Crabgrass Germinating?

04/08/2013

Once the first warm days arrive, the topic of discussion becomes crabgrass. Crabgrass emergence is often associated with phenological events like 1) flower withering of Forsythia or the initiation of flowering by dogwoods. Watching for germination of crabgrass in cracks in pavement can serve as a key to emergence in turf is not far off (although these early germinating plants are susceptible to a cold and usually die with the arrival of a cold snap). Other crabgrass emergence keys are based on soil temperatures. Mike Fidanza and Peter Dernoeden at the University of Maryland proposed the following from their research (Fidanza, M.A., P.H. Dernoeden, and M. Zhang. 1996. Degree-days for predicting smooth crabgrass emergence in cool-season turfgrasses. Crop Science 36:990-996.)

Ave. Min. soil temp. at which initial appearance is observed -54 F

Ave. mean soil temp. at wich initial appearance is observed - 60 to 64F

Ave. Min. soil temp. at which major emergence occurs - 60 to 70F

Ave. mean soil temp. at which major emergence occurs - 73 to 75 F