Elephant ear

Identification and origin

Colocasia esculenta belongs to the arum family, Araceae. Its native range runs from the Indian subcontinent (India, Bangladesh, Nepal, the eastern Himalaya and Assam) through Myanmar, Thailand, Laos, the Malay Peninsula and Sumatra to southern and southeastern China and Taiwan. Cultivated for thousands of years in Asia and Polynesia, it has naturalized in many warm, wet regions and is even considered invasive in some wetlands with mild climates.

It is a frost-tender herbaceous perennial that forms a clump from an underground corm. That lumpy corm, with brown skin and white or pinkish flesh, is a staple food in the tropics. The species name esculenta in fact means “edible.”

It is grown mainly for its foliage. The heart- to arrow-shaped leaves, with prominent veins, can exceed 2 ft in length and are held on stalks about 3.5 ft long. The stalk attaches to the underside of the blade, a little in from the notch (a peltate leaf), and the leaves hang slightly downward: that is the easiest way to tell it from Alocasia, whose leaves point upward. In cultivation the plant usually grows 3–6 ft tall and about as wide. It rarely blooms: the inflorescence, a white or yellow spadix surrounded by a yellowish or greenish spathe, often stays hidden beneath the leaves.

Among more than two hundred cultivars are ‘Black Magic’, with dusky purple-black matte leaves; ‘Black Coral’, with glossy black leaves; ‘Illustris’, with near-black blades and bright green veins; ‘Mojito’, speckled with black; ‘Fontanesii’, with violet stalks; and ‘Pink China’, regarded as one of the most cold-tolerant.

Light

Outdoors, elephant ear grows best in part shade or filtered sun, but it tolerates full sun as long as it never runs short of water. Dark-leaved cultivars develop their best color in sun. Choose a spot sheltered from strong winds, which shred the large leaves.

Indoors or in a greenhouse, give it bright, indirect light.

Watering

This is a thirsty plant: the potting mix should never dry out while it is growing. Check the root ball with a finger and water as soon as the surface starts to lose its moisture. Elephant ear tolerates almost boggy soil and can even grow at the edge of a pond, with the root ball sitting in shallow standing water, as long as the leaves stay above the surface.

It is also a heavy feeder: apply a balanced liquid fertilizer at least once a month during growth, or more often if you want very large leaves. In winter, if the plant keeps growing indoors, keep the mix just barely moist. A semi-dormant plant should be kept drier, and a dormant corm must stay dry.

Potting mix

It needs soil rich in organic matter, constantly moist but not airless: a loam or clay soil suits it. The ideal pH is slightly acidic to neutral, around 5.5 to 6.5. In a container, use a good peat-free potting mix enriched with compost, in a heavy, stable pot at least 18 in wide and deep, because the plant becomes large and top-heavy with foliage.

Temperature

Elephant ear loves heat and humid air. It grows best between 77 °F and 84 °F and only stays evergreen above about 70 °F. It struggles as soon as temperatures stay below 50 °F for long periods. Frost kills the foliage.

In the ground it is grown in USDA zones 8a to 11b; in the coldest parts of that range, mulch the planting site heavily in fall to protect the corm. Elsewhere you have two options: bring the potted plant indoors before nights drop toward 39 °F, or store the dormant corm. In that case, after the first frost, cut off the foliage, dig up the corm, let it dry for several days, then store it in an open container, lightly covered with dry peat moss or wood shavings, in a cool place between 45 °F and 55 °F, never letting it freeze.

Repotting

In spring, start the corms indoors in a warm spot, with the top of the corm just at the surface of the mix: the first leaves take a few weeks to appear. Move plants outside or into the ground only after the last frost, once the weather has warmed. A plant kept in a pot year-round is repotted at the start of the growing season into a slightly larger container with fresh, rich mix.

Pruning

No pruning is needed. Throughout the season the plant keeps producing new leaves while the oldest ones yellow: cut those off at the base to keep the clump tidy. To overwinter an actively growing plant indoors, you can keep just the two youngest leaves.

Propagation

Division is the easiest method. During dormancy, separate the small side corms that form around the main corm, or cut a clump into divisions that each have a bud and roots. Replant them in a warm spot in moist mix.

Seed is possible, but you get a large plant far sooner from a big corm. Taro corms sold in Asian grocery stores can also be planted, provided they have not been treated to prevent sprouting.

Common problems

• Slow growth, small leaves: not enough heat, water or fertilizer, or a pot that is too small.
• Plant sulking in early summer: temperatures still too cool; it will take off once the heat arrives.
• Leaves yellowing, then drying out: normal turnover of old leaves, a cold snap, mix that dried out, or the plant going dormant at the end of the season.
• Torn leaves: exposure to wind.
• Corm rotting over winter: storage too damp or too cold.
• Pests: indoors and in greenhouses, watch for spider mites, aphids and whiteflies. Outdoors it has few enemies, and deer and rabbits tend to leave it alone.

One symptom can have several causes: always check temperature, moisture in the mix, light and the condition of the roots together.

Toxicity

All parts of the raw plant are toxic to dogs, cats and horses, and to people. They contain insoluble calcium oxalate crystals that cause immediate, painful irritation of the mouth, swelling of the lips and tongue, heavy drooling, difficulty swallowing and vomiting. The sap can also irritate skin and eyes, so wear gloves when handling the plant. The corm and leaves become edible only after thorough cooking. If a pet or person eats any part of the plant, contact a veterinarian or a poison control center.