Dendrocalamus sp. (TH: N) — hok sop khong

Thai name: ไผ่หกสบโขง (phai hok sop khong).

English name: Sop Khong Bamboo.

Distribution: THAILAND (North): Chiang Mai Province: ต. สบโขง อ. อมก๋อย, Sop Khong Subdistrict, Omkoi District, wild, above 1,000 m altitude.

Culm size: Height up to 20 (25) m, diameter to 15 (20) cm.

Description: Not available.

Uses: Culms for construction; plants for landscaping.

Comments:

(1) Several plants of this species in Sop Khong Subdistrict flowered in the 2010s. Seedlings were collected by HRDI (Highland Research and Development Institute, สถาบันวิจัยและพัฒนาพื้นที่สูง) in 2018.

(2) The species could not be identified. The characteristics visible in the photos have been compared with Dendrocalamus hamiltonii, D. brandisii, D. longispathus, D. sp. (Phai Hok Wat Chan), and Gigantochloa macrostachya, but do not fit sufficiently with them.

Characteristics (based on photos of the plant and a leafy specimen provided by Thammarat Boonthammee): Habit unicaespitose, tight. Rhizome pachymorph, short. Culms straight, erect, slightly bending outward above. Young shoots conical, pale green, with spreading green culm-leaf blades. Culm-internodes terete, green, with narrow light green or yellowish green stripes of varying widths, scattered with short white hairs. Culm-nodes not prominent, with a narrow white densely fuzzy transverse band below the nodal line. Branch-buds solitary, ovate, broader than tall. Branches several, unequal, the central one dominant, 2 side branches subdominant, and a few slender branches; unbranched on the basal and lower culm; branching intravaginal; rebranching. Culm-leaves late deciduous. Culm-leaf sheaths parabolic, half as long as the internode or a little longer, pale green, with stripes in green and yellowish green when fresh, scattered with short white hairs when young; apex rounded; margins white ciliate. Culm-leaf auricles rim-like, low and long slightly raised and rounded toward the ends, dark brown when young, rim margins pale ciliate, the rims adnate to and contiguous with the basal margins of the blade, extending toward but not reaching the sheath margin. Culm-leaf ligule high, continuous with the apical sheath margin, dark brown when young, long pale ciliate. Culm-leaf blades deflexed to reflexed, lanceolate. Foliage-leaves ca. 10 per branchlet. Foliage-leaf sheaths green, with short pale hairs, becoming glabrous; apex truncate; margins pale ciliate or eciliate. Foliage-leaf auricles inconspicuous or none. Foliage-leaf ligule high, convex-rounded; margin pale ciliate. Foliage-leaf blades large, to ca. 41 cm long and 7 cm wide, lanceolate, mid to dark green, glabrous on both surfaces; margins antrorsely scabrous; base rounded to cuneate; midrib proximally prominent on both surfaces, yellowish green below; pseudopetiole to ca. 2 mm long. Flowers not seen.

Comments: Of all the cultured seedlings obtained, Mr. Thammarat observed after one year that a single seedling developed striped culms, whereas all the others had plain green culms. After a few years, this mutation turned out to be stable. Mr. Thammarat created the name 'Phai Sop Chok' (ไผ่สบโชค) for this cultivar.

References: Thammarat Boonthammee, on Facebook, 16 July 2022; Boonthammee Bamboo Garden, on Facebook, 16 July 2022; pers. comm. with Thammarat Boonthammee via email, 14–19 July 2022, pers. comm. 8 Aug. 2024.