Amorphophallus paeoniifolius: The Elephant Foot Yam of Southeast Asia
Few aroids combine scientific fascination, culinary significance, and sheer visual drama as effectively as Amorphophallus paeoniifolius (Dennst.) Nicolson. Nicolson formally placed it under the genus Amorphophallus in Taxon 26 (1977): 338. Its range spans from Madagascar eastward through India, Malesia, Thailand, Indochina, southern China, Polynesia, and northern Australia — making it one of the most geographically widespread aroids in the world. Javanese farmers cultivate two distinct forms under the local names walur and suweg, the latter valued for its edible and glucomannan-rich tubers. Its broadly campanulate spathe, massive conical appendix, and characteristically rotting-meat scent make A. paeoniifolius unmistakable — and impossible to ignore — whenever it flowers.
Taxonomic Identity of Amorphophallus paeoniifolius
Amorphophallus paeoniifolius belongs to the family Araceae. Nicolson described it in Taxon 26 (1977): 338. The species carries a large number of synonyms, reflecting its long history of independent collection and naming across its wide range:
- Amorphophallus campanulatus Decne.
- Amorphophallus campanulatus var. blumei Prain
- Amorphophallus campanulatus f. Darnleyensis F.M. Bailey
- Amorphophallus decurrens (Blanco) Kunth
- Amorphophallus malaccensis Ridl.
- Amorphophallus paeoniifolius var. campanulatus (Decne.) Sivad.
- Amorphophallus rex Prain
- Amorphophallus rex Prain ex Hook.f.
- Amorphophallus sativus Blume
- Amorphophallus virosus N.E. Br.
- Arum campanulatum Roxb. [illegitimate]
- Arum decurrens Blanco
- Conophallus giganteus Schott ex Miq. [illegitimate]
- Conophallus sativus (Blume) Schott
- Plesmonium nobile Schott
In Java, two common names exist for the species: walur and suweg. Walur refers to the weedy form with very rough petioles, whose tubers are inedible. Suweg refers to the cultivated form with a nearly smooth petiole, grown for its edible tubers. Taxonomic separation of cultivated from weedy material has proven impossible despite multiple attempts, and ICBN-based names for weedy forms are therefore rejected. Researchers advise identifying cultivars and naming them accordingly, but not as formal taxa.
Morphological Description
Tuber and Leaf
The tuber of Amorphophallus paeoniifolius is depressed-globose, reaching up to 30 cm in diameter and 20 cm in height. It weighs up to approximately 15 kg. The outer surface is dark brown, with prominent and annulate root scars. The tuber produces offsets every season. These offsets are thick, rhizomatous, up to 10 cm long and 4 cm in diameter. The plant bears a solitary leaf, rarely two or more together.
The petiole reaches up to about 2 m in length and approximately 20 cm in diameter. Its background color ranges from pale to dark green or blackish-green, usually with both large and small pale blotches. Larger blotches are often confluent, especially near the base. The surface is shallowly corrugate to strongly echinate-verrucate. The lamina is highly dissected, reaching up to about 3 m in diameter. Its rachises are narrowly or broadly winged almost to the base. Leaflets are variable in shape: rounded, oval, ovate, obovate, elliptic, elongate-elliptic, or elliptic-oblong, acuminate, 3–35 cm long and 2–12 cm in diameter. The upper surface is mid-green, and the lower surface is mid-green or pale green.
Inflorescence and Peduncle
The inflorescence of Amorphophallus paeoniifolius is short-peduncled. The peduncle measures 3–20 cm long and 1–8 cm in diameter. It is usually paler and smoother than the petiole.
Spathe
The spathe is campanulate and broader than long, measuring 10–45 cm long and 15–60 cm in diameter. The base and limb are often separated by a shallow constriction. The limb is spreading and strongly undulate. The outer base surface color is highly variable, ranging from pale green to dark brown. It usually carries large and small, circular, paler spots. The base inside lower part is deep maroon. The upper zone is dirty whitish or very pale pinkish. The outer limb surface matches the base but carries more prominent maroon flushes, especially near the margin. The inner limb surface is usually glossy dark maroon. The base within carries dense verrucae that are variable in form, mostly conical and fleshy.
Spadix and Floral Zones
The spadix of Amorphophallus paeoniifolius is sessile. It is shorter than, equal to, or longer than the spathe, measuring 7–70 cm in length. The female zone is cylindric, 3–25 cm long and 1–12 cm in diameter. Its flowers are congested or slightly distant. The male zone is cylindric to strongly obconic, 2.5–15 cm long. At the base it measures 1–10 cm in diameter; at the top up to 20 cm. Flowers in the male zone are congested.
The appendix is very variable in size and form. It is inflated, measuring 1.5–30 cm long and 1.2–30 cm in diameter slightly above the base. Shapes include globose, depressed-globose, oval, or triangular-conic (pyramidal). The surface is smooth or carries various folds and/or irregular shallow depressions. The base often carries flattened staminodial structures. The apex is obtuse or acutish, and the surface is minutely granulate and glossy dark maroon, rarely pinkish or yellow. Notably, the appendix produces a strong odor resembling rotting meat.
Female Flowers
Each ovary is depressed and circular in cross-section, 3–5 mm in diameter and 1.5–2.5 mm tall. It is entirely pale green or largely maroon with a whitish base. The style is slender, 3–15 mm long, and maroon. The stigma is large, oval or triangular in cross-section, 4–7 mm in diameter and 3–5 mm tall. It is often strongly laterally compressed, then cordate in longitudinal section. It is shallowly to deeply 2- or 3-lobed, with rounded to conic lobes. The lobes sometimes carry a strong groove on their outward-facing side. The surface is verruculate, pale or deep yellow.
Male Flowers
Each male flower carries 4–6 stamens. Stamens reach 4–6 mm in length. Filaments are approximately 0.5 mm long and connate. Anthers are cylindric, 3.5–5.5 mm long and approximately 1.5 mm in diameter, subtruncate, and off-white.
Fruit
The infructescence is long-peduncled. After fertilisation, the peduncle stretches strongly, reaching 20–100 cm. It turns uniformly tan in color and develops myriads of narrow transversal cracks. Berries are closely set to slightly distant, elongate, and ripen from green through yellow to bright red. Mature berries measure 1.5–2 cm long and 8–10 mm in diameter.
Distribution of Amorphophallus paeoniifolius
Amorphophallus paeoniifolius occurs from Madagascar eastward through India to Malesia, Thailand, Indochina, southern China, Polynesia, and northern Australia. This extraordinarily wide range makes it one of the most extensively distributed aroid species on earth. However, much of its present-day distribution likely results from centuries of cultivation and subsequent naturalization rather than natural dispersal. Consequently, determining its original native range remains scientifically complex.
For verified occurrence data and georeferenced records, refer to GBIF – Amorphophallus paeoniifolius and the Plants of the World Online (POWO) – Kew.
Habitat
This species grows in secondary forest, forest edges, teak forests, village groves, thickets, and highly disturbed areas. It tolerates both partial shade and fully exposed sites. It grows up to approximately 800 m altitude. Its adaptability to heavily disturbed habitats helps explain its successful spread across Southeast Asia and the Pacific.
Taxonomic Notes
Amorphophallus paeoniifolius is easy to recognize in flower by two characters acting together. First, the spathe is broadly campanulate and sessile. Second, the appendix is huge, heavily wrinkled, and conical in form. These two features together distinguish it from all other Indonesian congeners. For comparison with A. hirsutus, which shares a similar inflorescence shape, see the notes under that species.
The species carries a long history of cultivation. It has likely escaped and naturalized across much of its present range, making strict separation of wild and cultivated material botanically impossible. Furthermore, the two Javanese cultivar groups — walur (weedy, rough-petiole, inedible) and suweg (smooth-petiole, edible, cultivated) — represent agronomically distinct forms. Javanese people remove oxalate crystals from the tubers through traditional treatments: slicing and sun-drying for several days, or soaking in saline water before cooking. Additionally, A. paeoniifolius is a common species in Java and widely cultivated in Central and East Java for its edible tubers.
Photo Reference
References
- Nicolson, D.H. (1977). Amorphophallus paeoniifolius (Dennst.) Nicolson. In: Taxon 26: 338.
- Backer, C.A. & Bakhuizen van den Brink, R.C. (1968). Flora of Java Vol. 3. Wolters-Noordhoff, Groningen.
- Hetterscheid, W.L.A. & Ittenbach, S. (1996). Everything you always wanted to know about Amorphophallus, but were afraid to stick your nose into! Aroideana 19: 7–131.
- Kew Science. Amorphophallus paeoniifolius (Dennst.) Nicolson – Plants of the World Online. Available at: https://powo.science.kew.org/
- GBIF Secretariat. Amorphophallus paeoniifolius occurrence data. Global Biodiversity Information Facility. Available at: https://www.gbif.org/
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