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An evergreen climber growing 6 to 10 ft high (but up to twice that height in favourable conditions); young shoots slightly warted, not downy. Leaves opposite, 3 to 5 in. long, pinnate, composed mostly of five or seven leaflets, the lowest pair rather near the stem. The side leaflets are ovate, 1⁄2 to 11⁄2 in. long, very shortly stalked, the terminal one lanceolate, 11⁄2 to 3 in. long, more slenderly pointed; all are of thin texture, quite glabrous except for a tuft of down at the vein-axils beneath, obliquely rounded or cordate at the base. Panicles axillary, many-flowered, 2 to 4 in. long, glabrous. Flowers very fragrant, white inside, rose-coloured outside in greenhouse plants but deeper-coloured in outdoor ones; the slender tube of the corolla3⁄4 in. long, spreading at the mouth into five obovate lobes, giving it a diameter of 3⁄4 in. Calyx 1⁄8 in. long with five erect, awl-shaped teeth nearly as long as the tube. Bot. Mag., t. 9545.
Native of Yunnan, China; discovered in 1883 by Père Delavay. Forrest found it flowering between May and August 1906 in the Tali valley and along the eastern flank of the Tali range up to 8,000 ft altitude, and also sent seeds before 1925, when the species was already cultivated at Kew (Gard. Chron. (Jan. 1939), p. 12). It did not become known to British gardeners until the Botanical Magazine figured it in 1938 from a spray sent by Captain de la Warre from his garden on the French Riviera. His plant was a gift from Major Lawrence Johnston, who had introduced it to his garden at Mentone in 1931 from Tengyueh in Yunnan, while collecting with Forrest. As the specific name implies, it is free-flowering, and the rosy or red colouring outside the corolla is unusual in the genus. It must have wall protection in a climate like that of Kew and is no doubt better suited for the south and west. Sometimes thirty to forty flowers are borne on a single panicle.
J. polyanthum is one of the finest of climbers for a cool greenhouse. It received an Award of Merit when shown from Kew in 1941 and a First Class Certificate eight years later.