Oenothera perennis, or Sundrops, are 8 to 24" in height, and grow a single stalk or a stalk with a few branches. The flowers are yellow and similar to Evening Primrose, blooming early to mid-summer and lasting about a month. However, the flowers open during the day and close at night, the opposite of Evening Primrose. These plants like full to part sun, moist to dry, well-draining soil with sand or gravel.
 
The flowers are visited by bees, butterflies, and moths, and other insects feed on various parts of the plant. Naturalizes into meadows, forest edges, or along lakeshores, but does well in a garden setting as a border or in a rock garden. Great for the front of pollinator or butterfly gardens.