Germinability of annual bluegrass seed in western Oregon grass seed production systems

Plain Language Summary Annual bluegrass ( Poa annua L.) is a problematic weed in grass seed production fields because it germinates over a long period. It is difficult to selectively control, and its presence incurs increased seed cleaning costs. Research in eastern USA suggests variability across regions when using environmental‐based models to predict annual bluegrass seed germinability. Data from western USA grass seed production is lacking; therefore, researchers collected annual bluegrass seed in Corvallis, Oregon every 50 growing degree days (GDD 0C ; base 0°C) over three years and subjected them to germination testing. Seeds collected prior to 300 GDD were less likely to germinate compared to subsequent timings, except when 12 of 14 seeds germinated at 50 GDD 0C in 2025. Findings suggest that a GDD based annual bluegrass seed germinability model may be beneficial in this system. Germination occurred up to 28 days, suggesting that the standard 21‐day test may be inadequate to fully quantify germinability.