Keep in mind when planting that Wood Nymph 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 Wood Nymph about 91 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Wood Nymph is a tender plant.