Oenothera serrulata

Oenothera serrulata is a species of flowering plant in the Onagraceae known by the common name yellow sundrops. Other common names include halfshrub sundrop,^[3] serrate-leaved evening primrose, shrubby evening primrose, plains yellow primrose, and halfleaf sundrop.^[4] It is native to central North America, including central Canada and the central United States.^[1]

This plant is a subshrub that branches and forms a bushy clump up to 46 centimetres (18 inches) tall. The toothed leaves are up to 8.9 centimetres (3.5 inches) long. The yellow flowers bloom between March and November and have four petals.^[4] They open in the morning and close in the afternoon. They fade orange or pink with age. The fruit is a cylindrical capsule.^[3] It grows in dry, open plains and prairies.^[5]

This drought- and heat-tolerant species grows in many types of substrate, including caliche, limestone, and gypsum.^[3] The leaves turn so that their edges face the sun, an adaptation to hot conditions.^[4]

Oenothera serrulata was scientifically described and named by Thomas Nuttall in 1818. It is classified in the genus Oenothera within the Onagraceae family. It has no accepted subspecies or varieties, but it has 27 synonyms according to Plants of the World Online.^[2]