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

Authors: Mattox, Clint; Dibblee, Sebastian

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2025
Publication Date: 4/24/2026
Citation: Mattox, C.M., Dibblee, S.D. 2026. Germinability of annual bluegrass seed in western Oregon grass seed production systems. Crop, Forage & Turfgrass Management. 12(1). Article e70109. https://doi.org/10.1002/cft2.70109.
DOI: https://doi.org/10.1002/cft2.70109

Interpretive Summary: Annual bluegrass is a problematic weed in grass seed production fields because it germinates over an extended period, is difficult to selectively control, and its presence incurs seed cleaning costs. If growers time weed management practices before annual bluegrass produces viable seed, enduring control may improve. 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 (GDD0C; base 0°C) over three years and subjected them to germination testing. Annual bluegrass seed collected prior to 300 GDD were less likely to germinate compared to subsequent timings suggesting that a GDD model may improve weed management. Germination occurred up to 28 days, suggesting that the standard 21-day test may be inadequate to fully quantify germinability.

Technical Abstract: Annual bluegrass is a problematic weed in grass seed production fields because it germinates over an extended period, is difficult to selectively control, and its presence incurs seed cleaning costs. If growers time weed management practices before annual bluegrass produces viable seed, enduring control and a reduction of the weed seed bank may result. Research in eastern USA turfgrass systems 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 (GDD0C; base 0°C) over three years and subjected them to germination testing. The experimental layout was a randomized complete block experiment with four replications, where all annual bluegrass seed were collected from each plot and a subsample of seed was subjected to germination testing in a growth chamber. Data suggests that annual bluegrass seed collected prior to 300 GDD are less likely to germinate compared to subsequent timings suggesting that a GDD model may be used to improve weed management by grass production stakeholders in western Oregon. In 2024 and 2025, seed germination was recorded up to 28 days, suggesting that the standard 21-day germination test for annual bluegrass may be inadequate to fully quantify germinability of this species.