Gigantochloa sp. (TH) 1

Gigantochloa sp. (BS-0602): Apex of the young shoot, a section of a young shoot showing a culm-leaf with blade and auricle, culm-leaf blade of a young shoot, culm-node showing a white ring below the sheath scar, culm-leaf when old (from left to right)

• • Characteristics:

  • (1)  Habit caespitose. Rhizome pachymorph. Culms erect, bending above, unbranched on the basal culm (branched from about the 5th node above the ground). Young shoots dark hairy, with culm-leaf blades stiffly erect; emerge from March. Culm-internodes 22–40 cm long, mid-green when young, dark green and rough when old, initially with a few loosely scattered short black rigid hairs, occasionally with a few narrow yellowish stripes on the basal culm; diameter 2.6 cm (in an immature and disturbed, 6-year-old plant); wall thickness not yet observed. Culm-nodes not prominent; sheath scar glabrous, with a narrow white ring below when young; nodal ridge inconspicuous. Branches several, the central one dominant, with 2 side branches subdominant, and a few smaller branches; branching intravaginal. Culm-leaves leathery, late deciduous. Culm-leaf sheaths 14–15 cm long on the lower culm, about half as long as the internode, mid-green when young, straw-colored when dry, covered with short rigid black hairs; margins black ciliate when young, entire when dry; apex obliquely rounded or almost oblique-truncate, 2–2.5 cm wide. Culm-leaf auricles lobe-like, rounded or oval-shaped towards the edge, about 4–6 mm wide, 2–3 mm high, entire, glossy, and dark green when young; oral setae none. Culm-leaf ligule low, about 1 mm, denticulate, or initially ciliate(?). Culm-leaf blade erect, rarely caducous, lanceolate, 4–7 × 1.2–2 cm on the lower culm, dark green and narrowly striped when young; the attachment with the sheath about 1.5 cm wide; apex acuminate, occasionally twisted when dry. Foliage-leaves (4) 6–8 (9) per branchlet. Foliage-leaf sheath mid-green, initially hispid(?), glabrous when old; margins eciliate(?). Foliage-leaf auricles small, rounded, entire; oral setae none. Foliage-leaf ligule inconspicuous. Foliage-leaf blades (14) 28–31 (36) × (2) 3.2–3.7 (4.3) cm, glabrous on both surfaces, dark green; margins antrorsely scabrous; base rounded to cuneate; apex attenuate; midrib proximally prominent beneath; pseudopetiole 2–3 mm long.

  • (2) Culm size: Diameter increasing with height, gradually increasing from the base to the lower mid-culm up to 20% (e.g., basal diameter 2.5 cm, diameter 3.0 cm on the 8th internode at 2.0 m above the ground), then remaining constant for several meters and gradually decreasing towards the top. A culm diameter that increases with the culm height between the base and the lower mid-culm has also been observed in some other species (e.g., in genus Dendrocalamus, Gigantochloa, Melocalamus, Schizostachyum) under cultivation at Bambusetum Baan Sammi: BS-0006, BS-0078, BS-0208, BS-0494, BS-0550, BS-0724. The diameter differences can be seen with the naked eye, but are not as impressive as in BS-0550.

  • Provisional identification: Gigantochloa sp.

  • Comments:

  • (1) Tentatively assigned to the genus Gigantochloa mainly on the basis of culm-leaf characteristics, but most other characteristics can be found in Bambusa, too.

  • (2) The culm-leaf of BS-0602 is similar to Gigantochloa nigrociliata but is without horn-like extensions of the auricles, and has an asymmetrical sheath apex.

  • (3) The Thai name ไผ่ผาก (phai phak), under which the plant was obtained, was associated with Gigantochloa hasskarliana (T. Smitinand, Thai Plant Names, rev. ed., 2001: p. 252). Gigantochloa hasskarliana from Indonesia might be a species different from what has been described for plants in Thailand and Malaysia under the same species name. BS-0543 and BS-0542 have recently and provisionally been assigned to Gigantochloa hasskarliana, and the characteristics of BS-0543 and BS-0542 are indeed very similar to BS-0602, and they might represent the same species.

  • (4) The Thai name ไผ่ผาก (phai phak) is also associated with Gigantochloa densa in many Thai horticultural and forestry publications and on Thai Wikipedia. This species was briefly described (Kew GrassBase), as having hairy leaf blades 5–12 cm long and 1 cm wide, whereas in BS-0602 leaf blades are glabrous on both surfaces and notably larger both in length and width; therefore, it can certainly be excluded that BS-0602 represents Gigantochloa densa.

  • (5) The Thai name ไผ่ผาก (phai phak) is also associated with Gigantochloa auriculata sensu Gamble non Kurz (S. Sungkaew & al., ไผ่ในเมืองไทย (Bamboo of Thailand), 2011: p. 162-163, 5 photos). Judging from the illustrations in Gamble's and S. Sungkaew's publications, habit, shoots, and culm-leaves are substantially different; therefore, it can definitely be excluded that BS-0602 represents Gigantochloa auriculata.