Perennial vine 1 - 2 m long Stem: trailing or twining, much branched, branches interwoven and twisted, sparsely short-hairy or hairless, and arising from a rhizome. If the stem is cut or broken, it exudes a milky sap. Leaves: alternate, stalked (stalks 2 - 5 cm long), non-toothed, appressed short-hairy, 3.5 - 9 cm long, longer than wide (2.5 - 9 cm wide at base), arrowhead-shaped with pointed tip, and two basal lobes spreading from the indented heart-shaped or u-shaped base. Flowers: many, usually paired in leaf axils, stalked (stalks strongly four-angled and winged, and shorter or equal to leaf stalk), pure white, showy, at least 5 cm long, radially symmetric, tubular to funnel-shaped. Each flower is immediately subtended by two overlapping, large (2 - 4 cm long, over 1.5 cm wide), non-toothed, inversely heart-shaped, pointed- or blunt-tipped bracts which hide the sepals. Sepals: five (but obscured by larger subtending bracts), hairless, 1 - 1.5 cm long, somewhat egg-shaped with rounded tips. Petals: five, but fused into a long tube with expanded to flaring limb, which may be shallowly five-lobed or merely wavy along edges. Stamens: five, attached to inside base of petal tube, then separating for 2.4 - 4 cm, but not extending beyond petal tube. Pistil: with one, single-chambered, superior ovary; and a single, slender style which ends in two oblong, blunt, and somewhat cylindric stigmas. Fruit: stalked, several-seeded, single-chambered, rounded capsules.
Similar species: Calystegia silvatica ssp. fraterniflora is very similar to C. sepium, except that species does not have winged flower stalks, the flower stalks are normally longer than the leaf stalks, the bracts are not as large or wide, and the flowers are rarely over 5 cm long. The other species of Calystegia in the Chicago Region are typically more erect herbs, and often have much smaller flowers.
Flowering: June to August
Habitat and ecology: Rare, typically a more southern plant, but supposedly along dry banks and in prairies.
Occurence in the Chicago region: native
Etymology: Calystegia is a combination of the Greek word kalyx meaning the whorl of sepals (calyx) of a flower, and stegon, meaning cover; together referring to the bracts that conceal the calyx. Sylvatica means "of the woods, forests". Fraterniflora is a combination of the Latin words for fraternal (brotherly or friend), and flora, thus "with brotherly flowers", referring to the fact that the flowers are usually in pairs.
Author: The Field Museum
From Flora of Indiana (1940) by Charles C. Deam
This [species] is rare in Indiana and has the habitat of the species [C. sepium].