Alocasia macrorrhizos
Common Name: giant elephant's ear 
Type: Bulb
Family: Araceae
Native Range: Australia, Malesia, Papuasia
Zone: 9 to 11
Height: 12.00 to 15.00 feet
Spread: 6.00 to 8.00 feet
Bloom Time: Seasonal bloomer
Bloom Description: Greenish-white
Sun: Part shade
Water: Medium to wet
Maintenance: Medium
Suggested Use: Annual
Flower: Showy
Leaf: Evergreen
Fruit: Showy
Other: Winter Interest
Tolerate: Wet Soil

Culture

Winter hardy to USDA Zones 9-11 where plants are best grown in part shade or filtered sun in moist to wet, organically rich soils in sheltered locations protected from strong winds which can seriously damage the huge ornamental leaves. Leaves often scorch when exposed to full sun. Plants will grow in periodically flooded areas. Petioles weaken and are unable to support the leaves in too much shade.

Where not winter hardy, rhizomes may be started indoors in early spring in pots or containers. After last spring frost date, containers/pots may be sunk to the rim in the garden or set out on a patio. Plants require regular watering and fertilization. Before first fall frost, pots and containers should be brought inside where they can be overwintered in sunny, humid but cool (around 60-65 degrees F) locations. Reduce watering in winter. Return plants to the garden in spring. Propagate by reddish seeds which develop on the spadix in a manner reminiscent of corn on the cob.

Plants grow rapidly and may be grown as annuals in USDA Zones 4-8.

Noteworthy Characteristics

Alocasia macrorrhizos, commonly called giant taro or upright elephant ears, is a rhizomatous tropical perennial of the arum family that is treasured both for its giant ornamentally decorative leaves which resemble the ears of an elephant and its edible rhizomes which have been cultivated for many years in the tropics as an edible vegetable under the common name of taro. This is a forest understory plant that has widely naturalized over large tropical areas extending from India to Southeast Asia to Malayasia, however it is unclear as to the specific geographic regions where this plant was originally native. It is closely related to Colocasia, except for the position of the leaves (upright Alocasia leaves point skyward on rigid stems whereas drooping Colocasia leaves point toward the ground).

Thick, cordate, prominently-veined, wavy-edged green leaves (to 3-6’ long and 3-4’ wide) are borne on rigid stalks (long-sheathed petioles) which emerge from a stout upright trunk (becoming woody with age) which can eventually grow to as much as 6’ tall. The entire plant can eventually grow to as much as 12-15’ tall in optimum growing conditions with a spread to 6-10’ wide.

Greenish spathe and spadix (Jack-in-the pulpit type) stand 8-10” tall (flowers are packed into the spadix and surrounded by the spathe). Flowers are not particularly showy. . Flowers bloom intermittently throughout the year. Flowers are followed by red berry-like fruits which are infrequently formed in cultivation.

Notwithstanding its ornamental features, this giant taro is also an edible root vegetable. It has been harvested for many years in the tropics as a potato-like substitute in areas where potatoes will not grow. Stem pith is also edible. Rhizomes and stems must first be cooked (usually boiled) prior to eating in order to remove calcium oxalates which render uncooked rhizomes and stems inedible. Stem pith is typically boiled, and then dried and ground into flour.

Genus name comes from the Greek words a meaning without and Colocasia the name of a closely allied genus, from which it was separated.

Specific epithet comes from the Greek words macro meaning large and rrhiza meaning root in reference to plant rhizomes.

Alocasia is similar to but not identical to Colocasia.

Problems

Watch for spider mites, scale, mealy bugs and aphids.

Garden Uses

Bold foliage plant for frost-free areas in part shade. In areas where not winter hardy, plants may be grown in containers that are overwintered indoors. Also may be grown as a houseplant (best in sun room or hothouse). Plants grown indoors need high humidity.