Gigantochloa sp. (VN)

Specimen: BS-0500 [W3] (living plant), received as "Neohouzeaua mekongensis" from cultivated nursery stock (photo) in Queeensland, Australia, 7 June 2010, said to have been collected from the Mekong delta in Vietnam.

Characteristics: Habit tight caespitose. Rhizome pachymorph, short-necked. Culms to 15 m long, straight, stiffly erect, slightly bending above, tips occasionally drooping. Young shoots light green, conical; emerge from February to June. Culm-internodes terete, 30–50 cm long, internodes on the basal culm to about 2 m above the ground dull green to mid-green, scaberulous, initially densely covered with very short appressed blackish hairs (initially pale?), becoming glabrous with age, not farinose, higher internodes glabrous, almost glossy, bright mid-green; diameter to 5 cm; walls very thick to solid on the basal culm, thick-walled on the lower culm. Culm-nodes glabrous, flat; sheath scar protruding less than 1 mm; supranodal line discernible, without a ridge; with a narrow whitish farinose ring below the sheath scar when young; basal node occasionally with short aerial roots. Branch-buds solitary, triangular to subrotund, large, from the basal node up. Branches initially 3, the central one dominant and rather long, with 1–2 subdominant side branches, with additional slender branches on upper nodes; the lower culm up to about 3–5 m (the first ca. 13 nodes) unbranched or with a few very thin short rudimentary branches; branching intravaginal and extravaginal; rebranching. Culm-leaves on the lower culm usually persistent and decaying on the culm, on the upper culm usually late deciduous. Culm-leaf sheaths about 20 cm wide at the base, about 24 cm long from the base to the sheath apex, longer than half the length of the internode on the lower culm, half as long on the mid-culm, thickly papery, whitish-green when young, light straw-colored when dry, with large patches of short, rigid, appressed blackish hairs, these patches usually arranged in two irregular lengthwise streaks from the base to the top, not reaching the left and right margin, and with an almost hair-free area in the middle part between the two lengthwise streaks; margins black-ciliate 3 mm long; apex truncate, about 9 cm wide, symmetrical, with the middle part slightly convex-raised. Culm-leaf auricles rounded lobes, about 6–8 mm wide and 3–6 mm high, glabrous, without bristles, reddish-brown when young, dull brownish when dry. Culm-leaf ligule 2–3 mm evenly high, entire. Culm-leaf blades papery, glabrous, stiffly erect, broadly triangular, basally about 7.5 cm wide at the junction with the sheath; apex long-pointed, somewhat attenuate; about 18 cm long, almost as long as the sheath, perhaps as long as, or slightly longer than the sheath from the mid-culm up; light green or light orange when young, light straw-colored when dry. Foliage-leaves 6–8 (15) per branchlet. Foliage-leaf sheaths yellowish green when young, straw-colored when dry, glabrous, smooth; margins eciliate. Foliage-leaf auricles small rounded lobes, glabrous, without bristles, light orange-brown when young. Foliage-leaf ligule inconspicuous, less than 1 mm high, entire; outer ligule present, rim-like, low. Foliage-leaf blades moderately thick, green, medium-sized, (20) 35–40 (46) × (3) 4–5.5 (6.5) cm, lanceolate, glabrous on both surfaces; base rounded to wedge-shaped; apex attenuate; margins antrorsely scabrous; midrib proximally prominent on both surfaces, proximally yellowish-green beneath; pseudopetiole 4–7 mm long. Flowers and seeds are unknown.

Cultivation requirements: Easy-growing; in part shade to full sun, sandy loam to clay loam, normal moisture-retentive to moist with good drainage.

Provisional identification: Gigantochloa sp.; BS-0500 is most similar to Gigantochloa manggong, but they are certainly different species.

Comments:

(1) The specimen was received as Neohouzeaua mekongensis. However, Neohouzeaua mekongensis has thin culm walls, long-bristly auricles, and lanceolate, deflexed culm-leaf blades. Therefore, it can be ruled out that BS-0500 represents this species (now under Schizostachyum mekongensis).

(2) Photos of "Neohouzeaua mekongensis", which are not this species but most likely the same species as BS-0500: bamboocraft.net (habit, node, culm sheath) [#1341]; BambooWeb.info "from Vietnam" (culm, shoot, culm sheath, leaves) [#1340]; TropicalBamboo.org (habit).