Areca rheophytica

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Areca (ah-REHK-ah)
rheophytica (reh-oh-fih-TEE-kah)
Ar00141.JPG
Scientific Classification
Genus: Areca (ah-REHK-ah)
Species:
rheophytica (reh-oh-fih-TEE-kah)
Synonyms
None set.
Native Continent
Asia
Asia.gif
Morphology
Habit: Solitary
Leaf type: Pinnate
Culture
Survivability index
Common names
None.

Habitat and Distribution

Areca rheophytica is an undergrowth palm that, as the name states, is clearly a rheophyte plant
Nong Nooch Tropical Garden, Pattaya, Thailand. Photo by Dr. Scott Zona.
(aquatic plant that lives in fast moving water currents, such as in a stream or river, in an environment where few other organisms can survive) that grows in river banks on ultrabasic rocks. (llifle.com)

Borneo. Growing as a rheophyte on the banks of fast-flowing rivers and streams in areas of ultrabasic rock, in the lowlands and up to about 400 m above sea level. (J. Dransfield, The genus Areca (Palmae: Arecoideae) in Borneo. 1984)/Palmweb.

Description

Areca rheophytica is a small but most elegant solitary palm with arched feather like fronds. Stems: Finger-like glabrous, pale brown up to 2 m tall and 1-1.5 (-2) cm in diameter. With inconspicuous nodal scars about 3-5 mm hight, internodes 2-4 cm apart.

Crownshaft: 20-30 cm tall, 2-4 cm wide, enlarged and green. Crown: With 7-8 leaves.

Leaves.. Up to to 60 cm long, petiole short about 8-15 cm long, pinnae (leaflets) 12-22 regularly arranged on each side of the rachis, single ribbed, very close, dark green. Sheaths usually less than 25 cm, smooth when fresh, drying ridged.

Inflorescence: Erect usually less than 22 cm, The rachillae (flower-bearing branches) slender, very numerous,up to 120 mm long and 1 mm in diameter. Flowers grouped in one to several basal triad, otherwise bearing paired staminate flowers in a single row on one side. Staminate flower (male) creamy-white, lemon-scented; Pistillate flower (female) at anthesis about 11 x 3 mm tipped with 3 short stigmas.

Fruit: Narrow-ellipsoidal, approx 20 x 7 mm, pale green turning bright-red at maturity, mesocarp about 2-5 mm thick. Seed: Spindle-like approx 15 x 5 mm. (llifle.com)



Detailed Scientific Description

Solitary, short-stemmed, rheophytic, undergrowth palm, Stem to about 2 m tall, usually less, 1-2 cm in diam., pale brown except near the crownshaft where green, glabrous, internodes 2-4 cm, the nodal scars conspicuous about 3-5 mm high. Crownshaft usually swollen, 15-30 x 2-4 cm, pale green. Leaves about 7-8 in the crown; sheaths to 25 cm, usually less, smooth when fresh, drying ridged, bearing very sparse scattered scales; petiole 8-15 x 0.3-0.5 cm, channeled adaxially, rounded abaxially, bearing very sparse brown scales; leaflets 12-22 on each side of the rachis, dark green, close, regularly arranged, all single-fold except the apical pair and sometimes the basal pair which are 2-3-ribbed, concolorous, bearing very sparse, minute, brown scales scattered on both surfaces. Inflorescence erect at anthesis, to 22 cm, often less; prophyll to 25 x 3.5 cm, conspicuously winged, the wing margins somewhat erose and hairy towards the tip, the prophyll surface striate on drying, bearing scattered brown scales; peduncle 7-15 x 5 mm, winged at the very base; axis branching to 3 orders; rachillae slender, very numerous, to 120 x 1 mm, sometimes with a short bare portion at the base, usually with a basal triad, rarely with several triads, otherwise bearing paired staminate flowers in a single row on one side. Staminate flower narrow-ovoid, trigonous, creamy-white, citrus-scented; sepals 3, free, triangular, keeled, about 0.8 x 0.4 mm; petals 3, striate, narrow-triangular, about 2.2 x 0.7 mm; stamens 6, filaments very short, anthers elongate, about 1.4 x 0.3 mm; pistillode trifid, conspicuous, exceeding the stamens, about 1-8 X 0-3 mm. Pistillate flower at anthesis narrow, trigonous, about 11 x 3 mm; sepals 3, free, imbricate, about 7 x 4 mm; petals 3, exceeding the sepals, about 10 x 6 mm, imbricate, with short triangular, valvate tips; ovary fusiform, about 10 x 3 mm, tipped with 3 short stigmas. Fruit fusiform, pale green at first, at maturity becoming cherry-red, narrow-ellipsoidal, about 20 x 7 mm; mesocarp becoming < 2-5 mm thick; seed fusiform, about 15 x 5 mm. (J. Dransfield, The genus Areca (Palmae: Arecoideae) in Borneo. 1984)/Palmweb. Editing by edric.

The relationships of the rheophytic Areca of Sabah are clearly with hexandrous species of Arecella (in Furtado's sense); it seems closest to A. hutchinsoniana and A. vidaliana of the Philippines. A. hutchinsoniana does not have rheomorphic unicostate leaflets and so is easily distinguished. A. vidaliana on the other hand is much more difficult to separate, and I had originally thought the Sabah taxon was conspecific with it. Beccari (1907) described two closely related species from Palawan - A. vidaliana with broad leaflets, and A. mammillata with unicostate leaflets. Later (1919) he sank the latter into the former, having noted how variable is the leaf dissection in Areca. Merrill (1922) for no apparent reason cited A. vidaliana as a synonym of A. mammillata rather than vice versa. In 1979 I had the opportunity to see A. vidaliana in the field in Palawan. Near Puerto Princesa it grows in small crown forest rich in bamboo (Schizostachyum sp.) developed on serpentine rock, and occurs in a variety of forms ranging from unicostate to broad- costate. In habitat and aspect it is very different from the Sabah rheophyte. It is worth stressing that there was no rheophytic Areca sp. in the area I visited, though the habitat was abundant. Although I have found difficulty in separating what are geographically and ecologically distinct taxa, I still believe the Sabah taxon is sufficiently distinct to be accorded specific status. At present, true A. vidaliana is known from Malaysian territory only from P. Balembangan between the coast of Sabah and Palawan. A. rheophytica is a most elegant species. Professor van Steenis wrote to me in relation to the preparation of his book on rheophytes (van Steenis 1981) concerning this taxon. At the time I had not seen it in the field, and as I assumed it to be non-rheophytic A. vidaliana the taxon was not included by Professor van Steenis. (J. Dransfield, The genus Areca (Palmae: Arecoideae) in Borneo. 1984)/Palmweb.

Culture

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Cultivation and Propagation: This is an excellent understory palm very highly sought after by palm collectors, but scarcely known in cultivation.

Soil: They prefers well draining, porous soils rich in humus. (but can even grow in soggy terrain). Light: They do well in shade or half-sun spots, but keep their best deep green colour in full shade, if indoors place in a luminous position. Seedlings like a more sheltered area.

Watering: In cultivation they appreciates abundant waterings. During the summer or warmer months, water frequently to keep the soil from drying out. Fertilization: Need a perfect fertilizer diet including all micro nutrients and trace elements or slow release fertilizer. Apply fertilizer 3 times a year, in spring, summer and fall...and if the palm is planted in full sun, fertilize more often. In a full sun location the fronds tend to turn lime-green or yellow, so the extra fertilization helps prevent this discolouration.

Hardiness: It can be difficult to get it to look its best without a great amount of heat and sun and so it is only really suited to the tropics in frost-free regions (USDA Zones 11-12)

Maintenance: These palms aren't considered self-cleaning but you'll only need to trim off an old frond occasionally.

Garden uses: It is rarely cultivated, but is an excellent understory palm if you can water it regularly. It is ideal where garden space is limited and a small plant is required. It can be grow indoors in a container for years before out growing the pot, but looks much better when planted in the ground and will thrive if given a spot in shade. (llifle.com) Cold Hardiness Zone: 10b

Comments and Curiosities

Remarks: Only a few palms have been described as rheophytes, among them Pinanga rivularis and Pinanga tenella from Borneo, Chamaedorea cataractarum from Mexico, Geonoma linearis from Colombia and Ecuador, Dypsis crinita and Ravenea musicalis both from Madagascar. (llifle.com)



  • IMAGE GALLERY

  • Tungud, Sabah, Malaysia. Photo by Dr. John Dransfield, Royal Botanic Gardens, Kew/Palmweb.

  • Tungud, Sabah, Malaysia. Photo by Dr. John Dransfield, Royal Botanic Gardens, Kew/Palmweb.

  • Photo by Dr. John Dransfield, Royal Botanic Gardens, Kew/Palmweb.

  • Nong Nooch Tropical Garden, Pattaya, Thailand. Photo by Dr. Scott Zona.

  • Photo-amazonia-online.com

  • Photo-amazonia-online.com

  • Photo-amazonia-online.com

  • Photo-amazonia-online.com

  • Photo-imageflora.com

External Links

References

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).

J. Dransfield, The genus Areca (Palmae: Arecoideae) in Borneo. 1984


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

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