Description from Flora of China
Calonyction grandiflorum (Jacquin) Choisy; C. jacquinii G. Don; C. tuba (Schlechtendal) Colla; Convolvulus grandiflorus Jacquin; Convolvulus tuba Schlechtendal; Ipomoea glaberrima Bojer ex Bouton; I. grandiflora (Jacquin) H. Hallier; I. longiflora R. Brown; I. macrantha Roemer & Schultes; I. tuba (Schlechtendal) G. Don.
Plants perennial, woody, twining, glabrous. Stems to 5 m, often longitudinally wrinkled. Petiole 3.5-11 cm; leaf blade circular or ovate, 5-16 X 5-14 cm, base deeply cordate; lobes rounded or rarely angular, apex acuminate, mucronulate; lateral veins 7 or 8 pairs. Inflorescences 1- to few flowered; peduncle often 2.5-4.5(-7) cm. Pedicel 1.5-3 cm, thickened and clavate in fruit. Flowers nocturnal. Sepals ± circular, equal or outer 2 shorter, 1.5-2.5 cm, thinly leathery, apex obtuse or emarginate, mucronulate, enlarged in fruit and reflexed. Corolla white, with green midpetaline bands, salverform, 9-12 cm; limb 8-10 cm in diam. Stamens included; filaments inserted near base of corolla tube. Pistil included; ovary glabrous. Stigma 2-lobed. Capsule pale brown, ovoid to ± globose, 2-2.5 cm, glabrous. Seeds black, 1-1.2 cm, densely short tomentose, edges with ca. 3 mm long sericeous hairs. 2n = 30.
Beaches, seaside thickets, edges of brackish rivers and lagoons; near sea level to 100 m. Guangdong, Hainan (Nanhai Zhudao), Taiwan [Indonesia, Japan, Malaysia, New Guinea, Philippines, Sri Lanka, Thailand; Africa, N Australia, North America, Pacific Islands, South America].