Optimal fine fescue mixture seeding dates in the northern United States

Research is lacking on best establishment practices of fine fescues (Festuca spp.), such as optimal seeding timings, which are well known for other cool-season turfgrasses. Our objective was to document establishment and determine optimal seeding timings for mixed stand of fine fescue in multiple cool-season climate zones in the United States. From 2019 to 2020, an experiment was replicated across four locations in the northern United States to investigate nine monthly fine fescue mixture seeding timings from March through November. Fine fescue seedling emergence typically hastened as temperatures increased during the growing season, and emergence required 6.1–9.4 d when soil temperatures were within a range of 15–25 °C. Final grid count data across multiple sites indicated that seeding fine fescues in August, September, and at times, July, will likely produce the best establishment with the lowest weed infestation pressure, and there may be more flexibility in seeding timings in a Mediterranean climate, such as Oregon. Seeding fine fescues in the early-spring or late-autumn can be more unreliable because of greater likelihood of weed infestation, suboptimal growing conditions, and potential of a late-autumn seeding to act as an unintended dormant seeding. Results indicate the weed invasion pressure of specific weeds will vary depending life cycle of weed and seeding time of year. Overall, seeding a fine fescue mixture in August or September will increase likelihood of success in cool-season climate zones in the United States with a wider seeding window when planting in Mediterranean climates.