If you look forward to perfect peppers, but are disappointed when they get sunburned, there aren’t as many, or they aren’t as big, chances are that sunlight is to blame. Solar intensity and high temperatures work against getting the most out of pepper crops.
However, research on shading the peppers is casting light on the benefits of cooling things off for the leaves and in the root zone. Heat stress reduces the plant’s ability to photosynthesize and cool itself efficiently, in turn, limiting root development. Increasingly higher temperatures during the summer months often limits root growth and damages fruit.
Colorado’s research into finding solutions to this problem is one led by Mike Bartolo, senior research scientist and manager of the Arkansas Valley Research Center in Rocky Ford. He’s been researching the development of chili peppers since 1992.
Bartolo’s research into preventing sunscald on the peppers’ fruit led him to using a 30 percent shade barrier over some of the plants to protect the fruit from harmful rays. And since that shade is proving effective in also shielding plants from high temperatures, the transplants that he covered with shade in early June aren’t showing the stress that the exposed peppers are.
Globally, researchers concerned with the climate change effects on crop production are exploring ways to buffer hotter temperatures. Growing under shade cloth has garnered interest, and researchers are working to find the type of shade cloth that gives the most benefit. Researchers at the University of Georgia found that the color of the shade netting doesn’t make much difference — however, leaf surface temperature remained higher while under white shade cloth.
“In our gardens, peppers covered with shade cloth or floating row covers are also in much better shape,” Bartolo said. “Popping a tent of 30-percent cloth over your crop might help get things growing again. As long as the stem is OK and not injured by sunscald, things should get moving again once things cool down or you shade the plant.”
A bit of shade is helpful to other plants, as well, such as basil or tomatoes during fruit production. Mulching also helps keep the plant cool since it protects roots from water loss and soil cracking.
Shade cloth is available at garden centers in various lengths. It’s a durable fabric that can be used for several years. When covering plants, remember that this is to be suspended above them, unlike floating row covers that can sit right on the plants. Create a frame for holding the shade barrier 2-4 feet above the plants, taking care that it’s secure for wind.
Floating row covers provide about 15-19 percent shade, which might not be enough at this time to break the grip of heat. Early in the season it would help for root development, so keep it handy for next year.