Description from Flora of China
Convolvulus obscurus Linnaeus, Sp. Pl. ed. 2., 2: 220. 1762; Ipomoea insuavis Blume; I. luteola R. Brown.
Herbs twining; axial parts glabrous, spreading pubescent, or almost woolly. Stems thinly angular, 1-2 m. Petiole 1.5-3.5 cm; leaf blade cordate-circular or ovate, occasionally reniform, 2-8 X 1.6-8 cm, glabrous or sparsely pilose, base cordate, margin entire or minutely undulate, apex attenuate, acute. Inflorescences 1-3-flowered; peduncle almost filiform, 1.4-4 cm; bracts subulate, ca. 1.5 mm. Pedicel 0.8-2 cm, subglabrous, thickened and recurved in fruit distally. Sepals reflexed in fruit, elliptic-ovate, subequal, 4-5 mm, glabrous or ± pubescent, mucronulate, outer ones whitish margined. Corolla white or pale yellow, with darker midpetaline bands and a purple center, funnelform, 2-2.5 cm. Stamens included; filaments very unequal. Pistil included; ovary glabrous. Stigma 2-lobed. Capsule conical-ovoid or ± globose, 6-8 mm in diam., apiculate. Seeds black-brown, 4-5 mm, densely gray-brown tomentellous. 2n = 30.
Weedy in thickets, open forests, sandy places, seashores; 0-1600 m. Guangdong, Hainan (Nanhai Zhudao), Taiwan, Yunnan [Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, New Guinea, ?Pakistan, Philippines, Sri Lanka, Thailand, Vietnam; E Africa, N Australia, Pacific Islands].