Description from Flora of China
Cynanchum szechuanense var. albescens Tsiang & Zhang.
Plants pubescent or pilose except for corolla. Stems twining, to 6 m, pubescent along 1 side. Petiole 1.5-5.5 cm; leaf blade ovate or triangular-ovate, 3.2-13(-23) × 1.5-8.5
(-13.5) cm, papery, adaxially minutely appressed puberulent, abaxially pubescent on veins, base deeply cordate with basal lobes sometimes incurved and rarely slightly enlarged, apex acuminate; basal veins 5-7, pedate, lateral veins 2 or 3 pairs. Inflorescences long, simple or with short lateral branches; cymules distinct, many flowered, umbel-like or ± contiguous, few flowered, and racemelike; peduncle 4-8(-12.5) cm, rachis 0-7 cm. Sepals lanceolate, ca. 3.5 × 1 mm; basal glands present. Corolla green or white with purple apex, rotate to reflexed, tube short; lobes lanceolate, 3.5-5.5(-6.7) × 1.4-2 mm, glabrous outside, pubescent inside. Corona white, tube cupular, 1.3-2.5 mm high, membranous, margin with 5 main lobes, these triangular to threadlike, 1.2-3 mm, sinuses between these each usually with ca. 3 small rounded teeth, sometimes ± truncate; inner appendages lanceolate to threadlike, as long as or exserted from tube. Anther appendages rounded; pollinia oblong. Stigma head conical. Follicles lanceolate in outline, 7.5-9 × ca. 1.5 cm. Fl. May-Jul.
Cynanchum szechuanense is quite variable in the length of corona lobes. Forms with the longest lobes are restricted to W Sichuan but those with short triangular lobes are found throughout the species range. Further studies are needed to show if infraspecific taxa can be recognized.
* Open woodland, climbing over shrubs; 2300-3200 m. W Sichuan, Xizang