Thyrsostachys siamensis

Type (lectotype): Thailand, Kurz s. n., K000290619, designated by C. M. A. Stapleton, Taxon 47 (3), 1998: 739-740.

Synonyms: Bambusa regia Thomson ex Munro, Trans. Linn. Soc. London 26 (1), 1868: 116, nom. rej.; Thyrso­stachys regia (Munro) Bennet, Indian Forester 114 (10), 1988: 711, nom. rej.

Thai names: ไผ่รวก (phai ruak) / 'pʰàj 'rûːak / (Central); ไผ่ฮวก (phai huak) (Northern); ตีโย (ti yo) (Central); ว่าบอบอ (wa-bo-bo), แวบ้าง (wae-bang), แวปั่ง (wae-pang) (Karen: Mae Hong Son); สะลอม (sa-lom) (Shan: Mae Hong Son). — T. Smitinand, 2001 [#1003]; BKF [#1368].

Indonesian names: bambu payung; bambu siam.

English names: Monastery Bamboo, Siamese Bamboo, Thai Bamboo, Umbrella Bamboo, Thai Umbrella Bamboo.

Distribution: THAILAND (North, West, Central) native, wild, cultivated throughout Thailand; in mixed deciduous forest and deciduous dipterocarp forest, 70–1,000 m altitude. — MYANMAR: wild and cultivated. — CHINA (South): Southern Yunnan, only cultivated, not native (王平元 pers. comm., WeChat 31 Oct., 2 Nov. 2020). — LAOS (Central). — VIETNAM. — MALAYSIA, cultivated. — INDONESIA: throughout, introduced. — Introduced and cultivated in many countries of tropical and subtropical Asia. — N. Bystriakova & al., Bamboo Biodiversity, 2003: map 46 [#1342].

Culm size: Height of max. 13 m, diameter of max. 6 cm.

Descriptions:

(1) "A very graceful, cæspitose deciduous bamboo. Culms 25 to 40 ft. [7.6–12.2 m] high, straight, not branching till high up, 1·5 to 3 [sic!] in. [3.8–7.6 cm] in diameter, usually covered with the persistent old culm-sheaths, otherwise greyish-green; nodes not prominent; internodes 8 to 11 in. [20–28 cm] long, with a white ring below the nodes. Culm-sheaths 9 to 11 in. [23–28 cm] long, 4·5 to 8 in. [11–20 cm] broad, soft, thin, covered with fine white appressed pubescence on the back, striate, attenuate upwards to a wavy truncate top, about 1·5 in. [3.8 cm] broad, produced at the margins into short triangular auricles; imperfect blade 4 to 5 in. [10–13 cm] long, narrowly triangular, the edges recurved; ligule narrow, ·1 in. [2.5 mm] broad, glabrous, finely ciliate. Leaves narrow, linear, 3 to 6 in. [7.6–15 cm] long, ·3 to ·5 in. [0.7–1.3 cm] broad, rounded or attenuate at the base into a very short (·05 in. [1.3 mm] long) petiole; points short, twisted; glabrous on both sides, or slightly pubescent beneath when young; scabrous on one edge; main vein narrow, secondary veins 3 to 5, intermediate 6 to 7; leaf-sheaths striate, white pubescent and ciliate, truncate, and ending in a glabrous callus; ligule very short, ciliate; branches after flowering often producing tufts of wiry branchlets, with very small leaves. [flowers described] … It is easily distinguished from T. Oliveri by its much smaller size in almost all respects. …" — J. S. Gamble, Bambuseae Brit. India, 1896: p. 59-60 [#1230].

(2) "Densely tufted, sympodial bamboo. Culm erect or with arching tips, 8–14 m tall, 2–7.5 cm in diameter, wall very thick, solid in lower part, smooth, greyish-green, usually covered with persistent old culm sheaths; internodes 15–30 cm long, bearing a white ring below the nodes; nodes not swollen. Branches arising from midculm nodes upwards, with many branches at each node of which the primary one dominant. Culm sheath 20–25 cm long, 10–20 cm wide near the base, narrowing up to 2.5 cm wide at the apex, persistent, pale to purplish-green turning stramineous and thin with age, covered with scattered, pale appressed hairs; blade narrowly lanceolate, 6–15 cm × 5–12 mm, erect, pubescent adaxially; ligule very short, shortly laciniate; auricles absent or very small. Young shoots pale to purplish-green. Leaf blade narrow, linear, 7–14 cm × 5–8 mm, pale green, usually glabrous; sheath striate, white hairy along the margins; ligule very short, entire; auricles absent or very short. Inflorescences borne terminally on leafy or leafless branches, consisting of a main branch and many thin branchlets bearing bracteate clusters of few pseudospikelets; spikelet about 17 mm long, comprising 1 empty glume, usually 2 perfect florets and a rachilla extension bearing a rudimentary floret. Caryopsis cylindrical, about 5 mm × 2.5 mm, surmounted by a yellowish, glabrous, soft, long beak." — S. Duriyaprapan & P. C. M. Jansen in S. Dransfield & E. A. Widjaja (eds.), Plant Resources of South-East Asia No. 7, Bamboos, 1995: p. 145-147, fig. [#1226].

(3) "Culms to 12 m, to 6 cm in diam.; internodes initially green, becoming gray-green, 20–30 cm; wall thick; nodes slightly thickened, with a white ring below. Branches several, main mid-culm ones to 1 cm in diam. Culm sheaths pale brown, 3/4–1 × as long as internodes, papery, appressed pubescent, margins ciliate, apex truncate; ciliate; auricles small; ligule ca. 1 mm; blade erect, base ca. 3/4 width of sheath apex. Leaf sheaths white pubescent and ciliate; ligule very short, pubes-cent; blade linear, 7.5–15 × 0.7–1.2 cm. Pseudospikelets 1.2–1.4 cm; prophylls to 0.8 cm; gemmiferous bracts 2 or 3; glumes 2 or 3; fertile florets 1–3. Fertile lemma 1–1.3 cm; palea slightly longer than lemma, narrow, bifid for 1/3 of its length; lodicules absent to 3. Anthers pale yellow, apex purple, apiculate. Ovary ovoid to turbinate; style 1, ca. 1.2 cm; stigmas 1–3. Caryopsis ca. 0.6 cm. 2n = 76*." — Flora of China [#1303].

(4) "Culms 5–15 m long, 1.5–6 cm in diameter, covered with appressed white hairs when young, becoming glabrous when mature; internodes initially green, becoming gray-green, 15–30 cm long; walls very thick to solid or nearly so, particularly from lower internodes; nodes slightly prominent, with a white waxy ring below. Culm leaves very persistent; 3/4–1 as long as internodes, chartaceous; culm-leaf sheaths 10–20 × 5–15 cm, apex somewhat truncate or rounded to convex, 2–3 cm wide, abaxially covered with appressed white to pale brown hairs; ligules 0.5–2.5 mm high, margin ciliolate; culm-leaf blades erect to slightly arched, deltoid to linear-lanceolate, 3.5–15 × 1–2 cm, base ca ½–⅔ width of the sheath apex, pubescent. Foliage leaves (3–)5–7 per branchlet; pseudo-petioles 0.05–0.15 cm long; foliage-leaf sheaths 2.5–3.5 cm long, abaxially hairy, margins ciliate; auricles absent, fimbriae and oral setae absent; ligules short, ca 0.5 mm high, margin ciliolate; foliage-leaf blades narrowly linear, 5–15 × 0.3–0.7 cm, adaxially scaberulous only on lateral veins near the margin and near the midrib or glabrous, abaxially hairy, base somewhat truncate to cuneate or acute, apex acuminate. Pseudospikelets 1.2–1.4 cm long; bracts subtending prophyllate bud 2 or 3; empty glumes (1–)2 or 3, 0.75–1.2 cm long, apex acute, margins entire or ciliolate towards the apex, chartaceous, 8–15-nerved, back hairy, especially near the base, or glabrous. Fertile florets 1–3; rachilla internodes between fertile florets 1–2 mm long, scantly hairy to glabrous; lemmas similar to the glumes, 1–1.4 cm long, apex acute, margins ciliolate towards the apex, 14–29-nerved, abaxially slightly pubescent only near the base and the tip, otherwise glabrous; paleas membranous to thinly chartaceous, hairy to glabrous abaxially, usually as long as or slightly shorter than the lemmas, apex usually bifid for ⅟₁₀–½ of its length, 2-keeled, keels ciliate, 2 or 3-nerved between keels and 0 or 1-nerved between each keel and the ciliate and involute margin; lodicules (2–)3, rarely absent; anthers ca 3.5 mm long, apices acute to mucronate, glabrous; ovaries usually glabrous, style ca 1 cm long, stigmas 1–3. Caryopses 0.5–0.8 cm long, glabrous." — S. Sungkaew & al., Thai For. Bull. (Bot.) 49(1), 2021: 53-54 [#1358].

(5) Kew GrassBase [#1335].

Characteristics (distinguishing vegetative characteristics between Thyrsostachys oliveri and Thyrso­stachys siamensis): See under → Thyrsostachys oliveri.

Images: Line drawing in Flora of China [#1303]; Flora of Taiwan [#1106]. Photos in AsianFlora (habit, culms) [#1332]; photo of the type of Bambusa regia at Kew Herbarium (culm sheath, leafy branch) [#1333]; photo in R. Pattanavibool in A. N. Rao & al. (eds.), 1998: fig. 9 (seeds) [#1211]; in S. Sungkaew & al., 2021: fig. 1D–F (apex of young shoot, flowering branches) [#1358].

Characteristics: Rhizomes pachy­morph, short-necked, forming a very tight clump. Young shoots emerging from early or mid-June to August/September. Culms stiffly erect on the lower and middle part, slightly bending above from the weight of foliage, unbranched on the lower part. Culm-internodes mid-green to dark-green, glabrous, glossy, or initially thinly covered with white fuzz, yellowish green to brown when old; thick-walled, basal internodes solid. Culm-nodes not prominent; sheath-scar ring black when young, soon fading to light gray. Branch-buds solitary. Branches several, subequal, with one branch slightly dominant; branching intravaginal. Culm-leaves of lower culm persistent, decaying while attached to the culm; upper culm-leaves (where branches develop) deciduous; lower culm-leaves longer than the internode, upper culm-leaves shorter. Culm-leaf sheaths green, lower ones reddish-green when young, soon drying to straw color, light gray or almost white color, covered with whitish fuzz when young, glabrous soon after; sheath apex convex-truncate. Culm-leaf auricles inconspicuous or none, bristles none. Culm-leaf ligule very short, convex, entire. Culm-leaf blade typically reflexed in the young culm, blade soon deciduous from the sheath on the lower culm. Foliage-leaves usually 8 per branchlet. Foliage-leaf auricles and bristles none. Foliage-leaf ligule inconspicuous. Foliage-leaf blades dark green, long and narrow, of varying sizes, the largest about 15 (18) cm long and 9 (11) mm wide, glabrous on both surfaces. — All characteristics are based on specimens cited below.

Uses: Shoots for food; culms for construction, furniture, fencing, handicrafts, and paper pulp; plants as ornamentals and for hedges, screening, and windbreaks. One of the most useful species.

Cultivation requirements: Easy-growing, thrives well in heavy (loamy, clay) moisture-retentive soil with good drainage, but can grow even in poor and dry soil. It prefers partial shade but grows well in full sun if the soil does not dry out, and it tolerates full shade, too, as well as flooding.

Flowering and seeding: Seeds of "ไผ่รวก" (phai ruak) by ลุงไทย ไผ่เชียงราย (Lung Thai Chiang Rai), on Facebook, 11 Apr. 2021, and 11 Apr. 2021. Flowering of "ไผ่รวกใหญ่ [phai ruak yai] Thrysostachys siamensis" recorded by Jeera Makmee, on Facebook, 20 Apr. 2021. Flowering of "ไผ่รวก" (phai ruak), T. siamensis, wild on "เขาตะเภา" (khao taphao), Taphao Mountain, in (ต. พะเนียด อ. โคกสำโรง จ. ลพบุรี) Lopburi Province, Central Thailand (photo of a flowering branch by Mu Chakkrapong, on Facebook, 20 Oct. 2021, and pers. comm., Facebook, 20 Oct. 2021).

Flowering cycle: 45–50 years.

Seed viability: 1–2 years under normal conditions, a little over 2 years at low temperatures and low moisture content.

Comments: The diameter of culms in the description by Gamble (1896): "… 1·5 to 3 in. [3.8–7.6 cm] in diameter …" This is certainly an error. If the growth height of Thyrso­stachys siamensis is less than that of Thyrso­stachys oliveri, as Gamble notes, the diameter of Thyrso­stachys siamensis can not be greater than that of Thyrso­stachys oliveri.

Specimens: BS-0054 [W4], BS-0054-1 [BBG] (living plants), seedlings received as "ไผ่สร้างไพร" (phai sang phrai) from the Royal Project, Huai Hong Khrai (ห้วยฮ่องไคร้) Study Center, A. Doi Saket, Chiang Mai Province, Nov. 2011, grown from seed collected from flowering wild plants in Petchabun (เพชรบูรณ์), north-eastern Central Thailand.

Characteristics: Culm diameter to 4.5 cm (4 Apr. 2021). Culm-leaf blades 7–15 (19) × 0.8–1.0 (1.5) cm.

Comments:

(1) Very similar to BS-0569, especially the very steep convex line of the junction of the blade base and sheath apex. The ultimate culm height and diameter are not yet known.

(2) When receiving the plants as "ไผ่สร้างไพร" (phai sang phrai), a name that is usually attributed to Phai Liang, ×Thyrsocalamus liang, it was said that mature plants look similar to Phai Liang, but would grow taller in culm height and bigger in diameter than Phai Liang. By June 2015, however, it became apparent that the culm-leaves looked more like a species of Thyrsostachys, and by July 2017, it became clear that the plants are certainly not ×Thyrsocalamus liang, but most likely Thyrsostachys siamensis (Sep. 2017, Aug. 2018).

Specimens: BS-0938 [-] (living plants), raised from seeds from Kanchanaburi, western Thailand, without precise locality; the seeds collected as "Thyrsostachys siamensis from Kanchanaburi" by ธ. บ. in 2018, seeds received from ธ. บ., 15 June 2019. BS-0938-1 [-] (living plant), raised from seeds (same source) by ธ. บ. in 2018, seedling received from ธ. บ., 25 Oct. 2019.

Characteristics: Foliage-leaf blades 7–14 (15.5) × 0.8–1.3 (1.6).

Seed weight: Not recorded.

Seed germination: 5 seeds placed on moistened tissue paper, 18 June 2019, atmospheric humidity >70%, coleoptiles emerged in the first two days after sowing, germination rate very high (4 seeds germinated) (test 190618).

Comments: Flowering specimens were not collected, but photos of the flowering plants were taken.

Thai names: ไผ่รวกหวาน (phai ruak wan), ไผ่รวกหน่อหวาน (phai ruak no wan); "no" = shoot, sprout; "wan" = sweet.

Distribution: Thailand, cultivated.

Culm size: Height 5 - 10 m, diameter ca. 3 - 4 cm.

Characteristics: Young shoots very tasty.

Images: Post and photos by สวนไผ่บงหวาน เพชรน้ำผึ้ง (suan phai bong wan, phet nam phueng), on Facebook, 29 Mar. 2014; post and photos by Niramit Sareerudt, on Facebook, 13 Feb. 2014; post and photos by ชมรมคนรักไผ่ แห่งประเทศไทย (Thai Bamboo Lovers' Club), on Facebook, 19 Jan. 2014.

Specimens: No specimens were collected.

Uses: Planted for shoot production; shoots are very tasteful and sweet and can even be eaten raw.

Thai name: ไผ่รวกเศรษฐี (phai ruak setthi); "setthi" = millionaire, rich, wealthy.

Distribution: Thailand, cultivated.

Culm size: Height not recorded, diameter ca. 4 cm.

Images: Post and photos by Nanbamboo น่านแบมบู, on Facebook, 6 Feb. 2014.

Distribution: Thailand, cultivated.

Characteristics: Culm-internodes dark green to blackish.

Images: Post and photos by Thoop Nakasen (Nanbamboo น่านแบมบู), on Facebook, 4 Dec. 2017.

Uses: Plants as garden ornamentals.

Comments:

(1) This clone was raised from seeds by Nanbamboo, Nan, northern Thailand, between 2010 and 2016.

(2) อรุณี (Aruni), or transcribed as "Arunee" to satisfy English spelling and pronunciation, is a Thai first name for a female person.

Thai name: ไผ่เปร็ง (phai preng) /'pʰàj 'preŋ /.

Distribution: THAILAND, in cultivation, not frequent.

Characteristics: Culms with shortened internodes. Internodes thick-walled, solid on the basal culm. Culm-leaves persistent, whitish.

Uses: Culms used for walking sticks (videos on Facebook: แขก คนแปลกหน้า, Facebook, 20 Aug. 2020, and 11 July 2020); interior design (photos on Facebook: Tum Bamboo Garden, Facebook, 5 Dec. 2020, and เรือนศาสตร์ตรา อยุธยา, Facebook, 21 Feb. 2016); tobacco pipes ("ชื่อไผ่ชนิดหนึ่ง ต้นเล็ก ชาวบ้านใช้ปล้องทำเป็นกล้องยาสูบ" acc. Royal Institute Dictionary, 1982).

Comments: The overall appearance of this bamboo indicates a species of Thyrsostachys, possibly T. siamensis.

References: (1) สวนไผ่นานาพันธุ์ สวน, Facebook, 8 Nov. 2020. — (2) สวนไผ่นานาพันธุ์ สวน, Facebook, 2 Oct. 2019. — (3) สวนไผ่นานาพันธุ์ สวน, Facebook, 1 Mar. 2019.