Gigantochloa holttumiana

Type: Holotype KEP.

Thai name: ไผ่ไอยรา (phai aira) /'pʰàj ʔaj 'raː/.

Distribution: THAILAND: introduced from Malaysia and Singapore, cultivated, rare. — MALAYSIA (Peninsular): Pahang: Fraser Hill, wild.

Descriptions:

(1) "Culm sheaths pale green, orange-flushed at the top, densely covered with dark brown hairs; blade broadly lanceolate, spreading to reflexed; auricles low rims 0.5–1 mm high with raised ends 1.5–2,5 mm high, glabrous but with occasional scattered bristles at the ends; ligule with an entire 1.5–2 mm base bearing long bristles 10–25 mm long. Culms to 10–15 m tall, commonly 3–5.5 cm diameter; internodes 50–60 cm long, dark green, occasionally streaked with paler green or yellow at the basal part of the culm, without white wax, with fine white hairs mixed with coarse appressed pale brown hairs near the top of the internode, often quite glabrous in older culms. Leaf: blades 15–30 cm long, 2.5–3.5 cm wide, pale hairy below; stalk 2–4 mm long; auricles small lobes 1–2 mm high, with golden brown spreading bristles; ligule a low inconspicuous rim 0.5–1 mm high with fine brown bristles 4–8 mm long. … [flowers described]." — K. M. Wong, Bamboos of Peninsular Malaysia, 1995: p. 126 [#1210].

(2) "Habit: Perennial; caespitose. Rhizomes short; pachymorph. Culms erect; 1000-1500 cm long; 30-55 mm diam.; woody. Culm-internodes terete; thin-walled; 50-60 cm long; mid-green; distally pubescent. Lateral branches dendroid. Buds or branches absent from lower quarter of culm. Branch complement several; with 1 branch dominant. Culm-sheaths auriculate; with 0.5-2.5 mm high auricles; ciliate on shoulders. Culm-sheath ligule 10-25 mm high; dentate. Culm-sheath blade lanceolate; spreading, or reflexed. Leaf-sheaths pubescent; hairs tawny. Leaf-sheath oral hairs ciliate; 5-12 mm long; dark. Leaf-sheath auricles erect; 1.5 mm long. Ligule a ciliate membrane; 4-8 mm long. Collar with external ligule. Leaf-blade base with a brief petiole-like connection to sheath. Leaf-blades lanceolate; 15-30 cm long; 25-35 mm wide. Leaf-blade surface pubescent; hairy abaxially. … [flowers and seeds described]." — KewScience POWO, accessed 10 July 2020 [#1305].

Images: Line drawing in K. M. Wong, l.c., 1995: p. 127-128 (fig. 66-67) [#1210].

Comments: Gigantochloa holttumiana is confined to Peninsular Malaysia, and a natural occurrence of this species in Thailand is not known (Mu Chakkrapong, pers. comm., Facebook, 17 Mar. 2020).

Characteristics (from a plant that has not yet reached its utmost height): Habit unicaespitose, a tight clump. Rhizome pachymorph. Culms straight, erect, slightly bending outwards above, over 5 m tall [ultimate height possibly over 10 m]. Young shoots conical, sheaths green with stripes, glabrous, culm-leaf blades spreading; emerge from March. Culm-internodes terete, 40–55 cm long, green with light to whitish green or yellowish green stripes, densely covered with short soft white hairs on young internodes (up to 2 or 3 years old), thus internodes appearing bluish, the lower part of the internode when young with denser, longer tomentose light brown hairs; diameter 2.5 cm [ultimate diameter possibly 4 cm or over]; walls moderately thick. Culm-nodes not prominent; nodal line horizontal, marginally protruding; supranodal line discernible, without a ridge, 10 mm above the nodal line; nodal line somewhat hairy, densely hairy below, glabrous above, but with a white sericeous ring between the sheath scar and the supranodal line, the sericeous hairs easily removable; aerial roots none. Branch-buds solitary, subrotund, pointed, present from the basal node up. Branches few to several, unequal, the central one dominant; unbranched on the basal and lower culm; branching intravaginal; rebranching. Culm-leaves deciduous, often loosely attached to the sheath scar before dropping, the basal culm-leaves often persistent, promptly deciduous on the branched nodes of the mid-culm and upper culm. Culm-leaf sheaths dome-shaped, about 12 cm wide at the base, 16 cm long, length usually less than 1-third of the internode; rigid and brittle when dry, often longitudinally torn in the middle over half the sheath length while still attached to the culm, green with light to whitish green stripes when young, light straw-colored when dry, scattered with appressed long brown hairs (initially light brown, becoming dark brown to almost black), denser and villose towards the base; apex slightly concave-rounded; the outer overlapping margin initially long brown ciliate, the inner margin short white ciliate, or almost eciliate. Culm-leaf auricles very low rims, ca. 1 mm high, adnate to and contiguous with the basal margins of the blade, the rims raising their height to about 4 mm into irregular, almost ovate erect or slightly outward-bent dark brown lobes towards the ends at the sheath margins, the low middle part of the rims entire (without fringes or bristles), the raised outer auricles with 1–1.5 (2) cm stiff rigid erect initially white (brown with age) persistent fringes terminating in stiff bristles. Culm-leaf ligule about 3–4 mm high, brown, with 1–1.5 (2) cm stiff rigid erect initially white (brown with age) persistent fringes terminating in stiff bristles. Culm-leaf blades rigid when dry, caducous, deflexed to horizontally patent, short triangular or long-pointed lanceolate on the lower culm, relatively short on the basal and lower culm, near the base ca. 1.3 cm wide, 5 cm long; adaxially almost glabrous, abaxially glabrous; green when young, light straw-colored when dry; margins eciliate, somewhat incurved. Foliage-leaves (9) 11 (13) per branchlet. Foliage-leaf sheaths keeled, green when young, light straw-colored when dry, initially whitish hirsute, becoming brown hirsute with age, margins eciliate. Foliage-leaf auricle an inconspicuous rim, ca. 0.5 mm high, adnate to and contiguous with the basal margin of the blade, the rim raising its height to an almost ovate tiny lobe towards the ends at the sheath margins, the lobes with a few more or less persistent relatively thick whitish bristles. Foliage-leaf ligule inconspicuous, margin entire; outer ligule an inconspicuous low rim. Foliage-leaf blades thick, ovate-lanceolate, (28) 35–40 (45) × (2.5) 4–5 (7) cm, glabrous and mid-green above, green to bluish-green and pubescent beneath; base rounded to wedge-shaped; apex attenuate; margins antrorsely scabrous; midvein proximally prominent, green to light green beneath; pseudopetiole 4–6 mm long, glabrous.

Uses: Not recorded; plants suitable for landscaping.

Cultivation requirements: Easy but slowly growing; in part shade to full sun, prefers moisture-retentive soil.

Comments:

(1) The characteristics of BS-0302 largely match those of Gigantochloa holttumiana, in particular, the culm-leaves including the auricles, ligule, and blade, match remarkably well.

(2) Photos of a bamboo, published as "Gigantochloa sp. 'Iyara'" by Boonthammee Bamboo Garden on Facebook, 4 Dec. 2020, shows Gigantochloa holttumiana. The plant at Boonthammee Bamboo Garden with the Thai name ไผ่ไอยรา (phai aira) /'pʰàj ʔaj 'raː/ was grown as an offset from one of the specimens BS-0302 or BS-0478 at Bambusetum Baan Sammi.

Characteristics: Habit caespitose, tight clump. Rhizome pachymorph, short. Culms straight, erect below, slightly bending outward above, 5 m tall [ultimate height not yet known, assumed to grow to 10 m tall]. Young shoots conical, green, hairy, culm-leaf blades spreading; emerge from June. Culm-internodes terete, 30–40 cm long, green, scattered with pale to brown hairs, proximally glabrous and distally scaberulose when old, occasionally with a few narrow light green stripes on the basal culm; diameter 2.5 cm [ultimate diameter not yet known]; walls moderately thick. Culm-nodes brown hairy when young, glabrous when old, flat; nodal line horizontal; sheath scar not protruding, 1–3 mm high; supranodal line discernible, without or with a slight ridge, 7–11 mm above the nodal line; with a narrow, faintly farinose band below the nodal line when young, the band ca. 5–7 mm high; aerial roots none. Branch-buds solitary, subrotund, slightly broader than tall, from the basal node up. Branches several, unequal, the central one dominant; unbranched on the basal and lower culm; branching intravaginal; rebranching. Culm-leaves deciduous on branched nodes of the mid and upper culm, late deciduous or persistent on the lower culm, and decaying while still attached to the internode on the basal culm. Culm-leaf sheaths parabolic, ca. 10–11 cm wide near the base, ca. 20 cm long, about half the length of the internode, papery, initially somewhat rigid, green when young, straw-colored when dry, darker when old, covered with appressed long pale to brown hairs; sheath apex rounded to truncate; margins pale to brown ciliate. Culm-leaf auricles adnate to the basal margins of the blade as very low and short rims ca. 0.5–1 mm high and 2 mm wide, extending into conspicuous, slightly unequally shaped lobes ca. 4–6 mm high and 6–10 mm wide at the ends, blackish, the rim glabrous and entire, the lobe glabrous, erect to aslant, with pale bristles to 15 mm long. Culm-leaf ligule 1–2 mm high, blackish, denticulate, with 10–20 mm long, erect pale persistent bristles. Culm-leaf blades papery to leathery, horizontally patent, reflexed when dry, caducous, but auricles remain persistent on the sheath apex; lanceolate, near the base 2 cm wide, the base constricted to 6 mm at the junction with the sheath apex, length ca. 6–15 cm on the lower culm; adaxially with a short small tuft of hairs at the base, abaxially glabrous or initially puberulent; green when young, straw-colored when dry; base rounded; apex long pointed; margins scaberulous, incurved when dry. Foliage-leaves ca. 6–10 per branchlet. Foliage-leaf sheaths green to light green when young, straw-colored when dry, pale hirsute; apex truncate; margins pale ciliate. Foliage-leaf auricles small, glabrous, green, convex-rounded rims; oral setae few, short, pale, caducous. Foliage-leaf ligule convex-rounded, ca. 1–1.5 mm high in the middle, brownish; margin with caducous pale ciliae; outer ligule an inconspicuous callus. Foliage-leaf blades, rigid, lanceolate to oblanceolate, 24–30 × 2.5–5 cm, glabrous above, initially puberulent beneath, becoming glabrous soon, dull green; base rounded to wedge-shaped; apex attenuate; margins antrorsely scabrous; midvein proximally prominent and light green beneath; pseudopetiole 2–3 mm long. Flowers and seeds are unknown.

Comments: The characteristics of BS-0478 are largely similar to those of BS-0302.