ABSTRACT
Summary Stand establishment in northern latitudes presents a challenging problem that must be conscientiously dealt with to obtain optimum response from introduced grasses. Many variables have been studied in regard to establishment, but relatively little research has been done on early seedling growth and development per se. Yet early in growth is when plants are most vulnerable 561to winter injury, dessication, competition, grazing, and other adverse impacts. Our research has sought to identify some of the critical morphological features in seedlings that can influence grass establishment. Specifically, objectives were (1) to define and quantify relationships between morphological development and winter injury, survival, and growth, and (2) to develop a management strategy for stand establishment that considers early seedling growth and development. Three perennial forage species—crested wheatgrass (Agropyron desertorum [Fisch.] Schult.), pubescent wheatgrass (Agropyron intermedium subsp. trichophorum [Link] Reichb. ex Hegi), and Russian wildrye (Elymus junceus Fisch.)—were seeded in late summer and early fall to obtain seedlings with diverse morphological characteristics. Individual seedlings that emerged were marked after reaching a winter-dormant condition or upon emerging the following spring. The number of leaves was counted and correlated with winter damage, spring and fall growth, and summer mortality. Winter injury was inversely related to plant size in all three species and could best be expressed by a quadratic curve. As plant size increased, winter damage decreased. Spring and fall growth were directly related to both seedling size and winter injury. Greater growth and higher summer survival were found in seedlings that had more leaves in the early spring, while substantially less growth and survival were observed in plants that emerged in the spring from late autumn seeding. Growth relationships were readily quantified by an exponential curve. With respect to management applications, it is highly desirable to minimize the grazing deferment interval so that forage utilization can begin sooner. Our results show that minimization is best accomplished by late-summer planting to assure that seedlings have three or more leaves before winter. Such seedling development results in reduced winter injury, better summer survival, and greater growth during the following season.
