Alocasia vs. Colocasia

Taxonomic Diversity

• The genus Alocasia comprises approximately 70 species of tropical herbaceous perennials from rain forests from the Old World. From Southeast Asia to northern Australia, including numerous islands around Malaysia and the Phillippines, Alocasia species grow. Genus Colocasia is much smaller, but taxonomists continue to discuss and analyze species to determine if they truly belong in this group. Six to 10 species, as of 2010, populate Colocasia. They are native to both southeastern Asia and tropical parts of Central or South America.

Rooting Habit

• All members of Colocasia grow from tubers, which are swollen underground stems or roots with an abundance of storage tissues. Alocasia contains mainly species that develop from a rhizome, a horizontal fleshy stem that often branches and stores carbohydrates. Rhizomes grow either underground or at the soil surface. However, some Alocasia species grow from tubers. Smaller roots emanate out from the tubers and rhizomes to anchor the plants and absorb water and nutrients from the surrounding soil.

Foliage Features

• Elephant ears or taro plants produce leaves that look like pointed shields, arrowheads or triangle wedges. Those in the Colocasia have petioles—leaf stems—that attach to the leaf underside rather than the leaf's edge or margin. Such leaves are botanically described as peltate. There usually is a leaf slit from this petiole attachment outward towards the leaf edges. By contrast, Alocasia species may be peltate when tiny and first emerging, but as the leaves grow and reach maturity, the petiole is distinctly attached at or just inside the leaf edge. This petiole attachment to the leaf difference usually creates the visual affect of Colocasia leaves dangling atop their stems, but Alocasia leaves are often held more upright or rigidly on the plant.

Reproduction

• Both Alocasia and Colocasia species reproduce by developing vegetative clones of their tubers or rhizomes underground. Sexually, both also produce a flower that looks like a finger surrounded by a cloak—the spadix and spathe, respectively. Tiny male and female flowers cover the spadix, which are pollinated by insects or food-seeking animals. The tiny fruits that may ensue are fleshy berries with seed inside. Alocasia berries are red or orange. Colocasia berries are glossy green.