The best two time of the year for planting poppy seeds are the Spring and the Fall. Poppies are a very hardy plant and they like the cold. They are different from other annual flowers, as they must be planted when the soil is still cool, 55 degrees Fahrenheit or less, to germinate properly.
For the Spring Planting, plant your seeds just after the last snow has fallen. If it does not snow where you live, plant the seeds in the middle of February.
For the Fall Planting, plant your seeds in the middle of September and prepare the soil as shown above. Poppies are very hardy; they should winter over just fine. However, just in case, save about half of your seeds for the Spring Planting.