Ew! Why Is the Bottom of My Tomato Rotten?

If the tomato is still on the vine and the bottom is black or brown and looks rotten,  it is likely a condition called blossom-end rot. Blossom-end rot is  a calcium deficiency in the plant.  This condition can affect tomatoes but it can also affect peppers, squash, eggplant, cucumber, and melons. Look for the tell-tale signs of black or brown rotten spots on the fruit or vegetable.  If you are experiencing this in your garden, don’t worry, you aren’t alone.  Most gardeners have had to deal with this issue at some point in time.

(Note. Affected fruits and vegetables should be not be consumed and should be discarded.)

What Causes Blossom-end rot?

Blossom-end rot is a condition in which there is a lack of calcium in the plant.  There are several possible causes for this issue to develop including the following:

  1.  The soil lacks calcium.
  2. The calcium in the soil  is plentiful but is chemically bound up and unavailable to your plant.
  3. Too much fertilizer, especially nitrogen derived from ammonia.
  4. Inconsistent moisture levels.

 What is the solution to Blossom-end rot?

Soil PH.  First check the soil ph. If the ph of the soil is wrong, adding more calcium to the soil won’t help.  Testing kits  that check soil ph can be purchased at most garden stores or online for under $10.00.  Follow the directions on the package to test your soil.  Ideally your soil should have a ph of 6.5 to 6.8.  If the ph is not within this range, certain nutrients, like calcium,  will be chemically bound up and unavailable for absorption. If your test shows a ph higher than 6.8, then your soil is alkaline and you will need to add sulfur to lower the ph.  If the ph is lower than 6.5, then you have acidic soil and you will need to add lime to raise the ph. Lime has the added benefit in that it actually contains calcium that your plants can use.

Lack of Calcium.  Second, if you tested the soil and the soil ph is not the problem, then the problem may be a lack of calcium in the soil. Even though as previously stated, lime contains calcium, if the soil ph is within the 6.5 to 6.8 range, then adding lime will throw off the ph.  In this case, add gypsum.  Gypsum adds calcium and it will not change the soil ph, however, it will add salt so follow the directions on the package.  Too much salt in the soil adds a whole new set of problems to the garden that you don’t want.

For a longer term solution to calcium deficiency in your soil, add bone meal or egg shells to the garden.  Both bone meal and eggs shells are comprised of calcium.  These organic forms of calcium need time to break down into a source that is usable by plants so it may take a year or more before results can be seen.

Fertilizer.  Third, the problem may lie with your fertilizer. Fertilizers with a lot of nitrogen, especially nitrogen derived from ammonia, cause the plant to grow too fast and the plant is not able to absorb enough calcium to keep up with its growth rate.  I always suggest organic fertilizers and compost.  These fertilizers come from natural sources and add nutrients and trace minerals slowly  and in amounts that your plants need for proper growth. Synthetic slow release fertilizers are also a good option as they are easy to apply and they slowly release the nutrients your plants need over the course of the growing season. Synthetic liquid fertilizers must be applied again and again over the growing season, they tend to add salt to the soil, and they also promote unnatural growth in plants so I don’t usually recommend them for in-ground gardens. (Container plants are the exception for synthetic liquid fertilizers.)

Watering.  Finally, make sure that you are keeping your garden consistently moist.  Alternating between wet conditions and then extreme dry conditions may interfere with your plant’s ability to absorb calcium.  This is especially true in potted plants. To keep your garden consistently moist it is important to water your garden adequately, regularly, and in the proper amounts.  Watering will depend on the weather and your soil.  Heavy clay soil tends to hold moisture and sandy soil tends to dry out too quickly by wicking water away. Both types of soils should be amended with generous amounts of compost to add organic matter, improve soil quality, and help maintain moisture levels for healthy vital garden plants.

To keep soil consistently moist, soaker hose works best and is easy to use.  Soaker hose is usually black in color and it’s porous.  The water in the hose slowly drips from the entire length of the hose.  Lay the soaker hose along the length of your plant row and turn the water on for about 20 minutes to slowly water your plants.   This time may need to be adjusted depending on your soil structure.  The ground should be wet several inches down but don’t allow standing water to form that doesn’t soak in within a short period of time.  That means there is too much water. Check the soil every few days.  If the soil looks dry on top and it’s dry if you stick your finger in the ground about 2 inches, then water again.

Sprinklers are commonly used to water gardens.  Sprinklers provide adequate water but they can cause problems with disease, especially fungal issues. If you use a sprinkler, always water your garden in the morning. This allows the plants to dry fully before the afternoon sun hits. Watering your garden in the hot afternoon sun  can cause burns (called sun scald) on your plants. Watering at night is also not recommended as it allows water to sit on the plants for a length of time which encourages disease and rot. Watering in the morning is best and can be made more convenient by the use of timers that can be purchased at garden stores or online.

Blossom-end rot is a condition that is easily controlled if you know why it happens and the step to take to cure it.  Every gardener will deal with this issue at some time.  If it happens to you, throw out the infected fruit, go through the steps to check the cause and apply the appropriate remedy.  In no time at all, you’ll have beautiful tomatoes growing in your garden ready to pick for that amazing evening dish!

Happy Gardening!

 

Quote of the Day

“Knowledge is knowing that a tomato is a fruit.  Wisdom is knowing not to put it in a fruit salad.”  – Brian O’Driscoll

 

 

 

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