Ryegrass is planted as a pure strain or used in grass seed mixtures depending on the specific lawn, pasture or turf use desired. Ryegrasses are adapted into lawns mainly for their fast growing ability as a cool season grass and is sometimes referred to as winter rye grass.Ryegrass, grow best when the soil temperatures are between 50 and 65 degrees F. These temperatures usually occur when the daytime air temperatures are between 60 and 75 degrees.