Description from Flora of China
Herbs, perennials, with erect stems tufted from rootstock and from subterranean rhizomes; lower stem portions quadrangular, broadly winged, upper with wings reduced, retrorsely aculeolate. Leaves in whorls of 4-6; petiole 0.5-1 cm; blade drying leathery, ovate, 1-2 × 0.5-1 cm, both surfaces sparsely scaberulous to aculeolate, base cordate, margin revolute and aculeolate, apex cuspidate-acuminate; principal veins 3, palmate, with lateral veins extending for ca. half of blade length. Inflorescences thyrsoid, with terminal and axillary, several-flowered and 1.5-2.5 cm long cymes; axes retrorsely aculeolate with reduced bracts; pedicels filiform, 1-2 mm. Ovary ca. 1 mm, smooth. Corolla dried dark brownish, rotate, ca. 2.5 mm in diam., glabrous; lobes lanceolate-ovate, 1-1.2 mm, cuspidate. Mericarp berry unknown. Fl. Jun.
No authentic material of Rubia pterygocaulis was available, but a good drawing (including underground organs) is found in H. S. Lo (in FRPS 71(2): 300, t. 65, f. 1-9. 1999). The local taxon evidently is a somewhat xerophytic member of R. ser. Cordifoliae.
● Forests, thickets; 300-1000 m. Sichuan (Jiuzaigou).