Cynanchum laeve
Cynanchum unifarium
bluevine, bluevine milkweed, climbing milkweed, honeyvine, honeyvine milkweed, smooth swallow-wort
talayote
puberulent in single line;
dwarf axillary branches common (pseudostipules).
puberulent in single line or glabrate;
dwarf axillary branches rare.
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.
1 stipular colleter on each side of petiole;
petiole 1–7 cm, densely puberulent in single line;
blade pinnipalmately veined, ovate to deltate, 3–11 × 1.5–9 cm, chartaceous, base shallowly to deeply cordate or sagittate, with 2–6 laminar colleters, margins puberulent-ciliate, apex acute, attenuate, acuminate, or apiculate, surfaces sparsely puberulent on veins abaxially and adaxially.
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.
racemiform to corymbiform, solitary at nodes, 4–20-flowered;
peduncle 0.6–3.5 cm, densely puberulent in single line;
bracts caducous, 1, at base of each pedicel.
3–12 mm, tomentulose.
4–12 mm, densely puberulent in single line.
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.
calyx lobes ascending to spreading, lanceolate to oblong, 2–3 mm, apex acute, ciliate;
corolla green with lobe margins and apex white, shallowly campanulate to campanulate-rotate, tube 0.5–1 mm, lobes ascending to spreading with recurved tips, oblong, 3–4 mm, glabrous, with thickened inframarginal ridges adaxially;
corona united to column near base, composed of 5 segments connate at base, cream, laminar, included in corolla, quadrate, apex shallowly 3-lobed, central lobe equal to lateral lobes or extended as triangular tooth up to 8 times length of lateral lobes, 1–2 mm;
style apex convex.
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.
50–100, brown, 6–8 × 4–5 mm, narrowly winged, chalazal margins erose, faces minutely papillate;
coma white to tawny, 2.5–3.5 cm.
clear.
white.
ovoid to lance-ovoid, straight to falcate, 7–15 × 2–3.5 cm, apex attenuate, thick-walled.
ovoid, 8–12 × 1.5–2.5 cm, apex obtuse, thick-walled.
= 22.
Cynanchum laeve
Cynanchum unifarium
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.)
Cynanchum unifarium occurs in a great diversity of habitats from southern to western Texas and is one of the most commonly encountered milkweed vines in the state. It is most commonly found in riparian vegetation but can occur in a wide variety of plant communities on diverse substrates. Cynanchum unifarium was included in a broadly circumscribed C. racemosum (Jacquin) Jacquin by E. Sundell (1981). This approach has merit, but the narrower concept used by W. D. Stevens (2009) is adopted here until this complex receives more detailed study. The Spanish common name derives from an Aztec word that is commonly applied to diverse milkweeds across Mexico, including those in the genera Asclepias, Gonolobus, Marsdenia R. Brown, Matelea, and Polystemma, among others.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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