Last year I had something weird happen to my tomatoes - the end of some of them turned brown and looked rotten. Tomatoes that were produced after that didn’t seem to have that problem. What the heck was going on? KW

Tomatoes are like a lot of us, unless the conditions are just right, they’re not going to do what they are supposed to do. But sometimes these problems are not caused by a disease or a pest but by some environmental condition.

The problem you are describing was likely Blossom-End Rot. You’ll know you have an issue with blossom-end rot when the blossom end of your tomato starts turning brown. As this brown area starts to expand, the brown part can start to feel kind of leathery. When this happens, the fruit becomes more susceptible to disease.

Blossom-end rot can be caused by several things, high temperatures, wind, drought, but most likely inconsistency in water availability. You’ll likely detect blossom-end rot on your tomatoes after a period of a lot of rain. Excessive rain or excessive watering soaks the soil for an extended period of time which limits the plant’s ability to uptake calcium which causes the brown part of the fruit. While it might seem logical to add calcium when there is a calcium deficiency, adding calcium to the soil will not improve the situation. You can read a lot of suggestions on how to combat blossom-end rot on various online resources, however, the condition tends to work itself out when the situation with too much water improves and it is able to pull up the necessary calcium.

Another potential environmental issue with tomatoes is blossom drop. Blossom drop tends to occur as summer heats up. We can see blossom drop on our tomatoes when daytime temperatures rise above 90 degrees. This heat can inhibit pollination, so the un-pollinated flowers just drop off.

Cooler temperatures can also contribute to blossom drop if it gets cooler than 55 degrees during the night. There’s nothing wrong with the plant, it’s just picky about when pollination can occur.

Because of this, a lot of our tomato plants tend to slow down or stop production during the height of summer, but if we can keep them alive, they’ll start to produce again in the fall. To overcome this challenge, some people just plant a second round of tomatoes in their fall garden.

Catface is another environmental problem found in tomatoes. Catfacing happens when two conditions coincide; temperatures are below 58 degrees, and the tomato plant is flowering. During the colder temperature, the flower doesn’t develop properly so when it is fertilized, there can be some imperfections in the fruit. An herbicide called 2,4-D which is used commonly on broad-leaf weeds can also be a contributor as 2,4-D tends to vaporize and drift. This drifting can cause a malformation in the flower leading to catfacing. Larger varieties of tomatoes tend to have more problems with catfacing that some of the others.

Once we learn about all the potential issues that can work against the harvest in our gardens, it can be amazing we get any fruit at all…but we do. Good luck!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701 or by emailing us at mg@tulsamastergardeners.org. Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org