Keep in mind when planting that Cottage terracotta 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. Cottage terracotta needs a sandy, loamy and clay soil with a ph of 5.6 to 6.0 (weakly acidic soil).
By our calculations, you should look at sowing Cottage terracotta about 105 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Cottage terracotta is a tender plant.