A new morning glory, Calystegia felix Provance & A.C. Sanders sp. nov. (Convolvulaceae), is described from the Los Angeles, San Gabriel, and Santa Ana River basins. Historical collections of the species, which prior to 2011 had not been seen alive in 94 years, have been misidentified as Calystegia sepium (L.) R. Br. subsp. binghamiae (Greene) Brummitt. The undescribed species was rediscovered in the City of Chino in April of 2011, a few miles north of the location where the most recent previous collection had been made by I. M. Johnston in 1917. The plants were found just prior to their likely destruction by grading and trenching for an underground power line. Intensive searches have resulted in the discovery of five additional occurrences, all of them in the City of Chino. Calystegia felix is at high risk of soon becoming extinct in the wild. All of the known extant occurrences are associated with well-watered landscaping on recently completed industrial, commercial, and residential developments. Every known living occurrence is within the limits of a ciénega belt, which is now mostly historical. Otherwise, the new species is only known only from collections made around the turn of the 20th century in what are now heavily urbanized areas, including one from South Los Angeles and another from Pico Rivera in Los Angeles County. Calystegia felix lacks the large bracts that immediately subtend, and enclose the calyx, which are always present in members of the C. sepium complex. Affinities to C. felix are found among other western US species with graduated sepals and small, often somewhat remote bracts. We discuss the enduring confusion between C. felix and C. sepium subsp. binghamiae, and differentiate the new species from some of its more likely relatives. The taxonomic treatment is supplemented by photos of herbarium specimens and living plants. We also discuss the ecological setting of Chino’s ciénega belt, which was a mosaic of palustrine wetlands.
