The gentleman was polite on the phone but clearly frustrated. His six-foot high tomatoes in barrels at a seven Ph were flowering but then the flowers were falling off. He said something similar had happened to his potatoes last year.
Now tomatoes are very close to my heart. I even wrote a speech in high school about tomatoes’ first name, “love apples.” They are actually fruits re-categorized as vegetables to work around a 19th Century import tax.
There are several factors that cause tomatoes to drop their flowers, starting with the impact of record high temperatures. Tomatoes, like most flowering plants, go into survival mode if temperatures are above 90 F for five or more days in a row. We just set record temperatures for June in Missouri so the record hot temperatures may be a leading culprit.
Plant survival mode means most systems are shut down, including pollen production. It’s why a plant may seem to die in hot weather and yet reappear the following year. As long as the roots can pull through, most plants will survive.
Tied to temperature is high humidity. Humidity that is too high prevents pollen from sticking to the stigma once it is released. Without pollen, there are no pollinators and without pollinators, there are no flowers that produce tomatoes.
Leading tomato pollinators are native bees, especially bumble bees. These little hoodlums of the bee world literally shake the plant, releasing pollen all over the stigma and themselves. When high temperatures shut down pollen production, they also put bees out of business.
In addition to weather conditions, these tomato plants may be getting too much nitrogen fertilizer. Nitrogen encourages the green growth that has spurred these plants to six feet. A balanced plant meal requires nitrogen for growth, phosphorous for moving energy through the plant and potassium for stress tolerance. Our Ozark soil can provide nitrogen but the other two fertilizer elements usually need a boost. Soil testing through a local University of Missouri Extension office will help determine what is missing. A test costs $14 and includes not only what is in your soil but what you need to do to amend it.
The other delicate part of raising tomatoes is watering. Tomato roots in open ground can grow to five feet deep. If you have a garden area that deep in the Ozarks, I would love to see it. Sorry, I digress. Tomatoes even grown in containers prefer to be evenly moist so with temperatures, and humidity, either at record levels or varying widely requires careful monitoring. I have sunken plastic bottles with holes in pots keeping my tomatoes company so that I can better keep the roots moist. I use a paint stick propped into the side and moved over an inch to check how wet the soil is before I water.
And that speech about tomatoes I gave in high school? I got an A. I suspect it would have been an A+ if I had not eaten the display.
Charlotte Ekker Wiggins is a certified gardener and beekeeper. Copyright 2016 used with permission, all rights reserved. This material may not be published, broadcast, rewritten or redistributed. Contact Charlotte at firstname.lastname@example.org.
NATURE KNOWS BEST – Another reason tomatoes may drop flowers is too many fruits on one stem. Once weather cooperates and tomatoes are picked, blossom drop should stop. (Photos by Charlotte Ekker Wiggins).
SURVIVAL MODE – Record hot temperatures over 90F for several days in a row cause plants like tomatoes to drop flowers. Blossom drop is one of several ways plants survive unfavorable weather conditions.