Gigantochloa sp. (TH: Songkhla: Khao Daeng)
Gigantochloa sp.
Thai name: No known records.
Distribution: THAILAND (South): Songkhla Province.
Culm size: Ultimate size not recorded, height over 8 m, diameter over 3 cm.
Uses: Not recorded. The species has ornamental value and can be used for gardens and landscaping.
Cultivation requirements: Easy-growing; in part shade to full sun, on heavy soil, moisture-retentive to moist with good drainage.
Specimen: BS-0582 [C1] = CS-3059B (living plants), น้ำตกเขาแดง, Khao Daeng Waterfall, 98 m altitude, อำเภอ สะบ้าย้อย, Saba Yoi District, Songkhla, southern Thailand, coll. C. S., 31 May 2010, received June 2010.
Gigantochloa sp. (BS-0582), from left to right (1–4): (1) Culm-leaf in a young stage: sheath pinkish, without scattered blackish hairs (but such hairs may occur on other culm-leaves of the same plant), and the stiffly erect, triangle-shaped blade dark. (2) Culm-leaf of mid-culm at a young stage: the green fresh culm-leaf blade is manually bent down from the sheath apex, showing a fully developed brown ligule with brown fringes terminating into white bristles; the oval-shaped blackish auricle is entire, without bristles. (3) A section of the mid-culm at an early stage of development: The culm-leaf blade has been manually removed from the triangular-shaped sheath apex, revealing the ligule as a brown band at an early stage of development that has not yet formed into fringes and bristles. (4) A section of a basal culm at a much-advanced stage of development: The dried white culm-leaf blade is manually bent down from the sheath apex, showing a fully developed, dried band of ligule with short fringes terminating into short bristles (on the mid-culm and upper culm, fringes and bristles would be conspicuously longer).
Characteristics: Habit tight caespitose. Rhizome pachymorph, short-necked [n.v.]. Culms straight, over 8 m tall [ultimate length not yet known], stiffly erect, slightly bending above. Young shoots green, glabrous, with erect culm-leaf blades; emerge from July/August (or earlier?). Culm-internodes terete, 27–33 cm long, green, without streaks, smooth, glabrous, but occasionally scattered with a few short black appressed hairs just below nodes with the surface becoming rough later; not farinose; diameter 3.5 cm [ultimate diameter not yet known]; thick-walled. Culm-nodes flat, glabrous, smooth; sheath scar not prominent, occasionally with a narrow white farinose ring below the sheath scar, fading early; supranodal line obscure but discernible, with or without a slight ridge; aerial roots none. Branch-buds solitary, from the basal node up. Branches initially 3, the central one dominant, long; unbranched on the basal and lower culm; branching intravaginal, all branches rebranching. Culm-leaves deciduous on branched nodes, persistent on the basal and lower unbranched nodes, and decaying on the culm. Culm-leaf sheaths 11–13 cm wide at the base, 14–20 cm long, slightly longer than half the length of the internode, thickly papery, greenish to pale pinkish when young, white to pale straw-colored when dry, occasionally scattered with short black appressed hairs, otherwise glabrous and smooth; margins short black ciliate when young; apex asymmetrical, triangular-truncate (from about the 4th basal sheath up, the apex of the lower sheaths is horizontally truncate or convex) with slightly raised edges, the triangular middle part about 2.5–3.5 cm wide and connected with the blade, each edge 1.5–2 cm wide and bearing the auricles. Culm-leaf auricles conspicuous, oval-shaped, 1–1.5 cm wide, 0.4–0.8 cm high, blackish when young, entire, without bristles. Culm-leaf ligule rather wide, extending at the sheath apex from edge to edge, width 5 cm and more, 2–4 mm high, somewhat higher towards the edges, fringed, ligule and fringes brown when young, fringes extending into fine several mm long white caducous bristles. Culm-leaf blades papery, persistent or late caducous, stiffly erect, long-triangular, apex long-acuminate, about half to three-quarters as long as the sheath length, dark brown when young, white to pale straw-colored when dry. Foliage-leaves (6–) 8 (–10) per branchlet. Foliage-leaf sheaths keeled, green, smooth, glabrous or nearly so. Foliage-leaf auricles of variable size, 2 mm long or smaller, rounded, entire, eciliate. Foliage-leaf ligule conspicuous, 6–10 (15) mm long, entire, pointed, pale brownish green when young, becoming lacerate when dry. Foliage-leaf blades large, 30–40 (56) × 2.5–5 (8) cm, linear-lanceolate, green, glabrous on both surfaces; base rounded to wedge-shaped; apex attenuate; margins antrorsely scabrous; midrib proximally prominent on both surfaces, light green beneath; pseudopetiole 2–3 mm long. Flowers and seeds are unknown.
Provisional identification: Similar to Gigantochloa ligulata, but internodes are glabrous, ligules are shorter, culm-leaf blades are long-triangular, and foliage-leaf blades are glabrous beneath.
Gigantochloa sp. (BS-0582): Upper abaxial section of an old culm-leaf taken from the mid-culm, showing the asymmetrical shape of the sheath apex, its triangular middle part and raised edges, the edges with rudiments of oval auricles, rudiments of the fringes of the ligule protruding the auricles, and the triangular spear-shaped blade.