Evaluation of Candidate Roadside Turfgrasses for Heat Stress Tolerance.

Roadsides are harsh environments subjected to ice, salt and heat stresses. However these small bands of vegetation are extremely important for the prevention of soil erosion along roadways. Previous research on turfgrass heat stress tolerance has been limited to a small number of species or cultivars. Our program is identifying the best candidates for use on roadsides in Minnesota and similar climates. Therefore, we assessed heat stress tolerance of 35 turfgrasses, representing 14 species. Eight replications of each entry were established for 12 weeks in the greenhouse. Half of the replicates were acclimated for 2 weeks in a growth chamber before being subjected to 49 days of heat stress (35°C/25°C day/night) followed by a 4 week recovery period (25°C/15°C day/night). The second half of the replicates were grown at non-stress conditions throughout the experiment. Each week, Normalized Difference Vegetative Index and digital images were taken to estimate the percentage of green tissue. Additionally, membrane stability (electrolyte leakage), and soil temperature were recorded for a single entry of each species. In some species, cultivars and selections differed in heat stress response. For example, ‘Nanook’ hard fescue was extremely sensitive to heat stress whereas ‘Gladiator’ hard fescue performed well. Buffalograss (the only warm-season grass in our study), Kentucky bluegrass and slender creeping red fescue were all tolerant of the heat stress. Canada bluegrass, blue grama and smooth brome were all tolerant of heat stress, but only one cultivar was tested for each species, making species-wide generalizations difficult. Almost all entries were able to recover from the heat stress during the recovery period except for Nanook hard fescue and ‘Quatro’ sheep fescue. Altogether, we were able to identify turfgrass cultivars and selections that should be able to perform adequately in high temperature urban environments.