Gigantochloa sp. (TH: S) 1

Thai name: ไผ่ด่างกาญจนา (phai dang kanchana), "dang" = spot, blotch, "kanchana" = gold (or is just a short expression for the name of the province of Kanchanaburi).

Distribution: THAILAND (South), possibly native, in cultivation: A nursery in Kanchana­buri distributed plants under the name "Arundinaria suberecta, ไผ่ด่างกาญจนา (phai dang kanchana)" for many years, and a nursery in Nan distributed plants as "Dangkarnjana" (Facebook, 18 Apr. 2016). The suspected origin of this species is southern Thailand. — U.S.A.: Cultivated plants are known from Florida as "Bambusa suberecta" hort., and as "Jesse Durko Bamboo"; the origin of these plants is unrecorded, but assumed to have been introduced from Thailand. — PHILIPPINES: In cultivation, plants were introduced from Thailand.

Uses: Plants are used as garden ornamentals and for landscaping.

Comments: There is currently no evidence that all the specimens cited hereunder are conspecific.

Specimen: BS-0635 [C9] (living plant), Trang, southern Thailand, cult., received from ธ. ล. as "ไผ่ฝากด่าง (phai fak dang)", 21 Mar. 2011.

Specimens: BS-0601 [BBG, SSG] (living plants), Thailand, without precise locality, plant with striped culms and leaves, from cultivation in Kanchanaburi Province, received as "ไผ่ลาย (phai lai)" from ธ. ล., 1 Dec. 2010, one plant started gregarious flowering in Apr. 2012, produced fertile seeds (→ BS-0601A) in Sep. 2012, and died in 2013.

Characteristics: The specimen BS-0601 went undescribed as the plant was at a young growth stage at the time of its introduction, and was transferred to Boonthammee Bamboo Garden soon after. However, a single plant raised from seeds (specimen BS-0601A) in 2012 is still in cultivation at Bambusetum Baan Sammi. It has since grown sufficiently tall for observation of its characteristics, and a detailed description was done on 3 Sep. 2023 (see below).

Seed viability: Unknown, viability is assumed to last at least a few months.

Seed weight: 0.3 g ≈ 6 dried spikelets (husk-wrapped seeds).

Seed germination: Seeds were collected from one cultivated, immature plant; a total of only about 30 seeds were collected, and about 20 seeds were sown out, of which only about 10 germinated. A single seed collected in Oct. 2012 was laid on moistened tissue paper, on 27 Oct. 2012, temperatures were not recorded, atmospheric humidity >70%, and the shoot emerged after 28(!) days. A further seed collected in Dec. 2012 was laid on moistened tissue paper, on 4 Dec. 2012, the shoot emerged after 64(!) days. Further seeds collected thereafter during the hot season in 2013 also resulted in rather late germination of more than one month and less than two months. From all the germinated seeds, a total of 5 seedlings survived. The flowering mother plant has beautifully striped leaves, whereas the seedlings, as expected, don't have stripes.

Flowering: A single, immature plant (BS-0601) started gregarious flowering in Apr. 2012 and died in mid-2013. Most spikelets turned out to be empty.

Comments:

(1) This is a species of the genus Gigantochloa, but the species has not yet been identified.

(2) BS-0601 and its descendant, BS-0601A [C2], are very similar to BS-0885, so I now (Sep. 2023) assume that they could well be conspecific. This similarity was revealed when BS-0601A grew taller with age. The current differences between these specimens may be confined to only two characteristics, but this may be only a temporary difference. BS-0885 has more than twice the culm height of BS-0601A, but the latter has been grown as a seedling and might not yet have reached its ultimate size in height and diameter. The other difference is that no bristles have been detected in the auricles of BS-0885, both the culm-leaf and foliage-leaf. Perhaps bristles may develop but are early caducous. In BS-0601A, it has been observed that bristles develop and are conspicuous, but they might occasionally not fully develop or drop off early.

Specimens: BS-0601A [C2] (living plant), raised from seeds of BS-0601 at Bambusetum Baan Sammi, a low quantity of seeds collected by D. O., from 20 Sep. 2012 to July 2013; from the only flowering plant, all seedlings developed green culms and leaves (without any variegation).

Characteristics: Habit unicaespitose, a dense clump. Rhizome pachymorph, short. Culms straight, erect, bending outwards above and arching, ca. 5 m long [ultimate size possibly somewhat longer]. Young shoots conical, yellowish green, scattered with appressed very short dark hairs; sheath margins eciliate; culm-leaf blades spreading, green; emerge from May to September. Culm-internodes terete, 23–33 cm long, mid-green to dark green, glabrous, almost glossy when young, proximally smooth, distally minutely pruinose; diameter (1.5) 2–3 cm; walls very thick, solid on the basal culm, wall width as wide as the lacuna diameter on the lower culm (e.g., culm diameter 2.4 cm, wall width 0.8 cm, lacuna diameter 0.8 cm); lacuna without pith. Culm-nodes glabrous, smooth, not or slightly prominent; nodal line horizontal, dipping slightly below the bud; sheath scar dull black when young, marginally protruding 0.5 mm, with a narrow, slightly farinose transverse band just below the sheath scar when young; supranodal line obscure or irrecognizable, without a ridge; aerial roots none. Branch-buds solitary, ovate, two times broader than tall, from the basal node up. Branches several, unequal, the central one dominant, with 2 side branches subdominant, and a few smaller branches, long, initially upright; branching from the mid-culm up, the basal and lower culm usually unbranched; branching intravaginal. Culm-leaves early or late deciduous. Culm-leaf sheaths parabolic, ca. 12 cm wide at the base, to about 22 cm long, about 2/3 as long as the internode on the lower culm, leathery, light green when young, straw-colored when dry, more or less scattered with appressed very short dark hairs; apex horizontally truncate, symmetrical; margins eciliate. Culm-leaf auricles rim-like, brownish to blackish when young, each auricle equal in shape and size, and adnate to and contiguous with the basal margin of the blade as a slightly bent rim of low height (ca. 1–1.5 mm), and extending to the sheath margin by constantly increasing its height to 3–4 mm, thus forming an upright or slightly outward-bent triangular or obovate lobe; the rim margin entire, without bristles, the lobe margin entire but with erect pale bristles to about 5 mm long. Culm-leaf ligule very low, 1–1.5 mm high, dull blackish when young; the margin denticulate, with a few to several erect, early caducous pale bristles up to about 2 mm long. Culm-leaf blades leathery, reflexed to strongly reflexed, persistent or late caducous, narrowly lanceolate or long narrowly triangular; the base 1.3 cm wide, constricted to 0.7 cm at the junction with the sheath apex; adaxially with appressed very short hairs near the base, abaxially glabrous; light green when young, straw-colored when dry; apex sharp-pointed; margins scabrous, distally incurved. Foliage-leaves 7–11 per branchlet. Foliage-leaf sheaths light green when young, scabrous or pale hirsute; margins eciliate. Foliage-leaf auricles are low rims, raised to lobes toward the ends, green, the margin of the ends with several slightly undulated erect pale bristles to ca. 8 mm long. Foliage-leaf ligule inconspicuous, low, ca. 0.5–1 mm high; margin subentire; outer ligule inconspicuous or none. Foliage-leaf blades soft, lanceolate, 13–23 (27) × 1.6–2.6 (3.2) cm, glabrous above, puberulent beneath, medium to dark green above, medium green to bluish-green beneath; base rounded to wedge-shaped; apex attenuate; margins antrorsely scabrous; midvein proximally prominent, light green beneath; pseudopetiole short, 1–2 mm long.