Calendula is a perennial if accommodated but planted more commonly as an annual due to its sensitivity to extreme heat and frost. They typically reseed and come back annually. You can prolong their Spring and Summer blooms by picking flowers every few days or dead heading when their petals wilt, if allowed to seed they’ll stop blooming. They prefer well draining soil and will tolerate drying out between watering’s. They can be planted full sun in spring but will do better if they have partial shade relief in Summer.