How To Stop Blossom End Rot

Your tomato plants are tall and green; you’ve taken the time to carefully stake or cage them to support their growth. Right now they are loaded with tons of green tomatoes, and some of them are just starting to blush red. And then three days later, it all goes horribly wrong.

There is nothing more disheartening than to see that all of your ripening tomato beauties (or peppers or squash) are now rotting from the bottom—right on the vine!

What is Blossom End Rot?

Blossom-end rot looks like a discolored, watery, sunken spot at the blossom end of the fruit, most commonly tomatoes. The spot will start out small, and grow larger and darker as the fruit continues to grow.

Blossom-end rot can quickly cover half the fruit, making it totally inedible. Secondary diseases or mold can also form on the affected areas, overtaking the entire fruit.

Blossom-end rot is more common if you planted in cold soil or when your garden experiences extremes in soil moisture levels—either too dry or too wet.

What Causes Blossom End Rot?

Blossom-end rot is a disorder caused by calcium deficiency in the plant.

While this may be a result of low calcium levels in the soil, more often than not, it is the result of erratic watering.

When the plant is allowed to get too dry, or is given too much water over a period of time, its ability to absorb calcium from the soil is greatly diminished. In other words, your soil might have plenty of calcium, but it just isn’t bioavailable and being taken up and utilized by the plant.

If your soil is indeed low in calcium (determined by a soil test) the easiest solution is to add garden lime several times per year, according to the directions on your soil test results. (Don’t just add lime without testing your soil first, as you might disrupt the optimal pH for growing your crops.)

Over fertilization, especially with high nitrogen fertilizer, can also cause blossom-end rot. Over fertilization can cause such rapid growth that nutrients such as calcium won’t be able to keep up with the growth. Always soil test before fertilization and fertilize according to the results.

You can also choose varieties of tomato that are resistant to blossom-end rot. Varieties of tomatoes that produce large fruit tend to be more susceptible to blossom-end rot, while varieties with smaller fruit are less likely to suffer it.

Blossom-end rot is much easier to prevent than it is to cure. Once it has set in, it can be really hard to reverse, but there are a few things you can do that have a good chance of turning things around.

Ensure Consistent Water Supply

If the issue is erratic moisture, here are some tips:

1. Make sure your soil isn’t allowed to dry out. The best defense against blossom end rot is a nice, consistent soil moisture level.

2. As the summer rolls on, it is easy to forget to water the garden regularly. If it is hard for you to be consistent, or if you plan to take a vacation, consider installing a drip irrigation system and a timer. Drip irrigation is a major time-saver, affordable, water-wise and an outstanding disease prevention method because it both keeps soil moisture regular and keeps water (and therefore fungus spores) from getting onto the leaves of your crops.

3. Mulch. By adding a three-inch layer of organic mulch, you can help maintain adequate soil moisture levels, even during dry spells. It is best to add the mulch after your soil has warmed in the spring.

4. Plant susceptible crops (such as tomatoes, melons, squash, peppers, and eggplants) in well-drained soil that has been amended with compost or well-rotted manure. Soil amended with plenty of organic matter will retain moisture better and supply plenty of nutrition (including calcium) to your plants.

Fortify Your Crops at Planting

In addition to making sure you have consistent moisture levels in your soil, you can fortify your plants when you put them in the ground to make sure they get plenty of calcium throughout the season.

Many people use garden lime to adjust their garden pH and add calcium at the time of planting. This will treat the entire garden soil. (If your soil pH doesn’t need adjusting, use gypsum instead of lime.) You can also add 2-3 Tums tablets or other calcium carbonate antacid to each planting hole to add extra calcium.

I personally like to use a teaspoon or two of eggshell calcium to each hole as I plant my tomatoes, peppers, squash, etc. This is a great way to use up a common food waste product. Here’s how to make it.

You can also use commercially-available, Calcium/Magnesium fertilizers made for tomatoes at planting and throughout the growing season.

If you already have signs of blossom-end rot, you can make a solution from calcium carbonate antacid tablets, milk and water, and irrigate your plants with it daily to help keep blossom-end rot from destroying more of your crops than it has to. This might help turn things around, but isn’t foolproof.

Don’t bother with the calcium leaf sprays at the garden store that promise to stop blossom end rot. While they can help with other issues related to nutrient deficiency, to stop blossom end rot, the calcium has to come up from the soil through the roots, not through the leaves.

Prevention is really the cure here.

Preventing Blossom End Rot is the Best Cure

Good, fertile soil and consistent watering can make all the difference in stopping this heartbreaking problem before it starts and ruins your crops. Get your soil tested each spring, and amend it accordingly.