Keep in mind when planting that Double Rosette Trumpet Collection 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.
By our calculations, you should look at sowing Double Rosette Trumpet Collection about 91 days before your last frost date.
As Double Rosette Trumpet Collection is tender, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.