14. Hibiscus grandiflorus Michaux, Fl. Bor.-Amer. 2: 46. 1803.
Swamp rose-mallow Swamp rose-mallow
Hibiscus urbanii Helwig
Herbs, perennial, to 3 m. Stems glabrous or rarely stellate-hairy on younger parts, without line of minute, curved length 1/2–1 times petioles, glabrate or finely hairy; involucellar bractlets 9–13, linear-subulate, 1.3–2.7 cm, margins not ciliate, velvety-hairy. Flowers horizontal or ascending; calyx divided to ± middle, broadly campanulate, 2.9–6 cm, larger in fruit, lobes triangular, apices acute to subcaudate, velvety-hairy, nectaries absent; corolla broadly to narrowly funnelform, petals pale pink to white, red basally, narrowly obovate, usually not conspicuously overlapping, 8.5–14 × 4–8.5 cm, apical margins repand, finely hairy abaxially where exposed in bud; staminal column straight, pink to white, 6.2–9.5 cm, length 2/3 petals, bearing filaments throughout its length, free portion of filaments secund, 3–9 mm; pollen yellow; styles white, 7–17 mm; stigmas yellow. Capsules light to dark brown, ovoid to subglobose, 2.2–3.5 cm, apex apiculate, hispid with simple, yellowish-brown to reddish-brown hairs. Seeds brown to reddish brown, reniform-globose, 2.8–3.1 mm, verrucose-papillose. 2n = 38.
Flowering (May–)Jun–Aug(–Sep). Freshwater and brackish marshes; 0–20 m; Ala., Fla., Ga., La., Miss., S.C., Tex.; West Indies (w Cuba).
The flowers of Hibiscus grandiflorus first open in the evening, emit a pleasant fragrance, and are pollinated by sphingid moths (O. J. Blanchard 1976). It is relatively common only in Florida. Hibiscus grandiflorus is sometimes cultivated and has been found to be hardy as far north as Illinois (S. R. Hill, pers. comm.).