Here are some of the tomato questions I’ve received over the past few weeks. I believe these are recurring problems in some gardens this year.

Why aren’t my tomatoes ripening? The ripening process of a tomato will slow down significantly when the temperatures reach above 90 degrees. Optimum temperatures for ripening of a tomato are around 70-75 degrees. Do not panic though, the fruit will ripen when it is ready to ripen.  

It is all based upon the chemicals that make the tomato turn red, the main two being lycopene and carotene. These are the two responsible for making tomatoes turn red. These two chemicals will almost completely stop being produced when the temperatures are hot.  

Just be patient is my only advice for this. To make you feel better, I have plenty of green fruit and I have yet to pick a large red tomato.

Why is the bottom of my tomato turning black and looking rotten? This question is very common each year with the fluctuations of temperatures and rainfall. The simple answer is blossom end rot, but it has a complicated answer.  

Blossom end rot is caused by a deficiency in calcium in the developing fruit. Most Tennessee soils have enough calcium in them so the main cause of blossom end rot is the plant not being able to take up the calcium when it needed it most. This goes back to making sure the tomatoes are watered appropriately when fruit is developing. Most growing vegetables need only about 1.5 inches of water per week.  

Why are the leaves of my tomatoes curling? Curling leaves on a tomato could mean two culprits: physiological leaf curl or herbicide residue in the soil or the amendments added to the soil such as manure.  

Physiological leaf curl is caused by the transitions of weather. Changes in temperature, rainfall and even humidity will cause the leaves to curl, but this will not affect the fruit at all.  

Herbicide residue is another issue though. Some herbicides that are used on hay will pass through the animal and will remain in the manure for a couple of years. These manures cannot be used on the garden because the plant will slowly succumb to the herbicide residue.

Lucas Holman is the Horticulture UT-TSU Extension Agent for Wilson County. He can be reached at (615) 444-9584 or Lholman1@utk.edu.


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