Ravenea glauca
| Ravenea (rah-vehn-EH-ah) glauca (GLAH-kah) | ||||||||
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 Habitat, Madagascar. | ||||||||
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Contents
Habitat and Distribution
Central-South Madagascar: west side of Andringitra Mts and Isalo. Dry forest and in
Ravenea glauca is endemic to seasonally dry forest and extremely deep ravines and canyons in south central Madagascar at elevations from 2200 to 4000 ft.
Description
Some have adopted a common name of "Mini-Majesty" thinking this species is a smaller version of Ravenea rivularis. However, the two have little in common, with the former possessing a much more delicate appearance and much slimmer trunk. Neither does R. glauca share its "big brother's" affinity for water. The "glauca" in the binomial refers to the glaucous blue appearance of the new growth and the coloring these sometimes retain when grown in a hot, dry location. As can be seen from the photos, this species can attain heights more than the 15-26 ft that most references claim, on a slender 3-4 inch trunk (6-8 inch in cultivation). They can hold as many as 18-20 graceful 4-6 ft long leaves on 3-6 inch petioles. Editing by edric.
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Slender palm. TRUNK 0.2-8 m tall, rarely with sheath remnants in the distal part, 7-12 cm. in diam.; basal boss to 10 cm high, 18 cm across; internodes 2-5 cm, brown-grey; nodal scars 0.7-2 cm light brown; wood hard. LEAVES 14-20 in the crown, porrect and spreading, slightly arching; sheath 10-50 x 7-10 cm, white-floccose, with variously-sized remnants of more distal sheath material; petiole 10-50 cm, proxi mally 1.5-2.5 x 0.8-2 cm across, distally 1-1.8 x 0.8-1.4 cm, (but most of this used to have adjacent sheath material: true petiole 3-18 cm), channelled adaxially, convex abaxially, with raised sharp edges, abaxially white-tomentose; rachis 1.1-2 m, in mid-leaf 0.7-2 cm across, abaxially rounded with two blunt wings, adaxially channelled with blunt edges, densely white-tomentose when young; leaflets regular, the leaflets on opposite sides of the rachis at an angle of nearly 180°, stiff in the proximal part, half-pendulous in their more distal part, green or glaucous with waxy covering when fresh, 49-73 on each side of the rachis, the proximal 9.5-59 x 0.1-1.1 cm, median 50-70 x 1.2-2.3 cm (interval 1-2 cm), distal 13.5-42 x 0.3-1.4 cm, ramenta sparse on the abaxial side, on the midrib only, spaced, large, white, main veins 2-4. STAMINATE INFLORESCENCE multiple in (1) 2s-6s, branched to 1-2 orders (in the Isalo populations the rachillae only branched at the very base of the inflorescence, and sometimes ; these branched rachillae not present), erect, 70-110 cm; peduncle 35-64 cm long, proximally 5-7 mm across, distally 3-7 mm across, densely white-puberulous; common prophyll 3.5-13.5 cm and membranous; peduncular bracts 9-24 cm (inserted at about 3 cm from the base of the peduncle), 22-55 cm (inserted at c. 6 cm), 60-105 cm (inserted at about 6 cm), 62-107 cm (inserted at about 12 cm), densely pubescent abaxially, adaxially smooth and glabrous; rachis 21-46 cm long, ± glabrous, with about 30 unbranched and 10 branched first order branches in Andringitra, 0-1 unbranched and 25-52 branched ones in Isalo, with rachis bracts about 15 x 0.3 cm; rachillae close, porrect, 2-12 cm long, 1 mm across, zigzag, especially distally, with dense flowers; pedicel 0.2-1.5 mm. STAMINATE FLOWERS with the calyx connate for 0.3-1 mm, free lobes 0.8-1 x 0.8 mm, triangular, acute; petals free, 7.5-9 x 1.5 mm, gradually tapering to acute apex; anthers 2.5-3.2 x 1.3-1.4 mm, filaments 0.6 -0.7 mm, the 3 epipetalous stamens adnate for 0.7 mm; pistillode 1 x 0.4 mm. PISTILLATE INFLORESCENCE solitary, erect in bud, spreading at anthesis, pendulous in fruit, 66-158 cm long, branching to one order; peduncle 45-105 cm, slightly flattened, proximally 6-10 x 4-10 mm across, distally 4-10 mm across, pale brown- or grey-white tomentose, distally glabrescent; prophyll 6-18 cm, membranous; peduncular bracts respectively 13-34 (inserted at 0-3 cm from the base of the peduncle), 27-48 x 2.2-2.6 (inserted at 0-6 cm), 60-103 (inserted at 6-7 cm) and 59-158 x 1.6-2 cm (inserted at 10-14 cm), the distal two with apices at the same level; all bracts grey-puberulous to white floccose-tomentose abaxially, adaxially glabrous, smooth and rich brown when dry; non-tubular peduncular bract 4-9 x 0.3-0.4 cm; rachis 17-40 cm long, proximally white-tomentose or with grey bloom, otherwise glabrous; most proximal rachis bracts 38 x 5 mm; rachillae spreading or porrect, slightly zigzag, 24-35 in number, 4-26 cm long, 1.2-2 mm across, sinuous, with spaced flowers, with slightly bulbous base 3.5-4 x 2 mm, white-waxy; bracteole 2.3 x 1.8 mm; pedicels 0.5-5 mm. PISTILLATE FLOWERS with the calyx connate for 0.8 mm, free lobes triangular, acute, 1-3 x 1.0-2 mm; petals 6.5-8 x 1.2-1.7 mm, ovate, acute; staminodes 1.8 x 0.6 mm; ovary 2.5 x 1.3 mm. FRUIT yellow, 20-22 x 22-23 mm, 1-seeded; stigmatic remains lateral or subbasal. SEED 16-18 x 18-19 mm, dark brown; seedcoat brown, 0.2 mm thick; embryo 4 mm. EOPHYLL pinnate. (J. Dransfield and H. Beentje. 1995)/Palmweb. The protologue describes populations from the Andringitra, but all collections we have seen are from a later date. The illustration in the Flore de Madagascar (1945) has a habit sketch which is based on a photograph by Humbert 13698, which is a R. xerophila. (J. Dransfield and H. Beentje. 1995)/Palmweb. |
Culture
Truly R. glauca is one of the most promising palms for cultivation Madagascar has to offer. Tolerant of soil, exposure, and water needs, Ravenea glauca is proving itself in a wide range of growing conditions while reliable as a gorgeous mid-sized palm. Perhaps this is due to its natural conditions growing in deeply shaded, yet still hot deep canyons, sometimes very wet and sometimes very dry, and when tall enough, exposed to scorching sun. Few palms are as forgiving and as beautiful at the same time. Because R. glauca, like all Raveneas, is dioecious, growers would do well to assure this palm sets viable seed in cultivation by planting groups separated from other Raveneas. These palms are considered endangered in habitat.
Comments and Curiosities
This is a dioecious genus.
Conservation: Vulnerable. We are uncertain about the status of populations in the Andringitra; no plants of this species have been collected there since 1922. Elsewhere this species is only known from the Isalo, where population size is probably a few hundred.
Uses: Not eaten, since the heart is bitter.
The most curious thing about this palm has already been alluded to above. It not only tolerates such a wide range of conditions and outright abuse, it is remarkably bug and pathogen resistent. And does it all while still looking pampered.
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A variable species, plants can be tall and slender in canyons at Isalo, but they can also flower when almost stemless in a dry river bed. The original description states that this species forms vast forests in the Andringitra mountains, between 1200 and 1800 m, to the exclusion of any other plant; it is said to be resistant to bush fires. Having seen the stands in the Isalo, HB finds monospecific forests without undergrowth hard to believe. The Latin name refers to the glaucous, waxy undersides of the leaflets. (J. Dransfield and H. Beentje. 1995)/Palmweb. This is a tillering palm, it exhibits saxophone style root growth (it has a heel), keep top third of heel above soil elevation! |
- IMAGE GALLERY
Stately individual.
Different form???
Unknown sp. on right.
Habitat - says it all. Madagascar.
Habitat, Madagascar.
Coastal California.
Coastal California.
At Gary Le Vines place. Baking sun, Escondito, California.
At Gary Le Vines place. Escondito, CA. Photo by Troy Donovan.
Old Beach, Tasmania. Garden of Troy Donovan. Photo by Troy Donovan.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
SoCal. Photo by Geoff Stein.
Juvenile
Habitat, Madagascar.
Canyon Habitat, Madagascar.
Ravine bottom, Madagascar.
Gangsta Bob Weas w/ R. glauca, CA!
At Matty Bradford's place. Spring Valley, CA. Photo by Troy Donovan
Isalo, Madagascar. Photo by Dr. John Dransfield, Royal Botanic Gardens, Kew/Palmweb.
Isalo, Madagascar. Photo by Dr. Henk Beentje, Royal Botanic Gardens, Kew/Palmweb.
Isalo, Madagascar. Photo by Dr. Henk Beentje, Royal Botanic Gardens, Kew/Palmweb.
Isalo, Madagascar. Photo by Dr. Henk Beentje, Royal Botanic Gardens, Kew/Palmweb.
Pomona, northern end of the Sunshine Coast region, southeast Queensland, Australia. Garden of Rudy Meyer. Photo by Wal Donovan
In habitat. Photo-Rare Palm Seeds.com
In habitat. Photo-Rare Palm Seeds.com
In habitat. Photo-Rare Palm Seeds.com
Photo: Jungle Music Palms & Cycads.com
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External Links
- Glossary of Palm Terms
- MODERN BOTANICAL LATIN
- "Just To Be Clear"
- http://www.palms.org/principes/1994/ravanea.htm
- THE SAXOPHONE STYLE ROOT GROWTH (HEEL)
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).
Dransfield, J. & Beentje, H. 1995. The Palms of Madagascar. Royal Botanic Gardens, Kew and The International Palm Society.
Many Special Thanks to Ed Vaile for his long hours of tireless editing and numerous contributions.
