By Molly Biggs, Adam Thoms, and S. Fei, Iowa State University
Dry cold winters in the Midwest and Great Plains can be challenging for survival of creeping bentgrass putting greens. During winters with little snow, turfgrass surfaces are left exposed to the drying winter winds. In these situations, golf course superintendents will apply a variety of techniques to try to increase the putting green’s chances of survival. These techniques include covering the surface with breathable covers, sand topdressing, spraying anti-transpirant (a coating that stops the loss of moisture from the plant) products, and various soil surfactants (to increase water holding in the root zone). However, there is limited data on how these practices help with winter survival of creeping bentgrass putting greens.
Previous research has looked at how turfgrass cell size can be used as a prediction for how various cultivars of tall fescue and Kentucky bluegrass will handle traffic. The larger the space between cells (intercellular void space) the more traffic tolerant the turfgrass cultivar. There is also research that indicates that smaller cells with less water will handle freezing better than larger cells in other plants. We tested creeping bentgrass treated with various soil surfactants, an anti-transpirant, a combination of a soil surfactant and an anti-transpirant, along with an untreated control (Figure 1) to measure cell size with cryo-scanning electron microscope imaging (Figure 2).
The treated creeping bentgrass underwent an unirrigated six-week cold period designed to simulate winter desiccation. The plants lost green cover during the cold period. After the six-week period, the plants were moved to a greenhouse to look at recovery. Recovery, determined by percent green cover, was measured daily for three weeks following the cold period to quantify turfgrass winter survival.
Cell size area differed significantly among treatments, with two of the soil surfactants producing the largest cells and the untreated control producing the smallest. Recovery percent green cover varied between study runs; however, in study run 2, the untreated creeping bentgrass exhibited the greatest spring green-up, while treatments associated with larger pre-winter cell size showed reduced recovery. These observations suggest a potential inverse relationship between cell size entering dormancy and subsequent spring performance following desiccation stress. Under these simulated conditions, spray-applied treatments did not improve post-winter recovery compared to the untreated control. These findings align with previous research showing that physical protection strategies, like sand topdressing and turf covers, may better maintain crown hydration and reduce the likelihood of winter desiccation injury than chemical treatments alone.