Rhapis siamensis

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Rhapis (RAH-pis)
siamensis (siam'-en-sis)
Thailand. Photo by Cindy Adair.
Scientific Classification
Genus: Rhapis (RAH-pis)
siamensis (siam'-en-sis)
None set.
Native Continent
Habit: Clustering
Leaf type: Costapalmate
Survivability index
Common names

Habitat and Distribution

Native to, Thailand. Rhapis siamensis is restricted to moist and wet forest on
Thailand. Photo by Philippe Alvarez.
limestone hills in middle peninsular Thailand from 20·200 m elevation. Considerable variation exists within populations. Plants growing in depressions between limestone boulders where soil and humus have accumulated are taller and more robust, and have larger leaves with more segments than plants growing a few meters away in a more exposed location with little or no soil and humus. R. siamensis is similar to R. micrantha but the latter differs in its leaf blade with segments free to the base, the globular pistillate flowers with obovate petals, and the fleshy calyx. (A New Species from Vietnam by Dr. Andrew J. Henderson 2008)


Clustered, dioecious, understory palm forming dense clumps 3-5 x 1-2 m. Stems often covered with persistent, fibrous sheaths, 6-15 mm in diam. without sheaths, 1.8-2.5 cm in diam. with sheaths, ringed, internodes 1-5 cm long, yellowish green. Leaves 15-22, spreading, palmately divided; sheath 5-12 cm long, long-open, margins fibrous-netted, fibers dark brown and in 3 layers, outermost coarsest, middle and innermost finer; petiole 30- 50 cm long; blade 15-28 x 25-50 cm, +/- semi- orbicular, divided 3/4 to nearly to base into (5-) 8-12 segments, these (12-) 18-20 (-24) x 0.5-5 cm, truncately praemorse, glossy green adaxially, paler abaxially, 1-4-nerved, 12-24 nerves total per blade, transverse veinlets conspicuous, close-set, 1-2 mm distant. Inflorescences 2-3, interfoliar, spreading; staminate 40 cm long, peduncle 20 cm long, flattened, 7 mm wide; prophyll 15 cm long, attached 9 cm above base of peduncle, tubular, obliquely open apically, thin-papery, reddish brown to brown with deciduous, twisted, slender, whitish hairs 2.54 mm long at apex and along both slightly winged margins, peduncular bract 1, similar to prophyll, 1-6 em long, attached 7 cm above base of prophyll and extending on to rachis 3-4 cm; rachis 1-3 cm long with 2 main branches, one with bract similar to peduncular bract and inserted 1.5 cm above branch base; rachillae 13-28, these 10-15 cm long, lower ones sometimes furcate; pistillate inflorescence similar to staminate only to 25 cm long and with 3-7 rachillae 10-12 cm long. Staminate flowers seen in young bud, 1.5 mm high; calyx 1 mm high, Culpular. Pistillate flowers in 2 spiraling rows, mostly solitary, 4-7 mm distant, placed on a pedicel 0.5 mm high, 4.5 x 1.5 mm, narrowly ovoid; calyx 1.5 x 1.5 mm, crown-like, prominently lobed, sepals connate in basal 1/2, broadly folded apically, acute, mucronate; corola 4.5 nun high, petals connate below and at tip initially, corolla opening by apical slits, petals valvate, later spreading apically, long-<lvate, acute, +/- fleshy; calyx and corolla prominently nerved when dry; staminodes 6; pistil 2 x I mm, short- columnar, angular, composed of separate carpels; stigma short with 3, poorly developed lobes. Fruits immature, 7.5 x 44.5 mm, ovoid, green; fruiting perianth an expanded, canpanulate tube 3 mm long, lobes spreading, staminodes just exceeding corolla. (A New Species from Vietnam by Dr. Andrew J. Henderson 2008), Editing by edric.


Cold Hardiness Zone: 10a

Comments and Curiosities

subtilis or siamensis

2-13 leaflets

(1) blades split to the base (if blades not split > R. siamensis)

(2) pointed apices of leaflets

(3) ligules sometimes persistent

(4) stem to 2 cm diameter, if to 2.5 cm only siamensis

Notations by Research Work Editor palMeir.

Etymology: The epithet is from the word Siam, the former name for modern-day Thailand. (A New Species from Vietnam by Dr. Andrew J. Henderson 2008)

A new species described in 1997.

External Links


Phonetic spelling of Latin names by edric.

Special thanks to Geoff Stein, (Palmbob) for his hundreds of photos.

Special thanks to Palmweb.org, Dr. John Dransfield, Dr. Bill Baker & team, for their volumes of information and photos.

Glossary of Palm Terms; Based on the glossary in Dransfield, J., N.W. Uhl, C.B. Asmussen-Lange, W.J. Baker, M.M. Harley & C.E. Lewis. 2008. Genera Palmarum - Evolution and Classification of the Palms. Royal Botanic Gardens, Kew. All images copyright of the artists and photographers (see images for credits).

Many Special Thanks to Ed Vaile for his long hours of tireless editing and numerous contributions.

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