Family : Araceae
Text © Pietro Puccio
English translation by Mario Beltramini
The Alocasia macrorrhizos (L.) G.Don (1839) is native to the Bismarck Archipelago, Borneo, Philippines, Solomon Islands, Peninsular Malaysia, Papua New Guinea and Queensland.
The name of the genus comes from the name of another genus of the same family: Colocasia; the name of the species is the combination of the Greek words “makros” = big, and “rhiza” = root, with obvious meaning.
Common names: “Australian cabbage”, “biga”, “creek lily”, “cunjevoi”, “giant alocasia”, “giant elephant’s ears”, “giant taro”, “upright elephant ear” (English); “alocasie”, “alocasie à grandes racines”, “alocasie à grosse racine” (French); “alocasia”, “orecchio di elefante” (Italian); “alocásia”, “inhame-açú”, “orelha de elefante gigante”, “taiá rio branco, “taioba” (Portuguese); “hoja de pato”, “pato”, “malanga” (Spanish); “Alokasie” (German).
Rhizomatous, evergreen herbaceous with stem, partly underground, which in the old plants can reach the height of 2 m, with a diameter up to about 20 cm; petioles long up to 1,5 m and leaves cordate-ovate, long up to 1 m and 90 cm broad, almost erect, with the edges slightly undulated, of an intense glossy green colour.
Inflorescence formed by a yellowish white spathe, 15-30 cm long and about 5 cm broad, enclosed and tubular at the base for about 4 cm, and by an about 10-30 cm long spadix with the female flowers occupying the lower part for about 2 cm of length, separated by a sterile zone of about 1 cm from the male ones, distributed over a length of about 7 cm and ending in a sterile appendix of bronze colour and 7-20 cm long.
The flowers are protogynous (the female flowers are receptive before the ripening of the male ones, thus avoiding self-fertilization); the pollination happens thanks to insects attracted by the smell emitted by the spadix and by the simultaneous increase of temperature. This, which concerns the male part of the spadix, and even more the sterile appendix, lasts about 40 hours, with an increase of temperature of 10-20°C, with respect to the local one.
The fruits are ovoid berries, of a bright red colour when ripe, about 1 cm long. It reproduces by seed, rhizomes division and portions of stem.
Impressive plant which can be cultivated in full sun in the tropical and humid subtropical zones or in partial shade; it can be cultivated in temperate areas, where, on the contrary, it tends to lose the leaves in winter, even if it can resist, at rhizome level, provided well mulched, to temperatures around -8/-9°C.
It is not particularly demanding about soil, which must be kept constantly humid during the vegetative time. It can be cultivated in pot in porous substrata, draining and rich of organic substance, for the decoration of vast and luminous spaces, with temperatures over the 12-14°C, in order to avoid leaf damage.
At times, the rhizome and the stem are utilized, in the zones of origin, for animal consumption and, time ago, during famine periods, also for human alimentation, provided cooked previously for long time, in order to eliminate the toxic substances contained, in particular the calcium oxalate, which can cause serious reactions if chewed and ingested when raw; even the contact with the sap can cause allergic reactions.
The leaves, when broken, emit a smell of bitter almonds due to the presence of Prussic acid (cyanide), about 30 mg of HCN/kg, which is also present, in less extent, in the stem.Synonyms: Arum macrorrhizon L. (1753); Arum indicum Lour. (1790); Colocasia macrorrhizos (L.) Schott & Endl. (1832); Alocasia macrorrhizos (L.) Schott (1832); Calla maxima Blanco (1837); Alocasia macrorrhiza (L.) G. Don (1839); Colocasia indica (Lour.) Kunth (1841); Philodendron peregrinum (L.) Kunth (1841); Alocasia indica (Lour.) Spach (1846); Alocasia macrorrhiza (L.) Schott (1852); Alocasia indica (Lour.) Schott (1854); Alocasia metallica Schott (1854); Alocasia indica var. metallica (Schott) Schott (1860); Alocasia plumbea Van Houtte (1875); Alocasia indica var. heterophylla (1879); Alocasia indica var. variegata (K.Koch & C.D.Bouché) Engl. (1879); Alocasia grandis N.E. Br. (1886); Alocasia indica var. diversifolia Engl. (1920); Alocasia indica var. rubra (Hassk.) Engl. (1920); Alocasia indica var. typica Engl. (1920).