Description from Flora of China
Calystegia dahurica f. anestia (Fernald) Hara; C. japonica Choisy; C. japonica f. albiflora (Makino) Hara; C. japonica var. albiflora Makino; Convolvulus pellitus Ledebour f. anestius Fernald; Volvulus japonicus (Thunberg) Farwell var. pubescens (Lindley) Farwell.
Stems trailing or usually climbing, to several meters tall, glabrous to sparsely pubescent. Petiole 1--6 cm; leaf blade narrowly triangular to oblong, glabrous to sparsely pubescent, ± parallel sided at middle, weakly to strongly lobed at base but lobes not more than 1/3 length of midvein. Peduncles not exceeding leaf, glabrous or pubescent toward base; bracteoles 1.5--2.1(--2.4) X 0.8--1.4 cm, usually glabrous and obtuse. Corolla pink or rarely white, 4.2--6.7 cm. Stamens 2.4--3.2 cm; anthers 4.5--6 mm. Fl. Aug. 2n = 22.
The name Calystegia pubescens was given to a double-flowered form cultivated in Britain that is now naturalized in Europe and North America, which was originally collected near Shanghai. Normalflowered plants from this area were referred by Liou and Ling (Fl. Ill. Nord Chine p. 27. 1931) as C. japonica Choisy, but C. pubescens is the earlier name. In North America, Calystegia pubescens is commonly introduced and has often been misidentified as C. hederacea Wallich.
Plants intermediate between Calystegia pubescens and C. hederacea, from Japan, where they probably are sympatric, have been named as Convolvulus japonicus Thunberg ( =
Calystegia sepium var. japonica (Thunberg) Makino, non Calystegia japonica Choisy). Their status is in doubt.
Waste places, grassy or shrubby hillsides, sometimes a weed of cultivation. Beijing Shi, Heilongjiang, Hebei, Hubei, Jiangsu, ?Jilin, Liaoning, Shandong, Zhejiang [Japan, Korea; doubleflowered form introduced in Europe and North America]