Melocalamus yunnanensis

Synonyms: Racemobambos yunnanensis T. H. Wen, J. Bamboo Res. 5 (2), 1986: 11; Neomicrocalamus yunnanensis (T. H. Wen) Ohrnb., Bamb. World Intro. 4, 1997: 19.

Thai name: Not recorded.

Chinese name: 高肩梨籐竹 (gāo jiān lí téng zhú).

Distribution: THAILAND (North): Nan Province. — CHINA (South): Yunnan. — Perhaps also in LAOS.

Descriptions:

(1) "… pluricaespitose. Rhizomes elongated; pachymorph. Culms scandent; 1500 cm long; 10 mm diam.; woody. Culm-internodes terete; solid; 60 cm long; distally pubescent. Lateral branches dendroid. Branch complement many. Culm-sheaths deciduous; pubescent; with tawny hairs; glabrous on margins; without auricles; glabrous on shoulders. Culm-sheath ligule 1–3 mm high; ciliate. Culm-sheath blade inconspicuous, or linear; reflexed. Leaves cauline; 3–4 per branch. Leaf-sheaths 20–35 cm long; pubescent. Leaf-sheath oral hairs setose. Ligule an eciliate membrane. Leaf-blade base with a brief petiole-like connection to sheath. Leaf-blades lanceolate; 4–7 cm long; 8–13 mm wide. Leaf-blade venation with 8 secondary veins; without cross veins. Leaf-blade surface glabrous. Leaf-blade margins scabrous. Leaf-blade apex acuminate; filiform. … [flowers and seeds unknown]." — Kew GrassBase, as "Neomicrocalamus yunnanensis" [#1335].

(2) Y. X. Zhang, & al., New distribution records of two bamboo species in Yunnan, China with description of the inflorescence for Melocalamus yunnanensis (Poaceae, Bambusoideae), in PhytoKeys, 62, 2016: p. 41-56, fig. 1-6 [#1246].

(3) T. P. Yi, in J. Sichuan Forest. Sci. & Technol. 28(3), 2007: p. 18 [n.v.]. (4) T. H. Wen, in J. Bamboo Res. 5 (2), 1986: p. 11, fig. 1.

Images: Photos of specimens in KUN, mainly KUN 1248702. Photos of habitat and inflorescence in Y. X. Zhang & al., l.c., 2016: fig. 3 (p. 49).

Characteristics: Habit caespitose. Rhizome pachymorph. Culms erect below, bending above, scandent, not twining. Young shoots [not observed], emerge about April – August. Culm-internodes terete, (30) 50–70 (73) cm long, to 15 mm in diameter, green, glabrous; walls solid on the basal culm or with a small cavity, the cavity filled with pith (e.g., diameter 15 mm, wall 7 mm, cavity diameter 1 mm), walls thin on the mid-culm, cavity without pith (e.g., diameter 14 mm, wall 2.5 mm, cavity diameter 9 mm), walls relatively thick on the upper culm, cavity without pith (e.g., diameter 6.5 mm, wall 2.5 mm, cavity diameter 1.5 mm). Culm-nodes prominent; sheath scar a protruding broad dark girdle; supranodal line discernible or obscure, with a slight ridge; with a white ring below the sheath scar, with a white ring above (between the nodal line or sheath scar and the supranodal line, often hidden by remnants of the sheath scar); aerial roots none. Branch-buds present from the basal node up, prominent, pointed broad-ovate, broader than the diameter of the node. Branches: A single very dominant branch, in diameter (almost) as big as, or even somewhat bigger, and replacing the main axis, may develop on the lower and mid-culm; on the upper culm, numerous very slender branches, 0.5–1.5 mm in diameter, may develop; branching intravaginal or infravaginal (for development of a single thick branch on the lower or mid-culm nodes), and infravaginal and/or extravaginal (for development of multiple thin branches on the upper culm nodes); rebranching. Culm-leaves deciduous. Culm-leaf sheaths green, glabrous, much shorter than the internode; margins eciliate(?); apex bifid by two erect long triangular extensions, equal-sized and shaped, 1.5–2 cm long (on a culm with a diameter of 0.7 cm), these withering into a light straw color first and early. Culm-leaf auricles inconspicuous, rather long and very low rims, light green when young, without bristles. Culm-leaf ligule concave between both sheath extensions, green when young, short, entire(?) or denticulate(?), without bristles. Culm-leaf blades leaf-like, green when young, light straw-colored when dry, papery, caducous, reflexed, linear-lanceolate, as long as the sheath, or a little shorter, the junction with the sheath petiole-like and narrow; base cuneate; apex long attenuate(?), sometimes twisted. Foliage-leaves 9 per branchlet. Foliage-leaf sheaths light green when young, glabrous; margins eciliate. Foliage-leaf auricles inconspicuous or none, with a few long straight whitish very slender bristles, early caducous. Foliage-leaf ligule short, green, entire. Foliage-leaf blades soft, 11–17 (20?) × 1.5–2.5 (3?) cm, or slightly bigger, lanceolate, green and glabrous on both surfaces; base rounded to cuneate; apex attenuate; margins antrorsely scabrous; midrib proximally somewhat prominent beneath, light green; pseudo­petiole 2–4 mm long.

Cultivation requirements: Grows well in part shade in heavy normal moisture-retentive to moist soil with good drainage. Cannot tolerate floods; a 5-day flood in August 2020 caused significant damage to the plant.

Comments:

(1) An unusual and distinctive feature is the bifid apex of the culm-leaf sheath.

(2) This is the first record of the occurrence of Melocalamus yunnanensis (Wen) T. P. Yi in Thailand (Sarawood Sungkaew, pers. comm., Facebook, 2, 27, and 30 Oct. 2017).

(3) The plant BS-0902 grown at Bambusetum Baan Sammi died due to flooding in 2020. It reached a culm length of 13 m.