Seed coating treatments alter emergence windows of native Intermountain West U.S. grasses under different regimes of water availability

Abstract

Introduction Seed-based restoration is widely implemented to recover degraded lands but often fails. Seed enhancement technologies may improve outcomes by shifting emergence to target favorable climate windows and serving as a bet-hedging strategy against increasingly variable precipitation patterns. Objectives To test the potential benefit of these technologies, we applied seed coatings designed to accelerate or delay emergence to four native Intermountain West perennial grasses that are commonly used for restoration. Methods We subjected seeds to six different watering regimes in the greenhouse that represented variation in precipitation timing and amount and compared the emergence, growth, and biomass of coated and uncoated seedlings. Results Seed coating designed to accelerate germination strongly increased emergence in species with high dormancy requirements, while seed coating designed to delay germination decreased emergence in species with low dormancy by about half and postponed emergence by up to 15 days. These coatings altered emergence timing regardless of watering regime, suggesting that seed coating could expand emergence windows under variable precipitation regimes. Seedling growth and total biomass were less dependent on seed coating and were more driven by the average amount of soil moisture provisioned to the developing plant. While seed coating designed to accelerate germination increased the emergence of two grass species, growth decreased during late periods of water availability, suggesting a trade-off in seedling performance. Conclusions Our results show promise for seed coatings to shift windows of emergence, but further field testing could improve our understanding of their effects in restoration settings.