Alocasia macrorrhizos (elephant ear taro)

Elephant ear taro is a massive herb, forming a thick erect trunk in large plants and reaching four metres in height. The leaves are held erect, with petioles (leaf stalks) up to 130 cm long. The leaves are stout, with sheathing in the lower part. The leaf blades are arrow-shaped, bluntly triangular in general outline with somewhat rounded basal lobes. There are about nine main veins, diverging at an angle of about 60 degrees.

The inflorescences (flower stalks) occur in pairs amongst the leaf bases, preceded by a cataphyll (scale leaf). The spathe (floral bract) is about 13 to 35 cm long, constricted about 1/6 of the way from the base, with the lower part folded into a green tube. The limb is oblong, pale yellow, cowl-like when in flower, then bending back and deciduous. The spadix (flower spike) is slightly shorter than the spathe. The lowermost 1 to 2 cm of the spadix is female and covered with about 30 pistils (female parts). Each pistil consists of a pale green ovary with a yellow 3 to 5 -lobed stigma sitting directly on it. Above the female flowers there is a zone with about four whorls of white sterile organs corresponding in position to the spathe constriction. The next floral zone is male, covered with tightly packed white rhomboid to hexagonal male flowers. At the tip of the spadix is a yellowish appendix, which is at least half the spadix length and covered with tiny irregular furrows.

The fruit is a few-seeded red berry, which when ripe is exposed by the recurving segments of the lower spathe tube, which detaches on maturity. Each berry has several pale brown seeds about 4 mm in diameter.

Alocasia macrorrhizos is used medicinally. For example, in Hawaii, it has been used to treat digestive complaints, as a topical dressing for burns, and as a love charm. In the Philippines, the leaf stalks have been used to relieve toothache and on Java the roots and leaves have been used to relieve pain and redness. The rhizomes contain an anti-fungal protein called alocasin.

Today, Alocasia macrorrhizos is a popular ornamental plant grown for its large foliage and striking aroid inflorescences. It has also shown promise in sewerage treatment, as it grows rapidly in wetland conditions and has a propensity to accumulate metal contaminants such as zinc.