The winter test is necessary to determine eligibility for re-certification of the lot. However, excessive amounts of virus make the lot unacceptable for certification. Virus is the main factor, but other factors such as mixture, herbicide damage, vigor and other diseases may cause the lot to be rejected for re-certification; all of which are determined during the winter test process carried out annually in early January.

North Dakota’s post-harvest test takes place in Homestead, Florida near Miami. The test is performed on land owned by the North Dakota Certified Seed Growers Association. Representative seed samples are shipped to Homestead in the first week of November, and planted approximately 1-2 weeks later.

In early January, Department officials perform field inspections on the growing samples in a manner that approximates summer field inspections. Laboratory testing is also done in a similar manner to summer inspections, especially on varieties known to mask virus symptoms. Final passage of lots provide information to North Dakota and other state programs on the eligibility of seed lots for planting and certification the following season. A Winter Test Directory is provided to anyone interested in eligible seed lots.