Most vegetable gardeners have dealt with blossom end rot. It’s a very frustrating problem to have. One day you’re walking through your tomato patch admiring your first plump green tomatoes and suddenly you notice that some are developing a brown mushy bottom.
Tomato blossom end rot is most commonly seen on young plants and starts as a brown or black spot on the blossom end of the fruit. The spot will usually get larger and continue to rot if the fruit is allowed to remain on the plant.
It’s an environmental condition and it can happen to any variety of tomato although some tomatoes are more prone to struggle with the disease.
However, it’s not isolated to tomatoes. Blossom end rot can also affect peppers, eggplant, squash, and watermelon.
What causes blossom end rot on tomatoes?
Blossom end rot is a disorder of growing fruit that causes the cells at the blossom end of the fruit to die. The cellular death seems to be due to a lack of calcium within the affected cells.
The exact cause of the calcium deficiency in the affected cells is largely debated, but we do know that the disorder only affects rapidly growing fruit. Size of the fruit matters as well because cherry tomatoes are not affected by the problem.
Blossom end rot occurs during periods of rapid growth and can be induced by:
- low calcium
- low phosphorous
- high magnesium
- high nitrogen
- high potassium
- high salinity
- waterlogged roots
- low humidity
- too much light and heat on the growing fruit
It’s extremely disappointing, but also very common to lose tomatoes to blossom end rot. And if it’s happening to you, don’t worry. You didn’t do anything wrong.
Options for blossom end rot treatment
At the point you see blossom end rot on a tomato, there is nothing to do for that particular fruit. But you may be wondering if you need to treat the entire plant to prevent further tomatoes being affected by blossom end rot.
Certain stressful conditions can lead to blossom end rot, so make sure your tomato plants aren’t stressed by drought & check the pH of your soil. Ideal soil pH for tomatoes is 6.5.
If it’s over 7 or under 6, your plants will have a hard time taking up nutrients from the soil. Adding lime will raise the pH. Adding sulfur products will lower it.
Options for blossom end rot prevention
There are a lot of tips and suggestions for preventing blossom end rot on the web. Some of them are based in truth, and some are right out myths.
Blossom end rot is a complex process that is influenced by lots of environmental factors. So what has seemed to work for some gardeners will not necessarily work for other gardeners.
Some commonly recommended blossom end rot treatments include:
Heavily mulching with nutrient rich compost and/or applying a calcium fertilizer
Some say that heavy mulching will protect your plants from the water stress which may lead to blossom end rot. It is true that blossom end rot can be caused by water stress, so preventing that with whatever means you choose can help.
However, unless you’ve had a soil test to confirm that your soil is deficient in calcium (which is usually not the case), adding calcium to the soil will not help prevent or treat blossom end rot.
In fact, some suggest that the addition of a lot of nutrients might encourage rapid growth which may lead to blossom end rot.
Planting tomatoes with Epsom salts and crushed eggshells
Epsom salts contain magnesium and sulfur. These are important nutrients for plants, so if your soil is deficient in magnesium and sulfur, then it will help your plants.
High magnesium can compete with calcium uptake in tomato roots. So too much Epsom salt can make blossom end rot on your tomatoes more likely, so be careful not to overdo it.
Eggshells do contain calcium, but the calcium from the eggshells will not immediately be available for uptake by the plants. They’ll take several months to be decomposed into the soil and become available to your tomatoes.
Adding eggs and eggshells can improve the health of your soil over time but it’s not an effective way to treat blossom end rot on your tomato plants.
Adding lime or dolomite lime to the soil
It is true that lime can improve the quality of your soil. It adds calcium and dolomite lime contains magnesium.
If your soil is acidic (pH is too low), the lime will also help neutralize the pH into a comfortable range for your plants. The ideal soil pH varies between plants but most vegetables are comfy at about 6.5.
However, you should always check the pH of your soil before adding lime. If you get your soil pH too high, it can be hard to grow anything. It’s super easy to find out the pH of your soil with a soil pH kit.
Here is some more information about testing the pH in your garden.
Blossom end rot spray
There is insufficient evidence to support that tomatoes can absorb calcium through the fruit or will transport calcium supplementation from the leaves to the fruit.
The problem is usually not a lack of available calcium anyway. The problem is that the plant is sending available calcium to other parts of the plant.
A better way to address blossom end rot is to make sure that you are watering regularly, but not over-watering, and fertilizing appropriately, but not over fertilizing.
The good news is that blossom end rot will usually go away on its own. Yay!
This seems to be a condition that most plants will grow out of. So whether you try one of the blossom end rot treatments or not, your plants will likely recover with the next round of fruit.
There are some types of tomatoes that are more prone to blossom end rot. We’ve certainly experienced years where we lost most of the tomatoes on some plants due to blossom end rot.
Paste type tomatoes do seem to be more prone to this problem while it is less common in cherry tomatoes.
If you find that your veggie patch is plagued by blossom end rot this year, the first thing to do is check your watering schedule and get a soil test to make sure that your soil is within the appropriate pH range.
The next thing to do is pull off those mushy fruits and toss them into the compost. And take heart…
You didn’t do anything wrong, and there’s nothing you can do to fix it.
You can, however, avoid the problem by planting a more resistant variety. Cherry and heart-shaped tomatoes are less likely to be afflicted by blossom end rot.
And make sure you’re taking notes in your garden journal so you can avoid varieties that don’t perform well for you.
I’d love to hear your thoughts on this subject. Please leave me a comment below.