Keep in mind when planting that Petticoat Frills is thought of as tender, so it is really important to ensure that the outside temperature is well above freezing before planting or moving outdoors.
By our calculations, you should look at sowing Petticoat Frills about 91 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Petticoat Frills is a tender plant.