Calystegia Species, Downy Calystegia, Short Haired Calystegia

Calystegia pubescens may sometimes present as glabrous but plants grown in the warmer zones will often display a healthy (and happy) pube...Read Morescence , so if the plants display any (significant) pubescence they cannot be Calystegia hederacea.

C.hederacea is always completely glabrous in contradistinction to Calystegia pubescens in which a fine pubescence may occur.

FOC Vol. 16 Page 288
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.

Normal flowered 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.

Calystegia pubescens also produces a double flowered form
which has had the wrong epithet applied as perpetuated by the
horticultural societies who seem to be oblivious regarding the ability to differentiate distinct species with the genus Calystegia.

Here are the 2 other PlantFile entries where this same plant is 'traditionally' mis-described as Calystegia hederacea.
Calystegia hederacea 'Flore Pleno
http://davesgarden.com/guides/pf/go/56485/

Japanese False Bindweed
Calystegia hederacea ( the double flowered forms)
http://davesgarden.com/guides/pf/go/160132/

The typical absence of high quality macro photos elucidating the important identifying leaf surface characteristics casts a serious shadow of doubt on the accuracy of the epithets as commonly 'used' by horticultural merchants and supposed 'professional' organizations.