Plants forming dense clumps. Rhizomes pachymorph, neck 2--5 cm long. Culms to 5 m, to 2 cm in diam., pendulous; internodes to 25 cm, terete, lightly blue-grey waxy at first, becoming pale green, longitudinal ridges very prominent, distally softly white appressed short-setose, wall very thin; nodes level, supra-nodal ridge absent, sheath scar thin; branches initially (3)-5-(7), strong, rebranching with up to 5 orders to give dense foliage. Culm sheaths very persistent, much longer than internode, papery, longitudinal ribs prominent, light green, light brown setose to base, apex narrow and loose, margins distally densely ciliate; auricles small, irregular; oral setae several, erect, 6-12mm; ligule to 3 mm, truncate or depressed, finely ciliate, tomentose; blade linear, glabrous, reflexed, quite persistent, margins usually glabrous. Leaves 4--8 per ultimate branch; sheath glabrous, margins glabrous; auricles absent; oral setae few to several, erect, wavy, ca. 5--8 mm; ligule convex, to 2 mm, tomentose; external ligule shortly white-ciliate; blade broadly lanceolate, to 16 × 2 cm, fresh mid-green, glabrous, base rounded, secondary veins 4-paired, margins distally spinescent-serrulate, transverse veins distinct. Synflorescence unknown. Name perlonga Latin, ‘very long’.
This species is characterised by very long, thin, persistent culm sheaths, as well as level nodes, and dense cascading foliage arising from 4-6 orders of branching, instead of the more modest degree of rebranching seen in most other Borinda species.
First introduced into the UK from 2,600m on Cang Shan in Yunnan Province of China in 1995 (Stapleton 1054) as Borinda perlonga, and in 1997 to the US and EU from the same mountain at 2950m, identified as Fargesia hygrophila. Similar plants were also sent to Holland (Yunnan 6) from an unknown locality, probably near Lushui. These 3 collections, all with very long culm sheaths, are kept under this name until further work on them has been undertaken. Further details are required from the cultivated plants, from the types representing the names, and from living plants in the localities where the types were collected. However, it would appear likely that Borinda hygrophila will be the correct name for the Cang Shan bamboo illustrated here, when that name has been published.