Oenothera sect. Allochroa Fischer & C. A. Meyer, Index Seminum (St. Petersburg) 2: 44. 1836; Oenothera subg. Allochroa (Fischer & C. A. Meyer) Reichenbach

Capsules narrowly fusiform, [2–]3–4[–5] mm diam., sometimes enlarged in distal 1/3.

Species 20 (1 in the flora): introduced, California; South America.

Series Allochroa consists of 20 species, which are all native to South America, 16 of which are PTH, forming a ring of 14 chromosomes in meiosis. Unlike other species of Oenothera that are PTH, those of subsect. Munzia exhibit pollen fertility of over 90% and are maintained by selective fertilization (W. Dietrich 1977). Species of subsect. Munzia ser. Allochroa are widespread in South America with four species naturalized outside of their native range, three of which have been recorded in the United States: O. indecora Cambessèdes, O. mollissima Linnaeus, and O. stricta subsp. stricta. None of these species seems to be naturalized and the only one collected several times, and also the most recently collected, is O. stricta subsp. stricta, treated here. Oenothera mollissima was collected once in 1866 in ballast in Camden, New Jersey, once about 1920 in a shipyard in Linnton, Oregon, and three times in 1885 and 1900 at Port Eads, Louisiana. Similarly, O. indecora was collected once in Wilmington, North Carolina, in 1890. One additional species, O. villaricae W. Dietrich of subsect. Clelandia W. Dietrich, native to southern South America, has been collected once (in 1994) at Eglin Air Force Base, Florida; its status is not known.