An Uphill Climb for Bermudagrass
For many turfgrass managers, the arrival of Memorial Day officially closes the book on spring and marks the start of summer. It’s been a rather tumultuous spring for bermudagrass in East Tennessee with plants behind normal benchmarks for growth and vigor. A look back at spring weather patterns highlights several factors that have negatively affected bermudagrass performance in 2021.
A Historically Late Final Frost
Low temperature at the University of Tennessee East Tennessee AgResearch & Education Center — Plant Sciences Unit (home of @UTturfgrass research) measured 33F on April 22nd. While above freezing, this sharp drop in temperature resulted in significant frost across many areas of East Tennessee. For bermudagrass, this historically late final frost event was highly detrimental; spring green-up was halted and some stands were sent back into dormancy, essentially forced to restart the greening process with stored carbohydrates already reduced. Comparatively, final frost events in Knoxville occurred on April 11, 2020 and April 1, 2019.
A Lack of Overall Warmth
Every turfgrass manager is well aware that warm-season species like bermudagrass require heat in order to grow optimally. Heat accumulation is quantified in units of growing degree days (GDD). Typically, GDDs are calculated each day and a running total is kept from January 1 through the end of the season. A comparison of GDD accumulation for Knoxville, TN is presented in Figure 1. Simply put, heat accumulation in 2021 has lagged behind the previous two seasons for the months of March, April, and May. Bermudagrass stands negatively affected by a historically late final frost have been tasked with recovering in conditions that are far from ideal for optimal growth.
A Lack of Rainfall
The saying “April showers bring May flowers” has not rung true in 2021. April and May rainfall accumulation in Knoxville lagged behind 2020 totals (Figure 2). During the eight weeks of April and May, the East Tennessee AgResearch & Education Center — Plant Sciences Unit only received three rainfall events >0.3" with no measurable rainfall detected on many days.
A Perfect Storm
Mother Nature has put together a perfect storm for slow bermudagrass growth this spring. The late frost hampered bermudagrass green-up, with plants tasked to recover under climactic conditions not favorable for bermudagrass growth — cool temperatures and drought. Fingers crossed the arrival of summer will bring favorable conditions to remedy this slow start to 2021.
