It’s disappointing to see a tomato in mid-growth with a bruised-looking splotch on the blossom part of the fruit. Blossom end rot in tomatoes (BER) is a common problem for gardeners. Its cause lies in a plant’s inability to absorb enough calcium to reach the fruit.
Read on if you’re seeing tomatoes rotting on the bottom to learn how to stop tomato blossom end rot.
Tomato Plants with Blossom Rot
The spot on the fruit where the blossom once was marks the center of blossom end rot. Typically, the problem starts on the first flush of fruits and those that haven’t quite reached their full size. The spot appears watery and yellowish-brown at first and will grow until it destroys much of the fruit. Other vegetables like bell peppers, eggplant, and squash can be subject to blossom rot as well.
What blossom end rot is telling you is that the fruit is not receiving enough calcium, even though there may be ample calcium in the soil and the plant’s leaves.
What Causes Blossom End Rot in Tomatoes?
It’s all about the roots and their ability to carry calcium upward. There are several things that will prevent a tomato plant’s roots from uploading calcium to the plant’s fruit. Calcium is transported up from the roots to the fruit by water, so if you’ve had a dry spell or haven’t sufficiently or consistently watered your plants, you may see blossom rot.
If you’ve given your new plants too much fertilizer, they may be growing too quickly, which can prevent the roots from delivering enough calcium fast enough to keep up with the growth. If your plant’s roots are crowded or waterlogged, they may not be able to draw calcium up to the fruit.
Finally, although not as common, your soil may be lacking in calcium. You should do a soil test first and, if this is the problem, adding a bit of lime should help.
How to Stop Tomato Blossom Rot
Try to wait until your soil warms up to 70 degrees F. (21 C.) before planting new tomatoes.
Don’t fluctuate with watering. As your tomatoes grow, make sure they’re getting a full inch (2.5 cm.) of water each week, whether it’s from irrigation or rainfall. If you water too much, your roots may rot and give you the same negative results. Likewise, if the tomato roots get dry or crowded by others, they won’t do their job of carrying up sufficient calcium.
Consistent watering is key. Remember to never ever water from above, but always water tomatoes at ground level. You may want to place some organic mulch around the plants to retain moisture.
Tomato end blossom rot will usually affect the first round or two of fruits. Although blossom end rot can leave the plant vulnerable to disease, it is not a contagious condition and won’t travel among the fruits, so unless you find you have a severe calcium deficiency, there’s no need for sprays or fungicides. Removing the affected fruit and continuing with a consistent watering schedule may clear the problem for the fruits that follow.
If you do find your soil is truly lacking in calcium, you can add a bit of lime or gypsum to the soil or use a foliar spray to help the leaves take up calcium. If you have an otherwise lovely tomato that’s rotten on the bottom, cut the rotted part away and eat the rest.
Looking for additional tips on growing perfect tomatoes? Download our FREE Tomato Growing Guide and learn how to grow delicious tomatoes.