Plants forming dense clumps. Rhizomes pachymorph, neck to 12 cm. Culms to 5 m, 1–2 cm in diam.; internodes to 18 cm, cylindrical, very smooth, basally white-powdery initially, becoming red-brown with exposure or yellow-brown, wall thick; nodes with light supra-nodal ridge, sheath scar inconspicuous, shortly tomentose, branches initially 5–9. Culm sheaths persistent, much longer than internode, narrowly triangular, basally leathery, distally papery, brown to dark-brown setose at first, yellow-brown with dense purple-brown spots around each seta, distally glabrous, margins very shortly ciliate, apex of new shoots slightly inflated; auricles absent; oral setae few, erect, deciduous; ligule ca. 1 mm, truncate, tomentose, densely long-fimbriate to 1.5 cm; blade deciduous, linear-lanceolate. Leaf sheath shortly tomentose, overlapping margin initially apically ciliate to oblique rising shoulder, inner margin glabrous to level shoulder, shoulders more level on basal sheaths; auricles absent; oral setae erect, to 6mm, white, dense, persistent; ligule truncate, ca. 0.5 mm, shortly ciliate by overlapping margin to fimbriate by inner margin, tomentose; external ligule to 0.3 mm, glabrous, minutely ciliate; blade narrowly lanceolate, 10–14 × 0.8–1.2 cm, base cuneate, abaxial tomentose to proximally densely pilose beside midvein, adaxial glabrous to sparsely shortly pilose, secondary veins 4-paired, transverse veins distinct; petiole pilose. Name from the Latin fungus, ‘mushroom or sponge’ referring to well-developed spongy pith within the culm internodes.
Striking change of fimbriation on ligule vs. shoulders from culm sheath to leaf sheath. Substantial differences noted by Dr. J.-P. Demoly (who considers this to be a species of Yushania), between the description of Fargesia fungosa by T.P. Yi and the plants cultivated from seed sent by Prof. Xue under that name. These are tabulated in Bull. “Bambou” de l’A.E.B.-n°hors série- 2006. A detailed comparison of B. fungosa in the type locality with the species cultivated as such would be very useful.
Well suited to the drier warmer climates of central Yunnan and California, B. fungosa has not thrived in N Europe. Intolerant of cold wet soil as a young plant, most seedlings in the UK died, but the few that survived have eventually proven more resilient once established. Seedlings grown in California varied in leaf and culm size. Many had white variegation on the leaves, and these can be a stunning sight in a shady location. The culm colour also varied between seedlings, and some clones with a tendency to produce darker, chocolate-brown culms after exposure have been selected.
Borinda fungosa seed was collected in Yunnan by Prof. Xue Ji-Ru (J.R. Hsueh) of SWFC in Kunming, the renowned bamboo taxonomist who worked closely with Prof. T.P. Yi, together describing many new species of bamboo. Seed was given by him to Karl Bareis for the US in 1989, and to Charlie Young in Holland.