Gigantochloa sp. (TH) 2

Gigantochloa sp. (BS-0598): Young culm-leaf, lower culms with an old culm-leaf, branch at mid-culm, habit (from left to right)

• • Characteristics: Habit caespitose, clumps erect below, bending and scrambling above. Rhizome pachymorph. Culms erect, unbranched on the lower culm (branched from about the 6th–9th node above the ground). Young shoots emerge from May/June. Culm-internodes 24–39 (44) cm long, dull green, rough, occasionally with a few narrow yellowish stripes on lower culm, scattered with very short pale fuzz when young, diameter 4.5 cm (in an immature and disturbed, 6-year-old plant), solid on the lower culm (at 1.6 m above the ground), moderately thick-walled to thin-walled and prone to splint on the upper culm. Culm-nodes slightly prominent; sheath scar glabrous, with remnants of decaying culm-leaf sheath when old; nodal ridge inconspicuous. Branch-buds large and prominent, ca. 3.2 cm wide, 2.3 cm tall, and 0.5 cm prominent. Branches on the basal and lower culm lacking, or with several very thin (diameter 0.2–3 mm) and short branches (with very small leaf blades), on the lower culm and mid-culm with a single very dominant branch, nearly as thick as the main culm, occasionally with additional very thin and short branches (as on the basal culm), and on the upper culm typically with 3 thin subequal (diameter 0.1–0.4 cm) short branches; branching extravaginal. Culm-leaves persistent, decaying on the culm. Culm-leaf sheaths leathery, brittle, about one-third as long as the internode, light green and with cream stripes when young, dark brownish when dry, with two narrow lengthwise patches of dense rigid short blackish hairs, otherwise glabrous or nearly so; margins eciliate; apex flat rounded. Culm-leaf auricles rim-like, broad and low, about 10 × 1 mm, entire, green or dark green when young; oral setae none. Culm-leaf ligule low, 1–2 mm, entire. Culm-leaf blade erect, broad triangular-lanceolate to broadly lanceolate, about 5 cm wide and 12 cm long on lower culm, light green to dark green when young, with cream stripes, attachment with sheath about 3 cm wide, apex acuminate, occasionally caducous. Foliage-leaves (4) 6 (8) per branchlet. Foliage-leaf sheath light green, initially hispid, becoming glabrous; margins eciliate. Foliage-leaf auricles small, rounded, entire; oral setae none. Foliage-leaf ligule short, entire. Foliage-leaf blades (14) 23–26 (39) × (1.9) 2.2–3.5 (3.7) cm on the mid-culm and upper culm, very small and often numerous (to 12 blades per branchlet) on the basal and lower culm, 2.5–8 (12) × 0.3–1.1 cm, glabrous on both surfaces, mid-green; margins antrorsely scabrous; base rounded to cuneate; apex acuminate and slightly twisted; midrib proximally prominent beneath, side veins more than 20; pseudopetiole 2–3 mm long, light green.

  • Provisional identification: Gigantochloa sp.

  • Comments:

  • (1) Tentatively assigned to the genus Gigantochloa mainly on the basis of culm-leaf characteristics. Branching is unusual and resembles Melocalamus.

  • (2) The Thai name ไผ่ผาก (phai phak), under which the plant was obtained, is associated with Gigantochloa hasskarliana (T. Smitinand, Thai Plant Names, rev. ed., 2001: p. 252). The descriptions of Gigantochloa hasskarliana do not match the characteristics of BS-0598.

  • (3) 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-0598 leaf blades are glabrous on both surfaces and notably larger both in length and width, therefore, it can be excluded that BS-0598 represents this species.

  • (4) 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 publication, habit, shoots, and culm-leaves are substantially different, therefore, it can be excluded that BS-0598 represents this species.