Hydriastele rheophytica

Hydriastele (high-dree-Ah-STEL-eh) rheophytica (reh-oh-fih-TEE-kah)
Hydriastele rheophytica. A. Habit. B. Inflorescence and infructescences. C. Infructescence. All from Baker et al. 1436 (cultivated specimen). All photos: W.J. Baker. PETER PETOE, CHARLIE D. HEATUBUN & WILLIAM J. BAKER Phytotaxa 370 (1) © 2018 Magnolia Press.
Scientific Classification
Genus: Hydriastele (high-dree-Ah-STEL-eh) Species: rheophytica (reh-oh-fih-TEE-kah)
Synonyms
None set.
Native Continent
Oceania
Morphology
Habit: Clustering (soboliferous) Leaf type: Pinnate
Culture
Survivability index
Common names
None.

Habitat and Distribution

Hydriastele rheophytica distribution:—Known from the Idenburg River and its upper tributaries in Papua Province, western New Guinea. Also reported from the Frieda River in the adjacent Sandaun Province of Papua New Guinea (Dowe & Ferrero 2000b). PETER PETOE, CHARLIE D. HEATUBUN & WILLIAM J. BAKER Phytotaxa 370 (1) © 2018 Magnolia Press.

Habitat:—Stream and river banks frequently

Hydriastele rheophytica. A. Habit. B. Inflorescence and infructescences. C. Infructescence. All from Baker et al. 1436 (cultivated specimen). All photos: W.J. Baker. PETER PETOE, CHARLIE D. HEATUBUN & WILLIAM J. BAKER Phytotaxa 370 (1) © 2018 Magnolia Press.

subjected to inundation, about 850 m. PETER PETOE, CHARLIE D. HEATUBUN & WILLIAM J. BAKER Phytotaxa 370 (1) © 2018 Magnolia Press.

Description

Clustering, rheophytic palm forming clumps of as many as 30 stems, slender, to 6 m tall, bearing 4–12 leaves per crown. Stem 2–2.5 cm in diam., pliable and mostly leaning. Leaf ca. 95–120 cm long including petiole; sheath 40–45 cm long, petiole 20–30 cm long, pliable; leaflets 18–32 per side, arranged regularly, linear, thin and soft; basal leaflets single-fold, obliquely praemorse apically; terminal leaflets comprising 2 or 3 folds, truncately praemorse apically. Inflorescence 16–30 cm long including 2.5–7 cm peduncle, branched to 1 or 2 orders, protogynous; rachillae 5–15 per inflorescence; triads opposite and decussate. Staminate flower 6–8 × 3–4 mm (when dry); stamens 6. Pistillate flowers 2–2.5 × 2 mm in bud (when dry), with free sepals and free, ± rounded, low petals. Fruit ca. 7 mm long, globose to broadly ellipsoid, with inconspicuous stigmatic apical remains lacking encircling dark sclerotic zone. Seed globose; endosperm shallowly ruminate. PETER PETOE, CHARLIE D. HEATUBUN & WILLIAM J. BAKER Phytotaxa 370 (1) © 2018 Magnolia Press.

An attractive dainty clustering palm to 3 meters (10 ft.) - very reminiscent of some of the moderate clustering Dypsis, with finely pinnate leaves and slender flexible stems. Editing by edric.

Culture

As the name and habitat suggests, it is a water lover and can tolerate areas of frequent inundation and some water flow. Shady, and moist; preferably tropical, but not necessarily. Cold Hardiness Zone: 10b

Comments and Curiosities

Notes:—Hydriastele rheophytica is restricted to riverbanks where it forms large clumps of pliable, somewhat leaning stems. Only one other member of the genus, H. simbiakii, has a similar habitat preference although that species belongs to the Nengella group. Hydriastele rheophytica is distinguished by its leaves with numerous thin and soft, linear leaflets, the basal ones of which are obliquely praemorse at their tips, and a terminal leaflet pair comprising 2 or 3 folds. This species is most similar to H. variabilis, but that species has erect, non-pliable stems and terminal leaflets comprising 4–11 folds and it is not rheophytic. A Brass photo showing H. rheophytica in its native habitat was reproduced in Rheophytes of the World (van Steenis 1981). The species is described in more detail by Dowe & Ferrero (2000b) and Petoe et al. (2018). PETER PETOE, CHARLIE D. HEATUBUN & WILLIAM J. BAKER Phytotaxa 370 (1) © 2018 Magnolia Press.

Uses:—Cultivated as an ornamental following introduction to Australia in the 1980s (Dowe & Ferrero 2000b). PETER PETOE, CHARLIE D. HEATUBUN & WILLIAM J. BAKER Phytotaxa 370 (1) © 2018 Magnolia Press.

"Very ornamental dainty New Guinea palm, only recently described, but already showing up in lots of Hawaiian gardens... has fine, very evenly spaced leaflets; canes always seem to be leaning one way or another. New leaves open up a glossy olive red-green and petioles are ornamentally spotted like they've been spray-painted. Lives along river banks in nature but seems to grow fine in non-wet conditions in the tropics." (Geoff Stein)

Rheophytes (which means plant growing in/near running streams), typically have finely pinnate leaves, and very flexible stems, so that when the river floods, they present very little resistance to the flow, they just bend with it, rather than breaking.