Keep in mind when planting that Preussen is thought of as tender, so remember to wait until your soil is warm and the night time temperature is well above freezing before moving outside.
Growing Preussen from seed
By our calculations, you should look at sowing Preussen about 91 days before your last frost date.
Transplanting Preussen
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Preussen is a tender plant.