Plants shrub-like to subarboreous, usually densely clumping; rhizomes pachymorph, necks similar in length, up to 30 cm. Culms in a single dense to loose clump (unicespitose), to 7 m tall and 3.5 cm in diam., erect or curving at base, apically nodding to pendulous; internodes to 50 cm, terete, usually finely ridged, without fine purple spots, usually blue-grey with light persistent wax, becoming glossy; nodes scarcely to moderately raised. Branches 3--7 per mid-culm node at first, above promontory, subequal, deflexed, or basally erect but arching out, lateral branch axes lacking subtending sheaths; buds at mid-culm lanceolate, with 2 often very tall, single-keeled bracts, open at front (closed at culm base), 3--9 initials visible within. Culm sheaths usually long-triangular, papery and deciduous (rarely oblong, thickened and persistent); blades long, reflexed, deciduous. Leaf sheaths usually persistent; blade usually matt, thin, venation distinctly tessellate, either persistent or deciduous in winter. Synflorescence ebracteate, semelauctant; branching paniculate, erect, never unilateral, usually long-exserted from narrow subtending sheath, often fasciculate in dense panicles. Spikelets several-flowered; glumes basally loose, and frequently subtending reduced non-viable buds. Stamens 3. Stigmas 3. Named after Norman L. Bor, forester and grass taxonomist of the Indian Forest Service and the Royal Botanic Gardens Kew.
Borinda is a temperate to subtropical genus that currently contains 21 species, native to the Sino-Himalayan mountains from C Nepal to S Vietnam and W Sichuan. Many species have high local economic value and great horticultural potential. They are often indigenous to dwindling forest areas or individual mountain tops, and are thus potentially threatened with extinction as forests are cleared and climate change pushes species up the mountains.
Difficult to distinguish from Fargesia without flowers, but leaves are usually thinner, a fresher, matter green, and culms are usually finely ridged, with either longer and more triangular culm sheaths, or thickened persistent culm sheaths in the species with very deciduous leaf blades. Similar to Yushania but with shorter more consistent rhizomes, thus clump-forming not running, and with leaf blades arranged in a more regular fashion. Sometimes included in a broad interpretation of Yushania.
Most of the species have been described relatively recently, initially in Fargesia, and many further species in that genus are likely to require transferral. The genus cannot be included in Fargesia on grounds of morphology or phylogeny, but Borinda is often treated as part of Fargesia simply to keep all Borinda species in the same place. As many as 20 further species of Fargesia are likely to actually be Borinda instead, but this cannot be proven without flowers or DNA analysis.
The identification of a large number of new Borinda introductions remains problematic and may not be possible without more botanical fieldwork in their remote natural ranges.
Large stature hardy clump-forming bamboos are the holy grail of bamboo horticulture. Hardy species such as those in Fargesia and Thamnocalamus are rather small, while larger species such as those in Bambusa, Dendrocalamus, Drepanostachyum and Himalayacalamus are not sufficiently hardy. Therefore I was very excited to encounter Borinda grossa in the snow in Bhutan in 1985, growing taller than the houses, and producing substantial culms from well-behaved clumps which, unlike like those of Phyllostachys or Yushania, will not spread widely. Several species have since been introduced from Yunnan, Tibet, Nepal and Arunachal Pradesh. Both size and cold-hardiness vary substantially, often with an inverse relationship--the largest species having the least hardiness.
Several of the smaller, hardier species are very deciduous in winter. Although leaf blades of many bamboos can be lost under extreme conditions, and many bamboos shed a proportion of their leaves before winter, the routine annual fall of nearly all the leaf blades, as seen in several Borinda species, is unusual in the woody bamboos. Associated with thickened, more persistent sheaths and high altitude habitats up to 4000m, this would appear to be an adaptation to extreme cold and hence low water availability. The branching of these species is basally more erect, starting within the confines of persistent culm sheaths, and the internodes are flattened to slightly sulcate above the branches. None of these species have auricles or oral setae on the leaf sheaths.
Stapleton, C.M.A. (1998). New combinations in Borinda (Gramineae–Bambusoideae). Kew Bull. 53: 453–459.
Stapleton, C.M.A. (2000). New half-hardy bamboos from the Sino-Himalayan region. Amer. Bamboo Soc. Newsl. 21 (4): 16–21, with Bor biography
Stapleton, C.M.A. (2006). New taxa and combinations in cultivated bamboos (Poaceae: Bambusoideae). Sida 22(1): 331–332.