In the southeast U.S., perennial grasses such as tall fescue, bermudagrass and bahiagrass make up a large portion of our annual hay crop. As temperatures begin to drop and the days become shorter, warm-season perennials, like bermudagrass and bahiagrass, begin to go into a winter dormancy period.
As this shift occurs in the fall and we see reduced forage growth aboveground, let’s also think some about what is occurring below the ground. Perennial forages have an extensive root system which holds reserves that encourage plant regrowth. At the end of the growing season, warm-season perennial grasses work overtime to store carbohydrates. These carbs are used to help boost plant emergence in the spring when weather conditions begin to moderate. Many producers aim to take one last hay cutting from their warm-season fields in the late fall.
Time of the last cutting for the season is key to not deplete root reserves. When perennial forages are cut late in the season just a couple of weeks before a killing frost, this can hurt stand health. One reason is because if hay is cut two weeks prior to a frost, the stand will try to actively regrow during this time period. This requires plants to pull from their root reserves that would otherwise be stored for spring. If a frost hits during this time of growth, there is no chance for the stand to recover needed root reserves.
In some instances, it's best to describe the last hay cutting as an “all-or-nothing” approach. The “all” approach is to time the last hay cutting right around the time of dormancy-inducing frost. If hay can be cut right before or even just shortly after the frost, this timeframe works because plants will not try to actively regrow during this time.
The “nothing” strategy is that timing of the last cutting should generally be at least 30 days prior to a killing frost in warm-season forages. This allows for adequate growth for harvest and for forages to be out of their rapid growth stage. Following the killing frost, remaining forage can be mowed or grazed. If fields appear to have weakened over time, it is better to follow the nothing strategy, which allows forages to build up some of their root reserves for the spring. The less reserves for regrowth, the more other undesirable species can compete and begin to fill in a stand.
