Vascular Plants of North Carolina
Account for Twin-flowered Bindweed - Convolvulus fraterniflorus   (Mackenzie & Bush) Mackenzie & Bush
Members of Convolvulus with account distribution info or public map:
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Section 6 » Family Convolvulaceae
Author(Mackenzie & Bush) Mackenzie & Bush
DistributionThe former Calystegia sepium from RAB (1968) has now been split out into several species, not to mention all now in the genus Convolvulus. Thus, many specimens labelled as C. sepium have probably not been sorted or moved into the new species. For now, the website editors have mapped records to the Piedmont and the adjacent northwestern Coastal Plain. This species does not seem to be present in the mountains, and in most of the Coastal Plain.

Weakley (2018) shows the range being somewhat northern, ranging south to SC, northern GA, and AR.
AbundanceThough Weakley (2018) shows the species as "rare" in the Piedmont and Coastal Plain, and absent in the mountains, on his range map, the specimen data suggest that the species is not truly rare in the Piedmont. It is best stated as rare to uncommon in the Piedmont, and rare in the adjacent northwestern Coastal Plain. The website editors suggest a State Rank of S3?, and no watch list at the present time.
Habitat"Thickets, roadsides, fields, streambanks, disturbed areas" (Weakley 2018).
PhenologyBlooms from April to September, and fruits shortly after flowering.
IdentificationMembers of the former Calystegia sepium (now Convolvulus) complex -- C. americanus, C. fraterniflorus, C. limnophilus, and species 2 -- all are herbaceous vines that range to about 12' long or more, and they are also strongly twining. The large alternate leaves are mostly arrowhead-shaped to triangular, with long tips and heart-shaped or more often squared-off leaf bases. Flowers are mostly in the middle and upper leaf axils and are quite large, funnel-shaped, about 2-3" long and across, either white or pink with yellow deep in the throat. C. fraterniflorus differs from the other three by the "margins of the bracts immediately subtending the flower overlapping > 1/2 their length; bracts inflated at base (saccate), the apex usually obtuse; flowers 1-2 per axil" (Weakley 2018) -- versus "margins of the bracts immediately subtending the flowers overlapping at the base only or not at all; bracts mostly flat (or often keeled), the apex usually acute; flowers 1 per axil" in the others. Of this latter group, only C. limnophilus has white flowers, whereas C. americanus and C. species 2 have pink flowers. These latter two are separated by "Leaves with basal lobes rounded or with a single angle, or if with 2 angles then not spreading; plant glabrous or commonly pubescent to tomentose on stem" (Weakley 2018) for C. americanus -- versus "Leaves with lobes with 2 angles, spreading; plant glabrous" for C. species 2. In summary, this should be the only member of the group found in the Piedmont, and it should be identified by its large white flower with yellow in the throat. Where it may overlap in the Coastal Plain with C. limnophilus, which also has white flowers, see if it has two flowers in an axil (which only C. fraterniflorus has); otherwise, you need to check the bracts of the flowers.
Taxonomic CommentsSee Distribution. This taxon is not recognized by NatureServe.

Other Common Name(s)Shortstalk False Bindweed
State Rank[S3?]
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H. LeGrandConvolvulus fraterniflorus; Wake Co.; Fred Fletcher Park, Raleigh; edge of wet thicket; 21 August 2019 WakePhoto_natural
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