Check the whole field. The field average may be 30% seed color change, but there could be 2 to 3 different stages within the field. If half the field is just beginning seed color change, growers may want to hold off on swathing. By waiting 3 or 4 days, there is minimal risk of frost damage for riper parts of the field and a huge potential benefit for later parts if frost doesn’t occur. The graph below, based on Canola Council of Canada research, shows a yield increase of 11% when swathing is delayed from 30-40% seed color change to 60-70% seed color change.
If the field has distinct late and early parts, the two parts could be swathed at different times.
Finally, if the late parts of the field are not likely to mature even with an extra week of warm weather, the swathing decision should perhaps be based on what’s best for the plants that are mature. There is no “perfect” time to swath these uneven crops. At some point you have to decide the best time for the majority of plants in the field with the least negative impact possible on the rest.