from one plant to another.

However, once a plant has been affected, it is likely to experience the disorder again in future growing seasons.

As a result, gardeners should take steps to prevent blossom end rot from occurring in the first place.

By ensuring that plants have access to adequate calcium and maintaining proper moisture levels, you can help keep your fruits and vegetables looking and tasting their best.

Getting Rid of Blossom End Rot

You found your tomatoes have those black spots! Here’s some help on how to fix blossom end rot:

Using Liquid Kelp Extract

While there are several chemical treatments available, many gardeners prefer to use liquid kelp extract as a natural remedy. Kelp is a type of seaweed that is rich in minerals, including calcium.

When applied to the soil, kelp extract helps to correct the calcium deficiency and prevent blossom end rot. In addition, kelp extract also provides other nutrients that are essential for plant health.

Remove All Affected Tomatoes

Be sure to remove all affected tomatoes from the plant. Although blossom end rot doesn’t spread or jump from plant to plant, there’s no sense in leaving affected tomatoes on the vine.

Often, I’ve found that this common disease only occurs in the first flush of fruit for the season. In later crops, the problem goes away as the plant matures.

Removing the affected fruits will allow your tomato plants to spend their energy on forming new, healthier fruits instead of nurturing unhealthy ones.

Water With Powdered Milk (Maybe)

A common tactic to remedy rot is to try adding powdered milk to the water. Gardeners who have tried this method report that it works well, and that the plants are less likely to develop rot.

There’s not a ton of science behind this method, and most scientists argue that it won’t work well because the calcium needs to be in the soil prior to growing the tomatoes – they won’t absorb any new calcium you add.

However, many people report that, anecdotally, it works. While it wasn’t effective for me when I tried it out, it’s worth a try!

As with any gardening technique, it is important to experiment to see what works best for your particular plants.

Try Epsom Salts

Make a blossom end rot spray with 1 cup Epsom salts and 4 cups water-carefully spraying the soil until damp.

Make sure your soil has plenty of calcium when planting-add an eggshell to the hole you dig when you go to plant the tomato plant. Go down an extra inch, add the shell, cover with dirt, then add the tomato plant. This will help add calcium as the egg shell composts.

Can You Eat Tomatoes with Blossom End Rot?

A common question is “Can you eat tomatoes with blossom end rot?”

Yes you can eat tomatoes that have this common disease. Simply cut the dark spots away, and use in salsas, soups, sauces, or when canning.

Although blossom end rot can be a challenging garden dilemma, a little preparation and planning will go a long way towards banishing it from your garden.

Keep this information in mind when planting your tomatoes this year, and consider using a calcium supplement or organic mulch to help reduce the incidence of this disease.

With a little bit of effort, you should be able to have a bountiful tomato harvest free from blossom end rot.

updated 07/11/2022 by Rebekah Pierce

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