When the temperature rises above 90° and the humidity is high, cool-season forages suffer, warns Bruce Anderson, University of Nebraska Extension forage specialist.
Alfalfa and clovers, bromegrass, orchardgrass, fescues and wheatgrasses grow slowly in hot weather, their quality drops and they recover slowly after cutting or grazing, says Anderson.
“Warm-season grasses are just the opposite,” he says. “Millet, sudangrass, sorghums and our native bluestems, gramas, switchgrass and other warm-season grasses thrive when the temperature is around 90°. Their metabolism runs at peak efficiency when it is hot, so they grow rapidly while maintaining reasonable forage quality and good root growth.”
That assumes that they have adequate moisture, he adds. Once they dry up, those grasses will overheat just as cool-season grasses do at lower temperatures.
“As you graze or hay, be aware of the stress weather is putting on your forage,” Anderson advises. “When it’s too hot, be prepared to allow plants to recover for a longer time before next use, and don’t expect high feed values.”