Keep in mind when planting that Serena is thought of as hardy, so it can be safe to leave outdoors for the majority of winter (although if in doubt, using a row cover is often a good idea).
Growing Serena from seed
By our calculations, you should look at sowing Serena about 90 days before your last frost date.
Transplanting Serena
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Serena is a hardy plant.