Description from Flora of China
Convolvulus marginatus Desrousseaux in Lamarck, Encycl. Meth. 3: 558. 1792; C. verrucosus (Blume) D. Dietrich; Ipomoea sepiaria Koenig ex Roxburgh; I. subtrilobans Miquel; I. verrucosa Blume.
Herbs perennial, with a stout root and spreading hirsute or glabrous axial parts. Stems twining or prostrate, 1-3 m. Petiole 1-3 cm, sometimes minutely tuberculate; leaf blade often purple or purple spotted, elliptic-ovate or reniform to circular, apical leaves sometimes sagittate or hastate, 2-6 X 2-5 cm, glabrous, ciliolate marginally, base deeply cordate or hastate, margin entire or minutely undulate, apex attenuate or ± abruptly acuminate. Inflorescences few to several flowered; peduncle 2-8 cm, thick, often applanate, verruculose distally; bracts persistent, ovate or oblong, ca. 2 mm. Pedicel 5-6 mm, sparsely verruculose. Sepals ovate or elliptic-oblong, equal or inner 3 longer, 4-7 mm, glabrous, apex obtuse; outer 2 verruculose, margin thinner. Corolla white or purple, with a darker center, ± salverform, 2.5-4 cm; lobes 5, apiculate. Stamens included. Pistil included; ovary glabrous. Stigma 2-lobed. Capsule depressed-globose, 6-7 mm, glabrous. Seeds pale grayish white tomentellous, margin often with longer cobwebby hairs.
Ipomoea marginata has often been misidentified as I. maxima (Linnaeus f.) Sweet.
Coastal or saline soils, thickets, grasslands, fields and waste areas. Hainan, Taiwan [India, Indonesia, Laos, Malaysia, Myanmar, New Guinea, ?Pakistan, Sri Lanka, Thailand, Vietnam; Africa, N Australia, Pacific Islands]