Gigantochloa densa

Gigantochloa densa (BS-0046), from left to right: (1) Habit, showing a single significantly dominant and elongated branch on several culms; (2) culm-leaf on lower culm, its blade dropped off, showing a ligule much lower than in Gigantochloa albociliata, slender rudimentary branches, branching both extravaginal and intravaginal; (3) culm-leaf apex with dark green rim-like auricles, low ligule somewhat raised in the middle, and a reflexed blade brown hairy at the base; (4) lower part of a culm-leaf, showing a single patch of dense dark brown hairs near its base; (5) foliage-leaf blades showing their rounded bases with lobe-like edges.

• • Characteristics: Habit tight caespitose. Rhizome pachymorph, short-necked [n.v.]. Culms hard and durable, straight, erect or inclined, bending above and arching over to the ground, height 8 m [ultimate height much taller but not known]. Young shoots green to light yellowish straw-colored, conical, culm-leaf blades dark green, the uppermost erect, the lower ones reflexed; emerge from May/June/July. Culm-internodes terete, 32–37 cm long, sometimes not strictly straight but very slightly bent, dull green, with narrow yellowish green or light green stripes on lower culm, scattered with very short pale caducous hairs when young, denser below nodes, scabrous when old, not farinose; diameter 3 cm [ultimate diameter not known], thick-walled, solid or nearly so on the basal culm. Culm-nodes glabrous, smooth, not or slightly prominent; nodal line horizontal but slightly dipping below the bud; sheath scar marginally protruding 0.5–1 mm; supranodal line obscure, without a ridge, 8–15 mm above the nodal line; with a narrow whitish farinose ring below the nodal line when young, fading soon; aerial roots present on the basal nodes. Branch-buds solitary, subrotund, about 10 mm wide and 11 mm high, present from the basal node up. Branches several to many, with a single thick much dominant branch on some nodes from the mid-culm up, 1/2–3/4 as thick as the main axis, ascending and much elongated, bending, often not straight; a second subdominant branch may occasionally develop; additional short slender branches develop from nearly every node, usually 0.3–3 mm in diameter, on the lower culm as rudimentary branches with tiny leaf blades 3–10 × 0.5–1.6 cm; branching intravaginal and extravaginal, may occur simultaneously on the lower culm, branching intravaginal on the mid-culm and upper culm; rebranching. Culm-leaves persistent and decaying on the basal and lower culm, deciduous on the mid-culm and upper culm. Culm-leaf sheaths 12–15 cm wide at the base, 10–12 cm long, about 1/4–1/3 as long as the internode, rigid, brittle; light yellowish straw-colored, almost glossy, almost glabrous in the middle part and smooth when young, dull straw-colored to brownish when dry, abaxially scattered with caducous short soft light to dark brownish hairs along both sides when young; near base thickly covered with lasting dark brown velvety hairs, becoming black with age; margin eciliate; apex slightly convex truncate to obtuse-triangular truncate, symmetrical, about 6 cm wide. Culm-leaf auricles wide and low rims of consistent height, about 1 mm, adnate to the basal margins of the blade and extend along the sheath apex to the sheath margins, glossy dark green when young, changing to dark brown, entire, glabrous, without bristles. Culm-leaf ligule 3–4 mm high, convex-raised in the middle, denticulate or subentire. Culm-leaf blades persistent, occasionally caducous, papery, dark green when young, light straw-colored when dry, initially erect to spreading, becoming patent and reflexed with age; broadly lanceolate, about half as long as a sheath on the lower culm; junction with the sheath about 1.5 cm wide, adaxially thickly soft brown hairy near the base, otherwise glabrous; margins incurved with age; apex long pointed. Foliage-leaves 8–10 (11) per branchlet. Foliage-leaf sheaths keeled, green when young, initially pale hispid becoming glabrous and smooth with age; margins eciliate. Foliage-leaf auricles inconspicuous low rims, yellowish-orange when young, glabrous, without bristles. Foliage-leaf ligule 2 mm high, yellowish-orange when young, margin irregularly shaped, entire; ligule present. Foliage-leaf blades medium-sized, 12–32 × 3–4.5 cm, lanceolate, mid to dark green, glabrous above, puberulous beneath; base rounded with lobe-like edges, or rounded to cuneate, occasionally oblique; apex attenuate, often somewhat bent; margins antrorsely scabrous; midrib proximally slightly prominent; pseudopetiole 3–7 mm. 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.

  • Comments:

  • (1) The description (e.g., in Kew GrassBase) of the vegetative characteristics of Gigantochloa densa is rather sparse. Probably, as so often in the first descriptions of a bamboo species based on flowering material, the vegetative parts of the plant were not available or limited. The current identification of a living plant as Gigantochloa densa, based only on vegetative characteristics, is therefore not possible with sufficient certainty from the original description. Secondary collections are needed, living plants or herbarium material that represent this species by vegetative and generative characteristics. Such secondary material could be used in the identification of BS-0046, thanks to จ. ร. (pers. comm., Facebook, 23 Jan. 2018, and 15 Sep. 2019).

  • (2) Gigantochloa densa and Gigantochloa albociliata share some similar characteristics in branching type and culm-leaf. Both species seem to have the same branching type: a much more dominant and elongated branch may arise on nodes from the mid-culm up. However, the numerous short and very slender branches that arise from virtually every node in Gigantochloa densa do not seem to occur likewise in Gigantochloa albociliata. Very similar, too, are the shape, texture, and indument of the culm-leaves of Gigantochloa densa and Gigantochloa albociliata, but the latter has a much taller ligule. Another difference is the shape of the lanceolate foliage-leaf blades: The base of the blades is rounded with lobe-like edges in Gigantochloa densa, whereas usually cuneate and sometimes rounded in Gigantochloa albociliata.