Gigantochloa rostrata
Gigantochloa rostrata K. M. Wong, Malaysian Forester 45 (3), 1982: 349.
Synonym: Gigantochloa maxima var. minor Holttum, Gard. Bull. Singapore, 16, 1958: 116.
Thai name: no known records.
Distribution: THAILAND (West): Tak Province; on hills, at about 1,000 m altitude. — MYANMAR. — MALAYSIA (Peninsular): Gunung Ray on Langkawi Island; Selangor, cultivated.
Descriptions:
(1) "Culm sheaths green, often with paler green striations, covered with dark brown hairs; blade broadly lanceolate, spreading to reflexed; auricles low rims 0.5–1.5 mm high, glabrous; ligule a subentire rim 1–1.5 mm long. Culms to 4–8 m tall, commonly 2.5–3.5 cm diameter; internodes 20–30 cm long, dark green, occasionally streaked with paler yellowish green at the basal part of the culm, without white wax, with scattered dark hairs all over. Leaf: blades 8–30 cm long, 1–3 cm wide, glabrous to pale short-hairy below; stalk 3–5 mm long; auricles inconspicuous rims hardly 0.5 mm high, glabrous; ligule a conspicuous subentire extension 3–8 mm long; on larger leaves the sheath developing a scale-like callus on the abaxial side near the top … [flowers described]." — K. M. Wong, Bamboos of Peninsular Malaysia, 1995: p. 134-137, fig. 75-76 [#1210].
(2) E. A. Widjaja, A Revision of Malesian Gigantochloa (Poaceae–Bambusoideae), in Reinwardtia, vol. 10(3), 1987: p. 333-335, fig. 15 [#1224].
(3) "Culms densely tufted, straight and erect, up to 12 m tall, 3—10 cm in diameter; internodes 30—50 cm long, green with pale to yellow stripes, non waxy, covered with appressed pale to dark brown hairs particularly on the top; walls about 0.8—1 cm thick at mid-culm portion. Branches developing on the upper part of the culm; mid-culm branch complements with several branches at each node arising from a single bud, the primary one dominant, 1—2 subdominant branches from its base and often several lesser branches. Culm leaves persistent, coriaceous, green with pale-yellow stripes, 21—32 cm long by 17—22 cm wide, top slightly concave, back covered by dark appressed short hairs, occasionally becoming glabrous; blades green to purple-green, slightly decurrent, lanceolate, spreading to reflexed, 8—13 cm long by 2—2.5 cm wide near the base, covered with densely dark brown hair on adaxial base; auricles dark purple to black, continuing from base of the culm-leaf blade, low rim-like, about 1—2 mm tall by 20 mm long, margins glabrous; ligule slightly denticulate, up to 3 mm high in the middle. Leaves 8—10 per branchlet; blades 13—17 cm long by 1.5—2 cm wide, lower surface glabrous to shortly pale-hairy below, bases acute to oblique-attenuate, pseudo-petiole 3—5 mm long; leaf sheaths 4.5—6.5 cm long, glabrous; auricles inconspicuous rim-like about 0.5 mm high, glabrous; scale-like callus present, one of them broadly triangular, shining, 1 mm high, margin slightly serrulate; ligule oblique, 3—5 mm high, margin sub-entire; secondary veins 7—9 pairs, intermediate veins 7. … [flowers described, seeds unknown]". — C. Rattamanee, Taxonomic Revision of Gigantochloa (Poaceae: Bambusoideae) in Thailand …, Thesis, Kasetsart Univ., 2014: p. 113-118, fig. 41-44 [#1225].
Specimen: BS-0676 [-] (living plant), on the roadside of National Road #1268 from อุตรดิตถ์ (Uttaradit) to พิษณุโลก (Phitsanulok), near อุทยานแห่งชาติภูสอยดาว (Phu Soi Dao National Park), northern Thailand, wild, abundant, coll. ศ. ส., 30 May 2011.
Gigantochloa rostrata (BS-0676): Young shoot (left), young culm, showing a striped internode, a striped culm-leaf sheath with scattered black hairs, a very long and low rim-like culm-leaf auricle, a prominent denticulate ligule with its height ascending towards the middle, and a reflexed blade with a dense patch of brown hairs just on the base of its adaxial surface (center), foliage-leaves, showing sheaths with long, oblique ligules (right)
Characteristics:
(1) Habit tight caespitose. Rhizome pachymorph, short [n.v.]. Culms erect, bending above [ultimate size not yet known, but expected to attain at least 10 m height by 8 cm in diameter]. Young shoots emerge February/March/April, blackish hairy on light green culm sheaths, sheath blades reflexed. Culm-internodes 25–38 cm long, scattered with short black appressed hairs on the upper one-third of the internode, otherwise glabrous and smooth, rough below nodes when old, with yellowish green to light green narrow stripes of varying width on the lower culm, uniformly mid-green on the mid-culm and upper culm; solid or nearly so on the basal culm, moderately thick-walled (wall 1/5 to 1/6 of the culm diameter) on the lower culm, thin-walled on the mid-culm and upper culm (wall 1/7 to 1/8 of the culm diameter), easily splintering. Culm-nodes glabrous, flat; sheath scar not or slightly protruding; supranodal line discernible, with a slight ridge, about 1 cm above the nodal line; aerial roots often present on the lower culm, short. Branch-buds solitary, from the basal node up. Branches initially 3, central one dominant, two side branches subdominant, and a few slender branches; branching extravaginal on the lower and mid-culm. Culm-leaves persistent on the lower and mid-culm, decaying on the culm, deciduous on the upper culm. Culm-leaf sheaths almost half as long as the internode, with whitish and light green streaks when young, scattered with patches of short appressed blackish hairs, hair density increasing from basal sheath to uppermost sheath, with the basal sheaths whitish as almost hairless, and the upper sheaths black throughout from very dense hair coverage; margins eciliate; apex somewhat rounded [as a flat Gaussian standard deviation curve σ ≈ 1]. Culm-leaf auricles inconspicuously low long rims, ca. 0.5 mm high, but ca. 1.0 mm towards the ends, erect, glabrous, eciliate, dark green when young. Culm-leaf ligule ca. 1 mm high, higher in the middle, ca. 3 mm, subentire, eciliate, dark green when young. Culm-leaf blade reflexed, adaxially thickly dark brown hairy at the connection to the sheath, otherwise glabrous, deciduous. Foliage-leaves 12–18 per branchlet. Foliage-leaf sheaths with a few short pale early deciduous hairs, otherwise glabrous, keeled. Foliage-leaf auricles an inconspicuous low rim. Foliage-leaf ligule 6–8 mm long, entire, reddish-brown when young. Foliage-leaf blades 28–32 cm × 3.3–3.8 cm, glabrous above, pubescent beneath; base unequally wedge-shaped; margins antrorsely scabrous; apex attenuate; midrib prominent; pseudopetiole short. Flowers and seeds are unknown.
(2) Culm wall 4 mm thick by 2.9 cm in diameter of the 13th internode about 3.5 m above the ground.
Uses: Not recorded. Suitable as garden ornamentals and for landscaping. Young shoots are not used for food locally.
Cultivation requirements: Easy growing; grows well in full sun, on sandy loam to clay loam, normal moisture-retentive to moist with good drainage. A nearly mature plant can withstand a short period of flooding but will suffer if the flood lasts longer than 7–10 days.
Provisional identification: Culm-leaf and other characteristics indicate a species of Gigantochloa. The characteristics of BS-0676 were compared with those of 18 Gigantochloa species from Thailand or adjacent countries. BS-0676 matches well only with Gigantochloa rostrata, but in BS-0676, the culm-leaf ligule seems to be higher, foliage-leaves are more numerous per branchlet, and leaf blades are longer and wider. Such variations could be within the range of the species.