Dendrocalamus khoonmengii
Dendrocalamus khoonmengii Sungkaew, Teerawat. & Hodk., Thai Forest Bull., Bot. 35, 2007: 99 [#1060].
Thai names: ไผ่กระโรม (phai kra rom); ไผ่ปูนผาตากผ้า (phai pun pha tak pha); "phai mung". — T. Smitinand, 2001 [#1003]; BKF [#1368].
Distribution: THAILAND (South): Nakhon Si Thammarat Province: Khao Luang National Park, on steep slopes by the river, at 100 m altitude.
Description: "Rhizomes pachymorph. Culms unicaespitose, in a loose clump, up to 13 m long, 3–4 cm in diam., with relatively thin walls, culm tips strongly arching over; internodes 35–50 cm long, plain green, copiously white-waxy all over in very young stages, glabrous and waxless when older, lower internodes not covered with hairs; nodes not swollen, lower nodes without verticils of roots, the region directly below each node of young culm with a band of black hairs. Branches developing from mid-culm or from lower quarter upwards; branch complement at mid-culm of one dominant primary axis with two secondary, weaker axes from its base and several smaller higher-order branchlets, the dominant primary axis long and slender, reaching 3–5 m long, much longer than other axes; without aerial roots. Culm-sheaths pale pinkish to greenish to orange, covered with black hairs mainly on the lower half and copious white wax all over, deciduous, coriaceous, 15–25 by 10–15 cm, top convexly truncate; blades green, narrowly lanceolate, spreading to reflexed, 15–20 by ca 2 cm (width near the base), sparsely hairy near the base on the adaxial surface; auricles purplish-black, lobe-like, 1–1.5 by 0.2–0.7 cm, somewhat curved, slightly twisted, and free at the ends, margin with pale brown bristles to 7–10 mm long; ligule pinkish purple, 3–12 mm long, irregularly toothed, some divisions further divided into fine bristles, about 5 mm long. Leaves 5–10 per branch; leaf blades narrow, 5–12 by 0.4–1.2 cm, upper surface glabrous to sparsely hairy, lower surface glaucous and covered with short and fine hairs and scattered with long hairs to 1 mm long, apex acuminate, margin serrate, base rounded to oblique-cuneate; sessile or with pseudopetiole to 1 mm long; auricles absent or just tiny rims, fringed with a few wavy bristles to 3.5 mm long; ligule about 0.1–0.3 mm long, irregularly toothed; secondary veins 2–4 pairs, intermediate veins 4–7; leaf sheaths 2–3 cm long, hairy. Inflorescences unknown." — S. Sungkaew & al., in Thai Forest Bulletin (Botany), 35, 2007: p. 98-102 [#1060].
Images: Line drawing in S. Sungkaew & al., in Thai Forest Bulletin (Botany), 35, 2007: p. 100 [#1060]. Photo in S. Sungkaew, BRT Biodiversity (shoot) [#1343], and in Kasetsart Univ. Forestry (shoot).
Characteristics: Similar species are Dendrocalamus pendulus, Dendrocalamus hirtellus, Dendrocalamus dumosus, and Dendrocalamus elegans. The primary distinctive characteristics of Dendrocalamus khoonmengii "are its projecting, curved and lightly twisted culm sheath auricles, and its abaxially glaucous leaf blades" (S. Sungkaew & al., l.c., 2007: p. 102-103 [#1060]). The auricles can be seen from the line drawing (S. Sungkaew & al., l.c., 2007: fig. 1, p. 100 [#1060]).
Comments:
(1) Flowers were unknown when the species was published in 2007. By late 2016, no records of flowering and seeding of this species were known (Sarawood Sungkaew, pers. comm., 20 Dec. 2016).
(2) The species was named in honor of Khoon Meng Wong, a botanist from Malaysia.
(3) Several plants (BS-0541, BS-0358), received under the name Dendrocalamus khoonmengii from the wild of Satun Province in 2010, still need to be examined to determine if they truly represent this species or, more likely, represent a different species.
Dendrocalamus aff. khoonmengii
Comments: The following specimens (BS-0541 etc., BS-0288, etc., BS-0700, etc., BS-0531, BS-0532) have been provisionally placed near Dendrocalamus khoonmengii for their overall similarities with this species, and mainly for their conspicuous protruding culm-leaf auricles. However, the shape of the culm-leaf auricles is different (but seems neither to fit with Dendrocalamus dumosus and Dendrocalamus elegans), flowers and seeds are known from 3 specimens (whereas flowers and seeds are unknown in Dendrocalamus khoonmengii), and culm and branch internodes are solid to moderately thick-walled (but thin-walled in Dendrocalamus khoonmengii).
Dendrocalamus aff. khoonmengii pop. Songkhla
Specimens: BS-0541 [†] (living plants, died from flowering) = CS-3043, เขาพระ (Khao Phra), Songkhla Province ["Kha Phra, Satun", in err.], southern Thailand, wild, collected by C. S. in 2010, received via ธ. ล. as "Dendrocalamus khoonmengii", 30 May and 12 Nov. 2010; seeds collected from two flowering plants (BS-0541) by D. O., harvesting seeds from early 2012 to mid-2013 (BS-0541A), and between 29 Jan. and 8 May 2014 (BS-0541B). BS-0541A [C5] and BS-0541B [BBG] (living plants, both seedlings raised from seeds of BS-0541).
Characteristics: Habit caespitose, a somewhat open clump. Rhizome pachymorph, moderately long. Culms upright below, widely arching and scandent above. Young shoots emerge from June to November(?). Culm-internodes about 40 cm long, terete, green, glabrous, smooth, slightly covered with a white mealy deposit when young (the mealy deposit of internodes and culm-leaf sheaths is said to be somewhat fluorescent), very thick-walled, solid or nearly so at the basal culm (wall thickness 5 mm at the 7th internode of 4.0 cm diameter, 1.4 m above the ground). Culm-nodes slightly prominent; sheath scar a prominent corky ring, shiny black when young, dull light brownish when old; basal nodes occasionally with aerial roots. Branch-buds solitary, from the basal node up. Branches: Lower culm usually unbranched, mid and upper culm with few to many subequal branches, the central branch dominant, widely arching to the ground and scandent; branching intravaginal. Culm-leaves deciduous. Culm-leaf sheaths almost as long as the internode, usually glabrous, occasionally with a few blackish hairs, light green and slightly farinose when young; apex truncate, junction with the blade about 1/3 the width of the apex. Culm-leaf auricles prominent, blackish, projecting, sickle-shaped, and long pale bristly. Culm-leaf ligule short, horizontal, edges long-bristly, middle part short-bristly. Culm-leaf blades horizontally patent to reflexed, deciduous. Foliage-leaves (5–) 7 (–12) per branchlet. Foliage-leaf sheaths glabrous or minutely hairy. Foliage-leaf auricles inconspicuous lobes, with a few long pale bristles, 3–5 (8) mm. Foliage-leaf ligule inconspicuous, entire. Foliage-leaf blades 7–17 × 1.0–1.6 cm, occasionally slightly bigger, green above, somewhat bluish-green beneath, glabrous above, finely pubescent beneath when young, linear-lanceolate; base rounded to wedge-shaped; margins antrorsely scabrous; apex acuminate to attenuate; pseudopetiole very short, 0.2–1 mm. Pseudospikelets small, arranged in tufts on leafless branches. Anthers red. Filaments white.
BS-0541: Upper section of a young culm-leaf showing a projecting, large sickle-shaped auricle with long pale bristles, and a denticulate ligule with erect pale bristles of different lengths; blade horizontally patent
Cultivation requirements: Plants grow well on normal garden soil with a neutral pH. A test revealed that plants (seedlings of BS-0541B) also grow well on highly alkaline soil (10 pH).
Seed weight: 10 g ≈ 650–730 dried spikelets (husk-wrapped seeds).
Seed viability: Over 1 year.
Seed germination: (1) Seeds (BS-0541A) placed on moistened tissue paper, in late January 2012, 24–31 °C day, diffuse light, 12–20 °C night, atmospheric humidity >70%, the first shoot emerged after 17 days, possibly delayed by initially low temperatures. The germination rate was very high (>95%, by early April 2012). The germination rate was over 70% in October 2012, and over 40% in March 2013. — (2) 10 seeds (BS-0541B) placed on moistened tissue paper, 31–36 °C day, diffuse light, 20–25 °C night, atmospheric humidity >70%, the first shoot emerged on the 4th day, 5 seeds have sprouted by the 7th day, 9 by the 12th day (test 140407). — (3) pH tolerability test (Jul. – Sep. 2014): Seedlings (BS-0541B) grow well on a high alkaline growth medium (10 pH).
Comments:
(1) Several plants of the Satun population were received in 2010, of which all but one flowered (starting Nov. 2011) and died (the last plant in June 2013). The first seeds were collected on 27 Jan. 2012, and the latest seeds in mid-2013. Seedlings were raised (BS-0541A). The single, hitherto non-flowering plant started flowering (in late 2013) and, after seeding, died (mid-2014). Seeds were collected on 29 Jan., 10 Mar., 19 Apr., and 8 May 2014, and seedlings were raised (BS-0541B). The seedlings turned out to be robust plants, growing well on normal garden soil (Aug. 2013).
(2) Characteristics of the culm sheath, e.g., length and auricles, are different from all the other plants assigned to Dendrocalamus dumosus and D. elegans, whereas other vegetative characteristics are rather similar.
(3) The characteristics recognized on immature plants are similar to Dendrocalamus khoonmengii, except internodes are (moderately) thick-walled to solid, aerial roots may occur on basal culms in plants of the Satun population, and the flowers of D. khoonmengii are still unknown, hence not yet described. When the plant matured, it became unlikely that BS-0541 represented D. dumosus, as the culm sheaths developed projecting, curved auricles.
(4) Seeds from plants of the Satun population are morphologically similar to Dendrocalamus membranaceus and D. barbatus, but are much smaller, and 100 seeds weigh only 1.4–1.5 g.
(BS-0541A): seedling (left) and seeds (right) from the Satun population
(BS-0541B): 9 of 10 seeds germinating, 18th day
Dendrocalamus aff. khoonmengii pop. Langkawi
Specimens: BS-0288 [†] (living plants, died after flowering) = CS-2001, Malaysia (Peninsula, north), Langkawi Island (เกาะลังกาวี), wild, collected by C. S. in Aug. 2008, received as "Dendrocalamus elegans" in Aug. 2009; seeds from a single flowering plant of BS-0288 collected by D. O., from mid-Mar. 2012 to Apr. 2013; BS-0288A [-], BS-0288B [-], BS-0288C [W3] (seedlings), Aug. 2012; BS-0288D [SSG] (seedling), striped leaves, Sep. 2013.
Characteristics: Habit caespitose. Rhizome pachymorph. Culms straight, more or less erect below, scrambling above [ultimate length not yet known]. Young shoots reddish. Culm-internodes glabrous, smooth, mid-green to dark green, 27–38 cm long (on culms in a 5-year-old clump), solid on the basal culm, very thick-walled to solid on the lower culm (walls 3 mm thick, lacuna 5 mm, diameter 11 mm on the 4th internode 63 cm above the ground), moderately thick-walled on the mid-culm [ultimate diameter not yet known]. Culm-nodes glabrous, smooth, slightly prominent, sheath scar a slightly protruding corky ring, 1–2 mm high, shiny black when young, dull light brownish when old; supranodal line discernible, without a ridge, 4–5 mm above the nodal line; aerial roots none. Branch-buds solitary, present from basal nodes up. Branches usually none on the basal and lower culm, initially 1 on the lower or mid-culm, 1/2 to 2/3 as thick as the main culm, mid-culm and upper culm with several branches, the central branch much dominant and elongating, with 2 smaller lateral branches, and several thin, subequal branches 0.5–2 mm thick; branch nodes prominent; branching intravaginal; rebranching. Culm-leaves deciduous. Culm-leaf sheath about 13 cm long, 1/2 as long as the internode or a little shorter, thickly papery, reddish, and sparsely blackish hairy when young, apex truncate. Culm-leaf auricles conspicuous, dark, long pale bristly. Culm-leaf ligule short, dark, entire, with a few pale bristles when young. Culm-leaf blade usually horizontally patent or reflexed. Foliage-leaves (5) 7–9 (13) per branchlet. Foliage-leaf sheath short pale hairy when young, glabrous when old. Foliage-leaf auricles small crescent protruding lobes, 1–2 mm long, with spreading pale bristles 3–5 mm long. Foliage-leaf ligule short, inconspicuous, occasionally with a few long straight pale bristles. Foliage-leaf blades mid-green to dark green on both surfaces, 9–15 (20) × (0.5) 1.0–1.9 (2.7) cm, densely and finely velvety hairy beneath when young, glabrous when old, linear-lanceolate; base rounded to wedge-shaped; margins antrorsely scabrous; apex attenuate; midrib proximally slightly prominent on both surfaces, light green beneath; pseudopetiole short, 1–2 mm.
Seed weight: 10 g ≈ 650–730 dried spikelets (husk-wrapped seeds).
Seed viability: Over 1 year.
Seed germination: The germination rate was over 70% in October 2012, and over 40% in March 2013.
Comments: This clone (BS-0288) flowered in cultivation with all its plants from Jan. 2012 until May 2013, then died. A new generation (BS-0288A, BS-0288B, BS-0288C, BS-0288D) was raised from seeds. The plants produced did grow well on normal garden soil.
BS-0288: Upper section of a young culm-leaf showing a projecting, sickle-shaped auricle with long pale bristles, and a denticulate ligule with a few erect pale bristles of different lengths; blade reflexed
Seeds (BS-0288A)
Dendrocalamus aff. khoonmengii pop. Satun
BS-0700 (left): One of the 6-month-old seedlings with an unbranched leafy culm showing large blackish projecting sickle-shaped auricles with long pale bristles, very similar to BS-0541.
BS-0700-2 (right): The same type of auricle can also be seen in a young culm-leaf of the culm from the 4-year-old seedling BS-0700-2
Specimens: BS-0700 [BBG, SSG], BS-0700-1 [S5], BS-0700-2 [-], BS-0700-3 [BBG] (living plants), raised from seeds (received 21 Mar. 2012) collected by ธ. ล. from the grounds (from the uppermost litter layer of the forest soil horizon, which contained numerous seeds) of a flowering, wild population in สตูล Satun Province, southern Thailand, without precise locality, in Feb./Mar. 2012. Assumed by ธ. ล. being "Dendrocalamus khoonmengii".
Characteristics: Habit caespitose. Rhizome pachymorph. Culms more than 6 m long [ultimate length not yet known], straight, erect below, bending and leaning above, top drooping. Young shoots usually emerge green, occasionally emerge deep brownish-green or blackish, then fade to dark green with age. Culm-internodes mid-green to dark green, glabrous, thinly farinose when young, slightly flattened on the bud-bearing side, 20–25 (30) cm long, diameter (1) 1.5–2.5 (2.7) cm [ultimate diameter not yet known]; culm-wall thickness varies, usually solid with a small lumen. Culm-nodes slightly prominent, sheath scar corky, blackish when young. Branch-bud solitary, subrotund, from the base up. Branches typically none on the basal and lower culm, 1 branch (rarely 2 branches) on the mid-culm, much dominant, 1/3 to 2/3 as thick as the main culm, elongating, upper culm with few to several thin subequal short branches; branching intravaginal. Culm-leaves deciduous. Culm-leaf sheath 1/4–1/2 as long as the internode of the lower culm, reddish when young, covered with blackish hairs (some hairs initially pale); apex truncate, junction with the blade about 1/3 the width of the apex. Culm-leaf auricles blackish when young, conspicuous, protruding, pale bristly, bristles 2–5 (–10?) mm long. Culm-leaf ligule short, 1 mm, orange-red when young (blackish in BS-0700-1), denticulate, with a few short pale bristles. Culm-leaf blade slightly to horizontally patent. Foliage-leaves 10–12 per branchlet. Foliage-leaf sheath glabrous. Foliage-leaf auricles conspicuous, caducous with age, blackish, with 5 mm long pale early caducous bristles. Foliage-leaf ligule short, 0.5 mm, blackish. Foliage-leaf blade glabrous on both surfaces, or sparsely pilose above and finely pubescent beneath when young, (9–) 12–21 × 1.2–2.0 cm, occasionally larger, to 23.5 cm long, to 2.9 cm wide, linear to linear-lanceolate, base rounded to wedge-shaped, margins antrorsely scabrous, apex long attenuate; pseudopetiole short, 1–2 mm.
Seed weight: Not recorded.
Seed viability: Over 1 year (assumed, not tested).
Seed germination: Numerous seedlings were raised in 2012, but the germination process was not documented.
Comments:
(1) The above characteristics are based on 9-year-old seedlings.
(2) Culm wall thickness:
BS-0700: An about 2.5 m long section of a thick old culm (photo BS-0700_02) from the location where the seeds were collected is solid on its base (photo BS-0700_03) and rather thick-walled at its other end (photo BS-0700_04).
BS-0700-1: A thin culm with a diameter of 4–5 mm in the 4.5-year-old seedling is not solid on the basal culm but with a wall of 1.5 mm, on the lower culm with a wall of 1 mm, and on the mid-culm and upper culm with walls 1–0.5 mm (21 Sep. 2017). In the 9-year-old seedling, the culms and branches are generally solid or nearly so, with a small lumen (to 1.5 mm), but in thinner culms, the lumen may be wider (e.g., culm diameter 9 mm, wall 2 mm, lumen 5 mm).
BS-0700-2: A seedling with over 6 m long culms and a diameter to 2.7 cm: Solid throughout (culms and branches), very rarely with a tiny lumen of 0.1 mm in diameter (27 Apr. 2021).
Litter containing spikelets with seeds from the Satun population 2 (BS-0700)
A section of a flowering branch from the litter (BS-0700)
Seed-containing spikelets (BS-0700)
Seedlings from Satun population 2 (BS-0700): Seedlings 1 week old (above), and 3 months after (below)
Seedlings from the Satun population 2 (BS-0700): Seedlings 10 months after
Dendrocalamus aff. khoonmengii pop. Phuket
BS-0531: Foliage-leaves
BS-0532: Upper section of a young culm-leaf showing a projecting, sickle-shaped auricle with long pale bristles, the denticulate ligule not clearly visible; blade horizontally patent
BS-0532: Habit
Specimens: BS-0531 [†] (living plants) = CS-3031, Nai Han Beach (หาดในหาน), southern Phuket, southern Thailand, wild, received as "Dendrocalamus elegans", 26 May 2010; died because of flooding in 2017. BS-0532 [W3] (living plants) = CS-3032, same location.
Characteristics: Habit caespitose, a moderately tight clump. Rhizome pachymorph. Culms up to 18 m long or a little longer, erect below, bending and leaning above (→ table with culm size dimensions). Young shoots reddish, farinose, sparsely hairy; emerge from March to August/September. Culm-internodes thickly covered with a white mealy deposit when young, long-lasting, appearing bluish, green, and smooth when old, 28–46 cm long, diameter 2.5–3.2 cm on the basal and lower culm, slightly thicker on the mid-culm (from a height of about 2 m), thin-walled to moderately thick-walled only on the lower mid-culm, walls become relatively thicker and finally solid towards both the base and apex. Culm-nodes not or slightly prominent; sheath scar a somewhat corky ring, blackish when young. Branch-buds solitary, from the basal nodes up. Branches on the lower culm (for about 5 m) usually none, with 1–2 dominant elongating branches on the mid-culm and upper culm, with additional 2–3 thin subequal branches on the upper culm; branching intravaginal. Culm-leaves early deciduous. Culm-leaf sheaths about 1/2–3/4 as long as the internode, farinose and light green when young, straw-colored when dry, scattered with short dark hairs; margins short pale to dark ciliate; apex horizontally or concavely truncate. Culm-leaf auricles conspicuous sickle-shaped protruding lobes, blackish when young, margins with long straight or slightly waved pale bristles. Culm-leaf ligule short, blackish when young, denticulate, tapering into short straight pale bristles, edges with a few long straight pale bristles. Culm-leaf blades patent to reflexed, green when young. Foliage-leaves (5–) 7 (–13) per branchlet. Foliage-leaf sheaths minutely hairy when young, glabrous when old. Foliage-leaf auricles inconspicuous or lacking, without bristles. Foliage-leaf ligule inconspicuous, short, subentire. Foliage-leaf blades linear-lanceolate, 6–13 (18) × 0.7–1.0 (1.4) cm, glabrous above, pubescent(?) beneath when young, glabrous when old; base rounded to wedge-shaped; margins antrorsely scabrous; apex long-acuminate; pseudopetiole 0.5–1 mm. Flowers and seeds are unknown.
Comments: The above characteristics are based on 6-year-old plants grown from plant divisions, the culm length of 18 m was measured on 2 cut culms in July 2018.