Thyrsostachys oliveri

Type: 9 specimens of J. W. Oliver, s.n., Upper Burma, 1891/1892 (K), none of them designated as the type. — KewScience POWO, accessed 6 Nov. 2020 [#1305]. — Lectotype: K000854869, designated by Kumari, 2019, and by S. Sungkaew & al., 2021: 51–53 [#1358] — Royal Botanic Gardens, Kew (2024). Royal Botanic Gardens, Kew - Herbarium Specimens. Occurrence dataset https://doi.org/10.15468/ly60bx accessed via GBIF.org on 2024-12-11. https://www.gbif.org/occurrence/912645963.

Thai names: ไผ่รวกดำ (phai ruak dam) / 'pʰàj 'rûːak 'dam /, ไผ่รวใหญ่ (phai ruak yai) (Northern); ว่าบอซู (wa-bo-su) (Karen: Mae Hong Son); สะหลอน (sa-lon) (Shan: Northern); เปา (pao) (Shan: Northern). — T. Smitinand, 2001 [#1003]; BKF [#1368].

Burmese name: "Thanawa"; Kachin name: "Maitong".

English name: Oliver Bamboo.

Distribution: THAILAND (North), native, wild and cultivated, also cultivated in other parts of Thailand; in mixed deciduous forest, 700–1,300 m altitude. — MYANMAR (North). — INDIA (North, North-East), cultivated. — LAOS. — CHINA (South): Southern Yunnan, only cultivated, not native (王平元 pers. comm., WeChat 31 Oct., 2 Nov. 2020). — Introduced and cultivated in several countries of tropical and subtropical Asia.

Local distribution: In Chiang Mai, this species is reported to grow wild in the Doi Suthep – Doi Pui National Park (not seen).

Culm size: Height 10–15 (25) m, diameter 5–8 cm.

Descriptions:

(1) "A large cæspitose bamboo with straight culms from a thick rootstock. Culms 50 to 80 ft. [15–24 m] high, 2 to 2·5 in. [5–6.4 cm] in diameter, bright green with whitish silky down when young, dull green or yellowish when old; nodes very little thickened; internodes 16 to 24 in. [40–61 cm] long, walls rather thin. Culm-sheaths somewhat thin, imbricating at the base, above three-fourth of the length of the internodes, green when young, then turning orange and finally brown, persistent, clothed on the back with thick white stiff pubescence, somewhat rounded at top, but then cut off to a breadth of 1 to 1·2 in. [2.5–3.0 cm], ciliate at the edges, not auricled, though slightly produced; imperfect blade long, recurved, subulate, acuminate, hairy above, 8 to 9 in. [20–23 cm] long by ·7 in. [1.8 cm] broad; ligule ·1 in. [2.5 mm] broad, serrate. Leaves light green, linear-lanceolate, acuminate; 7 to 8 in. [17–20 cm] long, ·5 to ·7 in. [1.3–1.8 cm] broad, rounded at the base into a short (·1 to ·2 in. [2.5–5 mm]) petiole; somewhat rough on both sides, hairy beneath, scabrous on the edges, those of young plants broader, more hairy below and bearing long, bulbous-based, strigose hairs above; main veins narrow, secondary veins 6 pairs, intermediate 5 to 7, no regular transverse veinlets, but frequent irregular pellucid dots instead; leaf-sheaths striate, hairy, keeled, ending in glabrous or hairy ciliate calluses and slightly produced at the mouth, ciliate at the edges; ligule short, truncate, pubescent. … [flowers and seeds described] … this species is readily recognized by the other [Thyrsostachys siamensis] by its larger size in all respects. …" — J. S. Gamble, Bambuseae Brit. India, 1896: p. 58–59 [#1230].

(2) "Culms 10–20(–25) m tall, 5–7.5 cm in diameter, covered with appressed white hairs when young, becoming glabrous when mature; internodes initially bright green, becoming dull green, 30–60 cm long; walls rather thick, particularly from lower internodes; nodes slightly prominent. Culm leaves relatively persistent, ca ¾ as long as the internodes, chartaceous; culm-leaf sheaths 20–35.5 × 10–25.5 cm, apex somewhat truncate or rounded to convex, 2–9 cm wide, back 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, 7.5–25 × 1.5–8 cm, base ca ½–⅔ width of the sheath apex, pubescent. Foliage leaves 5–7 per branchlet; pseudo-petioles 0.05–0.5 cm long; foliage-leaf sheaths 3–5.5 cm long, abaxially hairy to glabrous, margins ciliate; auricles absent, fimbriae and oral setae absent; ligules short, ca 0.5 mm high, margin ciliolate; foliage-leaf blades linear-lanceolate, (10–)12–22.5 × (0.7–)1–1.8 cm, adaxially scaberulous and hairy abaxially, to glabrous on both sides, base somewhat obliquely cuneate, apex acuminate. Pseudospikelets 1.5–2.5 cm long; bracts subtending prophyllate bud 2 or 3; empty glumes 1 or 2, rarely 3, 0.5–1.2 cm long, apex acute, margins entire or ciliolate towards the apex, chartaceous, 11–21-nerved, back pubescent to glabrous. Fertile florets 2–6(–7); rachilla internodes between fertile florets 1–3 mm long, scantly hairy to glabrous; lemmas similar to the glumes, 0.9–2.5 cm long, apex acute, margins ciliolate towards the apex, 9–29-nerved, abaxially slightly pubescent to glabrous; paleas membranous to thinly chartaceous, hairy abaxially, usually as long as or slightly shorter than the lemmas, apex obtuse to bifid for ¼–⅓ of its length, 2-keeled, keels ciliate, 5–7-nerved between keels and 2–4-nerved between each keel and the ciliate and involute margin; lodicules 2 or 3, conspicuous, membranaceous, ovate to lanceolate, 1–1.2 mm long, margin ciliate; anthers 5–6 mm long, apices acute to apiculate, glabrous; ovaries hairy to glabrous, style ca 1.5 cm long, stigmas 3. Caryopses ca 1 cm long, glabrous." — S. Sungkaew & al., Thai For. Bull. (Bot.) 49(1), 2021: 51 [#1358].

(3) Kew GrassBase [#1335].

(4) Flora of China [#1303].

Characteristics (distinguishing vegetative characteristics between Thyrsostachys oliveri and Thyrsostachys siamensis): Culm height usually taller and culm diameter usually thicker in Thyrsostachys oliveri compared to Thyrsostachys siamensis. Culm-internodes of young culms densely covered with whitish fuzz, dull olive green in Thyrsostachys oliveri, glabrous or initially thinly covered with white fuzz on the upper part, glossy mid-green to dark-green in Thyrsostachys siamensis. In culm-leaves of Thyrsostachys oliveri, the junction between the sheath and the blade is a convex arc with a usual arc height of about 2–10 mm, rarely horizontal (arc height = 0), and rarely up to 15 mm high. In culm-leaves of Thyrsostachys siamensis, the junction between the sheath and the blade is a steep convex arc with an arc height usually more than 15 mm, sometimes a few cm high.

Images: Line drawing in Flora of China. Photos in AsianFlora (culm, leaves) [#1332]; in S. Sungkaew & al., 2021: fig. 1A–C (apex of young shoot, flowering branches) [#1358].

Uses: Shoots for food (shoots emerge late); culms for construction, paper pulp, furniture, handicrafts; plants as ornamentals and for windbreaks.

Flowering cycle: 48–50 years [#1302]; 48 years [#1320]. Flowering events recorded from India: 1881, 1940, 1987–1988. The next flowering event could be in the 2030s.

Seed weight: ≈15,000–18,000 seeds/kg → ≈15–18 seeds/g [#1302].

Seed viability: 1–2 years if stored at low temperatures.

Comments 1 (on distinguishing vegetative characteristics between Thyrsostachys oliveri and Thyrsostachys siamensis):

(1) The key to differentiating between Thyrsostachys oliveri and Thyrsostachys siamensis (in S. Sungkaew & al., 2021: 51 [# 1358]) contains only one vegetative character, namely the size of the leaf blades: Foliage-leaf blades 10–22.5 × 0.7–1.8 cm → T. oliveri; 5–15 × 0.3–0.7 cm → T. siamensis. In addition to the difference in the size of the leaves, differences in the size of other parts of the two species are also described, for example, culm height, culm diameter, pseudospikelets, whereby T. oliveri has significantly larger characteristics. Gamble had already pointed out the size difference as a key distinguishing feature between the two species: "... this species [T. oliveri] is readily recognized by the other [T. siamensis] by its larger size in all respects." (J. S. Gamble, 1896: p. 59 [# 1230]). However, is it really that easy to identify species based on size differences? I have no doubt that the herbarium material in Kew, selected as the lectotype and isolectotypes, verifies the size difference. I also think it is likely that the size differences of the two species in their natural distribution areas largely correspond to the size differences described. But what about plants that are cultivated outside of their natural range? In addition, I do not think it is unrealistic to assume that both species, which are extremely useful to humans, have been selected over the past centuries, among other preferences selected by culm height. Furthermore, it is to be expected that the species will develop different culm sizes outside their natural range under different growth conditions (more favorable as well as less favorable growth conditions). The culm size and the leaf size, considered alone or together, would hardly provide sufficiently reliable distinguishing features between species in plants kept in culture.

(2) In addition to the culm and leaf size, the indument of the culm-internodes is occasionally mentioned as a distinguishing feature of the two species. The culms of Thyrsostachys oliveri have been described as "… with whitish silky down when young …" (J. S. Gamble, 1896: 58 [#1230]), and as "… covered with appressed white hairs when young …" (S. Sungkaew & al., 2021: 51 [#1358]). While Gamble's description of T. siamensis does not contain any information about the indument of the culms or culm-internodes, S. Sungkaew & al. describe the culms in the same way as T. oliveri: "… covered with appressed white hairs when young …" (S. Sungkaew & al., 2021: 54 [#1358]). In general, it may be questionable whether the indument is even suitable as a species-differentiator. However, there appear to be significant differences in the indument between the two species.

(3) A total of more than 50 specimens at Bambusetum Baan Sammi could be assigned to the genus Thyrsostachys, of which 16 were still kept as living plants in 2010 [as of August 2022, only seven living specimens remained for further observation at Bambusetum Baan Sammi]. All of these are listed here, and descriptions of the vegetative characteristics of several of them have been added. In addition, I was able to observe numerous representatives of this genus in rural and urban areas of Chiang Mai; most or even all of them were planted. An unequivocal assignment to one of the two species was and has not been possible for me. All of these specimens can be grouped as follows: 

(4) Group 1: The specimens are adult or nearly adult plants and reach culm heights that correspond to the heights of Thyrsostachys oliveri and/or T. siamensis. In contrast, the leaf sizes of all specimens consistently correspond to those of T. siamensis. In other words, specimens that can be assumed to be T. oliveri due to their tall height have only small leaf blades. The culm internodes are covered with whitish fuzz (which can easily be wiped off with a finger). These specimens are listed here under T. oliveri. They come from Thailand, and the flowers and seeds are not known.

(5) Group 2: These are two specimens of supposedly tall plants from Thailand that have flowered, but the flower was not available; only seeds were obtained. The plants grown from the seeds have not yet been large enough to make any statements about their characteristics. These two specimens are listed here under Thyrsostachys oliveri.

(6) Group 3: These are plants raised from seeds, but the plants have not yet been large enough to describe their characteristics in detail. The seeds were received from China under the most bizarre names and with dubious indications of origin or lack of origin. It has been found that most, if not all, of them, represent a single species that is very similar to Thyrsostachys oliveri, but is possibly not this species. They are provisionally separated and listed under → Thyrsostachys cf. oliveri. The leaves correspond in size to those of T. oliveri. From these specimens, three living plants were selected, which remained at Bambusetum Baan Sammi for further observation [as of August 2022, only two living specimens remained for further observation]. 

(7) Group 4: This group includes about five specimens from Thailand, obtained as living plants or as seeds. None of the specimens has already reached its maximum size. The leaf size corresponds to that of Thyrsostachys siamensis. Two specimens have glabrous culms and a culm-leaf sheath apex with a very steep curvature. No statement can be made about the other specimens, as the plants are still too small. All these specimens are listed under → Thyrsostachys siamensis.

(8) Group 5: These are the Thyrsostachys species that have been observed in areas outside of Bambusetum Baan Sammi. Their characteristics largely correspond to those of Group 1. The culms are so different in height that an assignment to T. oliveri or T. siamensis seems difficult. The one-year-old culms are covered with white fuzz, but it has repeatedly been observed that some internodes of a particular culm within a clump have developed fuzz while other internodes remain without any fuzz. The leaf size could not be observed or measured in detail, but the leaf size consistently corresponds more to that of T. siamensis than of T. oliveri.

Comments 2:

(1) Plants named by local people as ไผ่รวกแดง (phai ruak daeng), ไผ่รวกบ้าน (phai ruak ban), and ไผ่รวกป่า (phai ruak pa), clearly belong to the genus Thyrso­stachys. Whether or not there are distinguishing characteristics is currently not clear. The name phai ruak daeng (daeng = red) might refer to the sheath color of young culms, of which the lower ones are reddish green. Phai ruak ban (ban = house, village) is a tall bamboo often found planted in villages. Phai ruak pa (pa = wood, forest) is from the wild and was planted on the bamboo collection site of the Royal Project, Huai Hong Khrai (ห้วยฮ่องไคร้) Study Center, A. Doi Saket, Chiang Mai Province, where it actually grows less tall and less thick than their other plants of Thyrso­stachys. Whether these names can be assigned to Thyrso­stachys oliveri or Thyrsostachys siamensis is not clarified at present.

(2) Specimens at Kew: A total of 9 specimens from J. W. Oliver on Poaceae are recorded, all from "1892", all of them on sheets, and all identified as Thyrsostachys oliveri. All specimens show flowering and leafy branches, but no culm-leaf (culm sheath). The only available image of a culm-leaf is the line drawing in Plate No. 50 (in J. S. Gamble, Bambuseae Brit. India, 1896 [#1230]), and that drawing was based on J. W. Oliver's specimens in "1891" as stated by Gamble. — Kew Herbarium, accessed 6 Nov. 2020.

(3) Description and line drawing of culm-leaf by Gamble (l.c., 1896 [#1230]): Both the description and line drawing are confusing as they do not match species from Thailand identified as Thyrsostachys oliveri. Most of the characteristics described, and the line drawing, rather match with ไผ่เลี้ยง (phai liang), ×Thyrsocalamus liang Sungkaew & W. L. Goh (2018).

(4) Walls of culm-internodes: "walls rather thin" (according to Gamble, 1896 [#1230]). However, the walls of all observed plants from Thailand that are believed to represent either Thyrsostachys oliveri or Thyrsostachys siamensis are quite thick and even solid on the basal culm. Also, ×Thyrsocalamus liang, ไผ่เลี้ยง (phai liang), which some Chinese botanists consider being true Thyrsostachys oliveri, have rather thick walls and solid basal culms. In contrast to the basal, lower, and middle culm sections, the walls of the upper culm section are in fact relatively thin.

(5) Description of flowers: "… filaments purple …" (Gamble, l.c., 1896: p. 59 [#1230]). I would rather expect the filaments to be white and the spikelets purplish when young.

(6) Gamble stated that Thyrsostachys oliveri is easily recognized by being larger than Thyrsostachys siamensis. I suspect that there are plants of Thyrsostachys oliveri cultivated in Thailand, that only reach the height of Thyrsostachys siamensis or grow slightly higher. Therefore, it will be difficult to identify both species only by their statures.

(7) Seeds (BS-0752, June 2012, and BS-0752-1, May 2013) of the name Thyrsostachys oliveri were received from China and said to originate from Vietnam. The seeds covered by their husks are similar to seeds of several species, some of them labeled as Gigantochloa species, received from China in 2011. Still, in May 2014, seedlings raised from BS-0752 were too small to be identified, but the leaves show a size that is similar to T. oliveri or even somewhat longer and wider than one would expect in this species.

(8) Seeds of Thyrsostachys were occasionally collected in Thailand in recent years and were commonly considered as Thyrso­stachys siamensis by the collectors, but there are no records available on their proper identification. Some collectors said that the seeds were from "tall" plants. A Thyrsostachys bamboo near the Ping River in Mueang Chiang Mai District (Chiang Mai Province, northern Thailand) has been described as tall, flowering, and seed-producing, and was identified as Thyrsostachys oliveri, ไผ่รวกใหญ่ (phai ruak yai) by Jeera Makmee (Facebook, 2 Apr. 2022, by Jeera Makmee).

(9) Reliable flowering and seeding records of Thyrsostachys oliveri in China, Vietnam, Thailand, or elsewhere in the 2010s could not be found.

(10) The basal and lower culms of Thyrsostachys are tightly wrapped into culm-leaves that cannot be easily removed. However, as soon as one removes the culm-leaves, it becomes clear that branch buds are present on the very basal node and all upper nodes (→ photos BS-0002-1_S2_019.jpg, BS-0002-1_S2_020.jpg, BS-0002-1_S2_021.jpg).