Sundrops are perennials that blossom in the late spring and early summer in northern climates. They require little care and provide a wonderful display of bright yellow flowers. Although they are similar to the Evening Primrose, they are different in that their flowers close up at night. The red-hued stems grow in height from 15 to 24 inches. Some people find them invasive because of their ability to spread.
Sundrops can be started from seed planted directly into the ground or started indoors about six weeks before the last frost. They also can be purchased as established plants. They prefer sunny locations in soil that drains well. Plants should be spaced about 12 inches apart, and set into the ground at the same depth as the dirt enclosure in which they were purchased. If sowing the seeds outside, plant them about ¼ inch deep. Water well. Deadheading (removing wilted flowers) will not only improve the appearance, but will also result in more blossoms.