Amorphophallus pendulus: The Pendulous Aroid with Silver-Veined Leaves of Borneo
Among the most visually distinctive members of its genus, Amorphophallus pendulus Bogner & Mayo combines two characters found nowhere else in the entire group: a long, pendulous, whip-like appendix and leaves with deep velvety green leaflets marked by vivid, feathered silver variegation along the midrib. Bogner and Mayo formally described it in 1985 in the journal Aroideana. Originally documented only from East Malaysia (Sarawak), it also occurs in the forests of northern and western Kalimantan. Growing in the damp understory of sandstone hills, this species appeals equally to botanists, collectors, and those seeking something genuinely extraordinary in the aroid world.
Taxonomic Identity of Amorphophallus pendulus
Amorphophallus pendulus belongs to the family Araceae. Bogner & Mayo described it in Aroideana 8 (1) (1985): 19–21. No synonyms are currently recognized for this species.
Morphological Description Amorphophallus pendulus
Tuber and Leaf Amorphophallus pendulus
The tuber of Amorphophallus pendulus is subglobose, reaching up to approximately 18 cm in diameter. It produces no offset structures. The plant bears a single solitary leaf. The petiole reaches up to 90 cm in length — and probably longer in mature plants — and approximately 1.5 cm in diameter. Its surface is smooth, with a reddish or blackish-green background carrying numerous pale green and/or dark green spots. Rarely, the petiole is entirely green.
The lamina is highly dissected, up to about 80 cm in diameter. The rachises carry narrow wings only in the distal parts. Leaflets are narrowly elongate-elliptic, 7–20 cm long and 2–5 cm wide. They are acuminate at the apex. The upper surface is deep velvety green with feathered silver variegation along the midrib. More rarely, the upper surface is entirely green or flushed with reddish-purple. Seedling leaves are entirely reddish-purple. This leaflet pattern — velvety green with bright silvery midrib feathering — is unique in the genus and provides an immediate identification character even outside the flowering season.
Inflorescence and Peduncle Amorphophallus pendulus
The inflorescence of Amorphophallus pendulus is solitary and long-peduncled. The peduncle reaches 20–80 cm in length and approximately 0.5–2 cm in diameter. Its coloration matches the petiole.
Spathe Amorphophallus pendulus
The spathe is elongate-elliptic and somewhat linguiform, 15–32 cm long and 6–13 cm in diameter. It is acute at the apex, with a convolute, tubular base. The limb is obliquely erect and somewhat hooded over the spadix. The outer limb surface is dark to blackish-purple, with approximately circular, pale green spots that are sometimes confluent. These spots appear more densely arranged near the base. The inner limb surface is dark dull violet-purple, with or without small pale green spots near the margin. The innermost basal portion carries scattered small blackish warts. Above this wart zone follows a broad, deep wine-red zone, then a narrow pale purplish zone toward the top.
Spadix and Floral Zones
The spadix of Amorphophallus pendulus greatly exceeds the spathe in length, measuring 27–67 cm in total. The female part is cylindric to slightly conic, 1.5–3 cm long and 0.6–1.5 cm in diameter. The base is strongly oblique. Flowers are congested to slightly distant, especially in the upper portion. The male part is cylindric to slightly conic, 2.5–7.5 cm long and 0.6–1 cm in diameter. Flowers are congested or slightly distant in some parts, and sometimes align in longitudinal rows.
The appendix is myosuroid (whip-like) and pendulous — the defining character of this species. It measures 20–60 cm in length and only 0.4–1 cm in diameter at the base. It is acute at the apex. Its base is contiguous with the male zone or slightly constricted from it. The lower portion of the appendix is covered with shortly elongate staminodes or is smooth. The rest of the appendix surface is rugulose and ± ridged. The color is dirty whitish, pale yellow, or deep dull purplish. This extraordinarily long, pendulous, thread-like appendix hanging freely below the spathe gives the species both its name and its most spectacular visual feature.
Female Flowers
Each ovary is globose, approximately 2 mm in diameter and 2 mm tall. Its color is pinkish, purplish, or blackish. Each ovary is 2–3-locular, with one basal ovule per locule. The style is nearly absent, approximately 0.2 mm long and about 1 mm in diameter. The stigma is large, shallowly to strongly 2–3(–4)-lobed, 2–3 mm in diameter and approximately 1.5 mm tall. Lobes are rounded or conical and acute. The surface is scabrate.
Male Flowers
Each male flower carries 3–4 stamens, sometimes strongly deformed through excessive acro-basal elongation. Stamens are 0.8–1 mm long. Filaments are 0.4–0.5 mm long and partly connate. Anthers are 0.4–0.5 mm long and approximately 0.6 mm in diameter, truncate, and yellowish or dull pinkish. Pores are apical.
Fruit and Seed
The infructescence fruiting part reaches up to about 20 cm long and 1.5 cm in diameter. Berries are globose to depressed-globose, 9–12 mm in diameter, 8–9 mm long, and orange-red. Seeds are subglobose to unilaterally depressed, 7–8 mm in diameter, with a very deep short groove or deep or shallow depression. The seed coat is minutely rugulose and ivory white.
Distribution of Amorphophallus pendulus
Amorphophallus pendulus originally appeared in botanical records only from East Malaysia (Sarawak). Subsequently, several field expeditions throughout the forests of northern and western Kalimantan, Indonesia, also documented the species there. Its range therefore spans both the Malaysian and Indonesian portions of Borneo.
For verified occurrence data and georeferenced records, refer to GBIF – Amorphophallus pendulus and the Plants of the World Online (POWO) – Kew.
Habitat
This species grows in somewhat open primary forest, specifically in damp and shady places on sandstone substrates. It occurs at elevations between 400 and 800 m above sea level. Its dependence on sandstone soils in primary forest understory conditions makes it one of the more ecologically specialized members of the genus.
Taxonomic Notes
Amorphophallus pendulus is an exceptionally attractive species. Two features make it uniquely identifiable within the entire genus. First, the very long, pendulous, myosuroid appendix — hanging freely and thread-like below the spathe opening — appears in no other Amorphophallus species. Second, the leaflet coloration pattern — deep velvety green with feathered bright silver variegation running along the midrib — also has no parallel in any congener. Together, these two characters make A. pendulus instantly recognizable whether in leaf or in flower, a rare quality among aroids that often require the inflorescence for identification.
Photo Reference
References
- Bogner, J. & Mayo, S.J. (1985). Amorphophallus pendulus Bogner & Mayo. In: Aroideana 8 (1): 19–21.
- Kew Science. Amorphophallus pendulus Bogner & Mayo – Plants of the World Online. Available at: https://powo.science.kew.org/taxon/968076-1
- GBIF Secretariat. Amorphophallus pendulus occurrence data. Global Biodiversity Information Facility. Available at: https://www.gbif.org/
