Heat and drought are two major abiotic stresses which cause turf quality to decline greatly. Tall fescue (Lolium arundinacea) has widely been used as a utility turf in low input applications for decades; however, recent advances in the breeding have allowed tall fescue to be used in many other situations.  Tall fescue is no longer the large, coarse textured, purely bunch type grass that it used to be. New lower growing genotypes with a more lateral growth habit are making tall fescue a viable choice for home lawns and other areas of moderate cultural intensity. Tall fescue has been shown to be more tolerant to summer stress than other turfgrass species such as Kentucky bluegrass, however, little research has been done to characterize this tolerance.  Summer stress consists of both heat and drought stress.  Understanding which of these factors is stressing a particular turf is important in management strategies as well as future breeding programs.  This study was designed to determine whether heat or drought was the predominate cause of stress in different tall fescue clones.

Twenty-four tall fescue clones were selected based on field performance as spaced plants; twelve that were perceived to be tolerant and twelve that were perceived to be susceptible to summer stress.  These twenty-four clones were subjected to heat and drought stress in combination and alone by placing them in growth chambers and controlling their temperature and water supply.  A number of physiological measurements were taken including turf quality, relative water content, electrolyte leakage, and photochemical efficiency. Overall, the effects of drought resulted in the most stressful conditions while, as a whole, clones being stressed by heat alone appeared to maintain their overall quality for a longer period. In addition, different clones were found to perform better when exposed to different stresses.