Loasaceae : Mentzelia decapetala

Mentzelia decapetala is a coarse, erect, shrubby looking, biennial to weakly perennial herb growing up to 1 m tall. There are 1 to several stems that branched above, and the lower stems develop a whitish, exfoliating bark. The leaves are alternate, fleshy, lanceolate, 4-15 cm long, 1.5-4 cm wide, pinnatifid with wavy lobes, the lower leaves petiolate and the upper sessile. The flowers are solitary or in small clusters at the ends of branches. The 5 sepals are 1-5 cm long with pointed tips, and the 10 petals are white to cream colored, 5-7 cm long and 1-2 cm wide, oblanceolate to spatulate and often overlapping. There are numerous stamens that are shorter than the petals and form a yellow center in the opened flower. When open, the petals create a showy display, each flower up to 15 in diameter. The flowers open in late afternoon and close around midnight. The fruit is a cylindrical capsule 3-5 cm long and 1,5-2 cm wide with numerous, flattened, minutely winged seeds. Ten-petal blazingstar blooms from July into September along roadsides, and other disturbed places, including the Missouri River drainage, scattered throughout South Dakota.