Cynanchum laeve
bluevine, bluevine milkweed, climbing milkweed, honeyvine, honeyvine milkweed, smooth swallow-wort
puberulent in single line;
dwarf axillary branches common (pseudostipules).
1–3 early-caducous stipular colleters on each side of petiole;
petiole 1–9 cm, puberulent in single line to glabrate;
blade pinnipalmately veined, ovate or deltate, 2–11 × 1.5–10 cm, chartaceous, base shallowly to deeply cordate or sagittate, with 3–8 laminar colleters, margins puberulent-ciliate or glabrate, apex acute, attenuate, acuminate, or apiculate, surfaces minutely puberulent to glabrate on veins.
racemiform to paniculiform, solitary (paired) at nodes, 6–30-flowered;
peduncle 0.2–2(–6.5) cm, puberulent in single line;
bracts caducous, 1, at base of each pedicel.
3–12 mm, tomentulose.
calyx lobes erect, lanceolate to ovate, 1.5–2 mm, apex obtuse, acute, or acuminate, puberulent to glabrate, margins ciliate to glabrate;
corolla cream, campanulate, tube 1–1.5 mm, lobes erect to spreading, plane to somewhat twisted, linear-lanceolate, 3.5–6 mm, glabrous, inframarginal adaxial ridges absent;
corona united to column near base, composed of 5 distinct segments, cream, laminar, slightly exserted from corolla, ovate with apex deeply divided into 2 subulate, usually twisted lobes, 4–6 mm;
style apex conic.
50–100, tan to light brown, 8–10 × 5–7 mm, thickly winged, chalazal margin erose, faces minutely foveolate;
coma white to tawny, 3–4 cm.
clear.
ovoid to lance-ovoid, straight to falcate, 7–15 × 2–3.5 cm, apex attenuate, thick-walled.
= 22.
Cynanchum laeve
Cynanchum laeve is a common and fairly weedy species from valleys west of the Appalachians to the central Great Plains. It is especially common in valleys of tributaries to the Mississippi River. It is far more evident as a weed on fences along roads, in fields, and in urban lots and gardens than in less-disturbed vegetation. Prior to massive anthropogenic environmental change in North America, the natural habitat was likely riparian vegetation. The deeply seated rhizomes are difficult to remove, and the vine is hard to eradicate from managed landscapes, where they are not necessarily unwelcome guests. The flowers are sweetly fragrant, hence the common name honeyvine. Cynanchum laeve has been reported from Ontario, but the author has not seen specimens to confirm its presence in the province. A report from Idaho is based on a misidentified specimen of Metaplexis japonica (Thunberg) Makino. Occurrences on the western and northern margins of the range and east of the Appalachians likely represent recent range expansion.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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