Gigantochloa sp. (TH: Phetchabun) 1

Characteristics: Habit tight caespitose. Rhizome pachymorph, short [n.v.]. Culms erect, straight, over 12 m long [ultimate size currently not known], apically arching. Young shoots green, with scattered dark hairy patches, with culm-leaf blades patent, emerge from June to October. Culm-internodes terete, 30–40 cm long, initially green and with very short, soft, caducous pale hairs, becoming glabrous, slightly rough and dull, not glossy, deep black toward the end of the growth period, not farinose; diameter 6.0 cm [ultimate size currently not known]; thick-walled, solid or nearly so on the basal culm, walls 1.5 cm by 5.6 cm in diameter at 2.9 m above the ground. Culm-nodes glabrous, smooth, not prominent, green when young, blackish green when old; supranodal line clearly discernible; aerial roots none; nodes on branches somewhat prominent. Branch-buds solitary, from the basal node up. Branches on the lower culm none, with the bud remaining dormant but very short and very thin side branches may occasionally develop; the mid-culm often with 1 thick long branch, to 5 m long; the upper culm with few to many thin subequal branches, often 1–3 slightly dominant and longer; branching intravaginal, rebranching. Culm-leaves early deciduous. Culm-leaf sheaths 22 cm wide at the base, 25 cm long, rigid, coriaceous, green when young, straw-colored when dry, covered with appressed short black hairs, except near margins and apex, the hairs denser toward the sheath base; margins eciliate; apex slightly concave truncate, 6–7 cm wide. Culm-leaf auricles rim-like, long, 2 mm high, the rim margin eciliate, ending less high and rounded before but close to the sheath margin, greenish-orange when young, becoming blackish soon. Culm-leaf ligule very high, up to 5 cm, blackish when young, straw-colored when dry, papery, margin irregularly shaped, notched, initially lacerate with a few whitish bristles, later eciliate, recurved and deeply cleft when old, crumbling in part when old. Culm-leaf blades coriaceous, caducous, strongly reflexed (on the mid-culm), lanceolate, 2–2.5 cm wide at the junction with the sheath apex, about one-third of the sheath apex width, 18 × 4 cm, shorter than the sheath on the lower culm, usually 1/2–1/3 of the sheath length, as long as or longer than the sheath on the mid-culm and upper culm, green with purplish tint when young, soon becoming dry and straw-colored, adaxially densely hairy near the junction with the sheath, abaxially glabrous. Foliage-leaves 8–10 per branchlet. Foliage-leaf sheaths green, sparsely pale hispid; apex reddish when young. Foliage-leaf auricles inconspicuous or none, without bristles. Foliage-leaf ligule low, entire, eciliate. Foliage-leaf blades thin, medium-sized to small, 12–25 × 1.2–2 (3) cm, linear-lanceolate, mid-green, glabrous above, finely pubescent beneath when young, becoming glabrous soon; base rounded to wedge-shaped; apex attenuate; margins antrorsely scabrous; midrib not prominent; pseudopetiole 1–2 mm long. Flowers and seeds are unknown.

Uses: Not recorded. Can be planted as a feature bamboo in gardens and for landscaping.

Cultivation requirements: Grows best in light shade, soil can be heavy loam, normal moisture-retentive to moist with good drainage.

Provisional identification: The species is tentatively assigned to Gigantochloa for its rim-like culm sheath auricles.

Comments: The general appearance of this species, mainly its habit and small leaves, is similar to Phai Liang, ×Thyrsocalamus liang, but they are certainly not conspecific.