Relationship between Planting Date, Growing Degree Days and the Winter Rye (Secale cereale L.) Variety “Rymin” in Minnesota

This study evaluated the influence of fall planting date on winter rye (Secale cereale L.) anthesis at three Minnesota locations for five dates from late August through October. This represents the time when fall-planted cover crops would likely be seeded in Minnesota. Earliness to anthesis is important in organic production systems where timing of rye management is affected by rye growth stage. The relationships among growing degree days (GDD), growth stage, and aboveground biomass were evaluated to predict how these factors influence anthesis date and how late in the fall rye could be planted without delaying anthesis. The study occurred in 2006 and 2007, which happened to have abnormally warm and cool growing seasons, with the earliest anthesis dates in 2007 being 25 May, 28 May, and 5 June at St. Paul, Lamberton, and Roseau, respectively, and dates in 2008 of 10 June, 11 June, and 17 June. Our results indicate that there was no fall biomass requirement but also that it was critical to accumulate at least 309 GDD in the fall so as not to delay spring anthesis. This information enables growers to choose appropriate planting dates for rye that will not delay anthesis. The optimal planting date corresponded to planting by late September (~20) in southern and early September (~8) in northern Minnesota.