Amorphophallus is a large genus of approximately 200–245 tropical and subtropical herbaceous perennials in the arum family (Araceae), subfamily Aroideae, tribe Thomsonieae. The genus was formally described in 1834 from a publication by Joseph Decaisne, based on work by Dutch botanist Carl Ludwig Blume (Amorphophallus Blume ex Decne., Nouv. Ann. Mus. Hist. Nat. 3: 366).
All species grow from subterranean corms or tubers that range dramatically in size — from a modest 10 grams in the diminutive A. pusillus to a record-breaking 139 kilograms in A. titanum. Each plant typically produces a single, large compound leaf atop a patterned, trunk-like petiole. In most species the inflorescence emerges before or independently of the leaf. The inflorescence consists of a spathe (a large sheathing bract) enclosing a central spadix; flowers are monoecious with female flowers at the base, male flowers above, and a sterile appendix of staminodes at the apex. Fruit are soft fleshy berries produced in a range of colors.
The genus has a pantropical Old World distribution, spanning Africa, tropical Asia, Australasia, and Pacific islands but entirely absent from the Americas. Plants typically occupy lowland disturbed habitats, forest margins, and secondary forests. Most species have narrow endemic ranges. Several species contain calcium oxalate crystals that make them toxic when consumed raw; thorough cooking or drying neutralizes the irritants, and a number of species have been used as food crops or famine foods for millennia.
Etymology
The name Amorphophallus is constructed from two Ancient Greek roots: amorphos (without form, misshapen) and phallos (penis). Together they allude to the prominent, often contorted or oddly shaped spadix that characterizes the genus's inflorescence. The name was coined in the context of the 1834 formal description published by Decaisne, building on Blume's earlier work.
Distribution
Amorphophallus has a pantropical Old World distribution. The genus is native across sub-Saharan Africa (including Madagascar) — with records from Angola, Cameroon, DR Congo, Ethiopia, Ghana, Kenya, Madagascar, Mozambique, Nigeria, Tanzania, Uganda, and Zimbabwe among many others — and throughout tropical and subtropical Asia, from the Indian subcontinent (India, Nepal, Sri Lanka, Bangladesh) and the Andaman and Nicobar Islands east through Southeast Asia (Myanmar, Thailand, Laos, Cambodia, Vietnam, Malaysia, the Philippines, and the Indonesian archipelago including Jawa, Sumatera, Sulawesi, and Maluku), reaching Japan, Taiwan, Hainan, and south into Queensland and Western Australia in Australasia. The genus is absent from the Americas.
Numerous species have been introduced beyond their native ranges; introductions are recorded in Fiji, New Caledonia, Vanuatu, Samoa, the Society Islands, the Marquesas, the Cook Islands, the Comoros, the Seychelles, and Trinidad-Tobago, reflecting the movement of economically useful species such as A. konjac and A. paeoniifolius through human cultivation. The distribution data derives from the World Checklist of Vascular Plants (WCVP) as aggregated by GBIF.
Taxonomy
Amorphophallus Blume ex Decne. (Araceae: Aroideae: Thomsonieae) was published in Nouv. Ann. Mus. Hist. Nat. 3: 366 (1834). The type species is Amorphophallus campanulatus (Decne.). Four subgenera are currently recognized: Amorphophallus, Scutrandrium, Metandrium, and Afrophallus.
Eighteen genus-level names are now treated as synonyms, including historically used segregate genera such as Hydrosme Schott, Conophallus Schott, Pythonium Schott, Pseudodracontium N.E.Br., Thomsonia Wall., and Candarum Schott, among others. The consolidation of these segregate genera into a single broad Amorphophallus reflects modern phylogenetic reassessment of the tribe Thomsonieae.
Ecology
Species of Amorphophallus typically inhabit lowland disturbed grounds, forest margins, and secondary forests within their tropical and subtropical range. The vast majority of species have narrow endemic distributions. The inflorescence of many species produces heat (thermogenesis) and, in the most famous members, a powerful odor mimicking decomposing flesh — a pollination strategy attracting carrion beetles and blow flies. All parts of the plant contain calcium oxalate crystals, which cause intense irritation to mucous membranes if the raw plant is ingested or handled extensively. Caterpillars of the moth species Palpifer sexnotatus and P. sordida are known to feed on the foliage.
Cultivation
Amorphophallus species are frost-tender and best suited to USDA hardiness zones 7b–11a (with A. konjac extending to zone 6 with protection). In temperate climates they require container growing or corm storage indoors over winter. Plants prefer dappled to partial shade (2–6 hours of direct sun), rich organic soil with excellent drainage, and consistent moisture during the growing season. They are heavy feeders and benefit from regular fertilization while in active growth. As temperatures drop in autumn the leaf naturally dies back; at this point corms should be lifted and stored dry in a cool, frost-free location until the following spring.
Common problems include mealybug infestations, collar rot caused by Sclerotium rolfsii, damping-off in seedlings, and corm rot resulting from overwatering or poorly drained soil. The optimal active-growth temperature range is approximately 20–25°C (68–77°F).
Propagation
Amorphophallus can be propagated by three main methods. Division of cormlets (offset corms) from the parent tuber is the most reliable and fastest route to blooming-size plants. Several species also produce aerial bulbils along the petiole or leaf rachis; these can be detached and grown on. Seed propagation is possible but slower: seeds require warm, consistently moist conditions (approximately 24°C) and may take between one and eight months to germinate. Seedlings typically need several growing seasons before they reach flowering size.
Cultural Uses
Several Amorphophallus species have significant food and medicinal value across their native range. A. konjac (konjac or devil's tongue) is cultivated extensively in East Asia for its corm, which is processed into glucomannan-rich flour. This flour is used to make konnyaku (a firm Japanese jelly), shirataki noodles, and various dietary supplements; glucomannan's high water-absorbing capacity is also exploited for constipation relief and cholesterol management. A. paeoniifolius (elephant foot yam) is an important food crop throughout the Indo-Pacific, its large corms eaten as a vegetable after cooking. Numerous additional species function as famine foods in Africa and Asia, consumed after thorough boiling or roasting to neutralize the calcium oxalate crystals.
Traditional medicinal applications vary by culture and species: flowers of some species have been used to reduce fever, roots to assist childbirth, and glucomannan preparations for digestive ailments.
