What is the best time to plant milkweed seeds?

Pollinator Plants of the Central US provides an overview of milkweed establishment practices for the lower Midwest and central United States. According to the document, milkweed seed should ideally be planted in the fall. While some seed predation will occur, exposure to cold temperatures and moist conditions during winter will stimulate germination. Spring planting is also possible but artificial stratification of the seed is recommended to enhance germination.