Seasonal changes in annual bluegrass (Poa annua) germinability and emergence

Abstract

Abstract The seasonal emergence characteristics and seedbank ecology of annual bluegrass were evaluated in a vegetable field in the central coast of California. The emergence and germinability of annual bluegrass were monitored continuously for over 3 yr to detect seasonal variation in weed emergence. Weed emergence and seedbank densities were measured every 45 d for 41 mo. Weed emergence was monitored simultaneously in the field and in a growth chamber that was adjusted seasonally for day length and temperature. Samples were incubated in the growth chamber for 45 d and then elutriated to measure remaining viable ungerminated caryopses and relative germination potential. Seedbank densities ranged from 2,000 to 20,000 caryopses m−2 during the study period. Weed emergence and germinability were highest from October to November and lowest from March to July. Emergence from soils collected in the spring and fall and incubated under both spring and fall conditions in the growth chamber indicated that seed dorm...