Flower-of-an-Hour (Hibiscus trionum)
Beautiful little Hibiscus flowers that last only a short time once they open (thus the common name). This plant came to the New World as a garden favorite, but has made itself at home in the most inhospitable places: this plant grew through the gravel at the edge of a gravel parking lot near Cranberry, where it was blooming at the end of September.
Gray describes the genus and the species:
HIBÍSCUS L. ROSE MALLOW. Calyx involucellate at the base by a row of numerous bractlets, 5-cleft. Column of stamens long, bearing anthers for much of its length. Styles united, stigmas 5, capitate. Fruit a 5-celled loculicidal pod. Seeds several or many in each cell. — Herbs or shrubs, usually with large and showy flowers. (An old Greek and Latin name of unknown meaning.)
H. triònum L. (FLOWER-OF-AN-HOUR.) A low rather hairy annual; upper leaves 3-parted, with lanceolate divisions, the middle one much the longest; fruiting calyx inflated, membranaceous, 5-winged, with numerous dark ciliate nerves; corolla sulphur-yellow, with a blackish eye, ephemeral.—Cultivated and waste ground, rather local. (Nat, from Eu.)