Thurstonii is generally regarded as a tender plant, so remember to wait until your soil is warm and the night time temperature is well above freezing before moving outside.
Growing Thurstonii from seed
By our calculations, you should look at sowing Thurstonii about 91 days before your last frost date.
Transplanting Thurstonii
Thurstonii is tender, so ensure you wait until all danger of frost has passed in your area before considering planting outside.