Bambusa sp. (AU)

Distribution: THAILAND: introduced, in cultivation, rare. — AUSTRALIA: in cultivation; supposed to originate from China.

Culm size: Height 13 m, diameter 6.5 cm; expected to reach a somewhat larger ultimate size.

Characteristics: Habit tight caespitose. Rhizome pachymorph, short-necked [n.v.]. Culms straight, erect, slightly bending above; 13 m tall [ultimate height not yet known]. Young shoots dark brownish-green, with dark brown hairs, conical, with the culm-leaf blades initially erect to slightly patent; emerge from July to December. Culm-internodes terete, 32–41 (47) cm long, dull mid-green, becoming dull light brownish with age mainly on the basal and lower culm, covered with appressed very short soft white, long-lasting hairs, nearly glabrous and rough when old, the basal and lower internodes whitish to light brown velvety; diameter 6.5 cm [ultimate diameter not yet known]; walls moderately thick on the basal and lower culm (walls 0.5 cm thick by an internode diameter of 2.3 cm), walls thin and internodes easily splitting on the mid-culm (walls 0.25 cm, diameter 1.9 cm) and the upper culm (walls 0.2 cm, diameter 1.3 cm). Culm-nodes glabrous, smooth, slightly prominent; sheath scar marginally protruding, 0–1 mm, with some early caducous brown soft hairs (remnants from the hairy sheath base); supranodal line discernible, with a slight ridge, 5–8 mm above the nodal line and forming a ring of white to light brown aerial roots on the basal and lower culm, the aerial roots to 6 mm long on the lowermost node, gradually shorter on the upper nodes, hard, usually not sharply pointed but somewhat thorn-like; with a whitish velvety ring, about 5 mm high, below the sheath scar when young, usually with a narrower white ring above the sheath scar when young. Branch-buds solitary, broad, 2 cm or broader. Branches from the basal nodes up, usually rudimentary and few on the basal and lower culm with a central branch remaining dormant, from the mid-culm up with a central dominant branch and several unequal smaller branches; branching intravaginal; rebranching. Culm-leaves early deciduous. Culm-leaf sheaths shorter than the internode, about 8 cm wide at the base, 16 cm long, coriaceous to thickly papery; light to dark brownish-green and almost glossy when young, dark-colored near margins when young, dull straw-colored when dry, sparsely covered with dark brown appressed hairs, mainly on the upper and middle part of the sheath, with early caducous furry brown hairs along the sheath base; initially thinly farinose(?); margins short dark to light brown ciliate when young; apex rounded to truncate, narrow, about 4 cm wide. Culm-leaf auricles about 1 cm wide rims, and 1–2 mm high irregularly shaped and outwardly bent dark-colored lobes, rims short brown fuzzy, with a few to several 5–15 mm long spreading slender pale bristles. Culm-leaf ligule 2–3 (5) mm high, dark purplish when young, dark brown when dry; margin irregularly shaped, cleft, or short-fringed, or denticulate, without ciliae. Culm-leaf blades often caducous, erect to deflexed on the mid and upper culm, horizontally deflexed on the lower culm, triangular on the basal and lower culm, lanceolate on the mid-culm and upper culm, adaxially hairy near the base, abaxially glabrous, rather short compared to the sheath length on the basal and lower culm; width of the junction with the sheath about half as wide as the sheath apex; dark purplish to dull dark brown to greenish brown when young, straw-colored and usually wrinkled when dry; margins convolute (on basal and lower culm); apex long pointed. Foliage-leaves (5) 8–12 (17) per branchlet. Foliage-leaf sheaths green when young, straw-colored when dry, often pale hirsute, sometimes glabrous; margins eciliate(?). Foliage-leaf auricles inconspicuous lobes, with a few pale bristles 8–15 mm long, or lobes and bristles absent. Foliage-leaf ligule 1 mm high or lower, reddish green when young, dark-colored when old, margin entire to subentire; outer ligule present, inconspicuous, callus-like. Foliage-leaf blades very variable in size, (6) 10–20 (30) × (1) 1.7–3.5 (4.5) cm, linear-lanceolate to lanceolate, mid-green above, pale green beneath, initially sparsely pilose above, glabrescent with age, puberulous beneath; base rounded to wedge-shaped, often asymmetrical; apex attenuate; margins antrorsely scabrous; midrib proximally slightly prominent and light green on both surfaces, side veins about 5 pairs, not tessellate; pseudopetiole 2–4 mm long, glabrous or pubescent. Flowers and seeds are unknown.

Images: Photos on Facebook, 1 Jan. 2018, as "Bambusa guangxiensis". Photos in BambooLand (trimmed habit), as "Bambusa guangxiensis"; BambooDownUnder (habit), as "Bambusa guangxiensis".

Uses: It has been reported that this bamboo could be used for low hedges (informal or trimmed), privacy screens, topiary, and landscaping, but the plants at Bambusetum Baan Sammi grew too tall and did not develop dense foliage; hence, they appeared not to be very suitable for trimmed hedges or topiary.

Cultivation requirements: Grows in part shade to full sun, prefers soils of 6.5 pH (mildly acidic) to 7.7 pH (mildly alkaline), sandy loam to clay loam, moisture-retentive, with good drainage; tolerates moderate wind; recorded to withstand frost to −2 °C; all those data are from Australian and US records.  The plant at Bambusetum Baan Sammi, Chiang Mai (300 m alt.), grows well on heavy soil in part shade to full sun.

Comments:

(1) Attempts to identify this bamboo have proven complex and contradictory and so far have not yielded a convincing result. "Growth habit: Very bushy, tight clumping" (BambooLand), which indicates the presence of a pachymorph rhizome, which is confirmed. However, a stated height of up to 5 or 6 (8) m cannot be confirmed, since the plant had already reached a height of 13 m at Bambusetum Baan Sammi. In addition, the stated culm diameter of 4 cm exceeded by 2 cm.

(2) Bamboo plants under the name Bambusa guangxiensis are offered in bamboo nurseries in Australia and the USA. The origin of this bamboo and how it got its name could not be traced back.

(3) Bambusa guangxiensis L. C. Chia & H. L. Fung, in Acta Phytotax. Sin. 18 (2), 1980: p. 214, Chinese name: 桂箪竹 (guì dān zhú), is described in the Flora of China [#1303] and Kew GrassBase [#1335]. The botanical name is based on Lingnania funghomii McClure, Lingnan Univ. Sci. Bull. No. 9, 1940: p. 36; type: Guangxi, 27 July 1937, H. Fung 21073 (LU). A photo of the type can be seen in the Chinese Virtual Herbarium [#1350], IBK00176583 (Guangxi Inst. Bot.). Neither the descriptions nor the photo support the identification of BS-0496 as Bambusa guangxiensis.

(4) The observed presence of thorn-like aerial roots (at least on the lower culm) and the late shooting season lead to the assumption that the species might belong to the genus Chimonocalamus. I was trying to key out the Chimonocalamus species using the information from the Flora of China (key, description, line drawing) and Kew GrassBase. However, BS-0496 does not match any Chinese species therein and only matches, to some extent, Chimonocalamus griffithianus from north-eastern India, but too many characteristics do not match, so that identification as a species of Chimonocalamus would be more than questionable. BS-0496 has not yet been compared with other Chimonocalamus species from north-eastern India and northern Myanmar.

(5) The tall growth height of BS-0496 alone, as well as the branch complement similar to Bambusa, make the identification as a Chimonocalamus species unlikely. An attempt to key out the species using the keys for Bambusa in the Flora of China [#1303] did not provide a convincing result. Hence, I am leaving BS-0496 provisionally as an unidentified Bambusa species.