Cold resistance of various legumes and grasses in early stages of growth

The survival at low temperatures of five grasses and five legumes at different stages of seedling development was studied under artificial growing, hardening, and freezing conditions. All the grasses except brome showed a noticeable reduction in survival from freezing at -10 degrees C for 8 hours when the seeds had germinated but not emerged from the soil. Conversely, the legumes showed relatively better survival than the grasses at this early stage. When the grasses had been grown in the greenhouse for 1 week, at which time they were in the one-leaf stage, preceding hardening and freezing the survival was relatively good. Then again after 3 weeks of greenhouse growth the survival of all grasses declined, with the exception of meadow fescue. Of the grasses, reed canary showed the poorest survival during early stages of growth, particularly the stages represented by 2, 3, and 4 weeks of greenhouse growth. At 5 weeks or more of greenhouse growth all grasses showed relatively good survival. The legumes showed less than 20% survival for three stages represented by 1, 2, and 3 weeks of greenhouse growth. Alfalfa was the first legume to show increased survival, which was at the stage represented by 4 weeks of growth. Alsike clover, red clover, and white clover began to show improved survival at 5 weeks of growth. Sweet clover survival was almost nil until the stage represented by 9 weeks of greenhouse growth. The results from this study show that, although timothy, Kentucky blue, and brome tend to show some weakness in survival to freezing when the second leaf is developing, the survival is sufficiently high to indicate that they could be seeded rather late in the fall. Also meadow fescue which showed good survival at this stage could be seeded late in the fall. Reed canary grass, however showed low survival from freezing while in the early stages of development, indicating that it should be seeded early in the fall or so late that no germination occurs before winter. The study further emphasizes the point that fall seedings of legumes in Minnesota are not practical unless seeding is made so late that no, or very little, germination occurs before winter. Field tests at St. Paul show that seedings of alfalfa made later than August 1 to 10 are commonly winterkilled.