Colocasia 'Black Stem'
BLACK STEM ELEPHANT EAR
Pronounced: kol-oh-KAY-see-uh es-kew-LEN-tuh
Sunset zones 12, 16-24, H1, H2.
USDA zones: 8-11.
Heat zones: 12-10.
Height: 5-6 feet (1.5-2 m).
Width: 3 feet (90 cm).
The calla lily like flowers have a yellow spathe surrounding a yellow spadix.
Large (2-3 feet), arrow-shaped, glossy, green leaves top deep purple, succulent stalks.
Full sun to partial shade.
Moist to wet, fertile, humus rich soil.
Divide in early spring or late winter.
Prune off dead leaves throughout the growing season to keep the plant looking good.
Pests and Diseases:
Aphids and white flies can be a problem when wintering plants over in the greenhouse.
Rainy Side Notes
Its common name, black stem elephant ear, is all about the plant's dark purple stems so dark they appear to be black. Colocasias are often called elephant ears; however, when I lived in Hawaii we knew these evergreen, big leaf plants as taro. Grown as a vegetable food, taro must be cooked or steeped in water to remove the toxic calcium oxalate before it's eaten. For many people, including myself, unless they ate poi (made from the taro plant) as a staple food when they were children, they don't care for the bland, starchy taste.
The tubers are hardy in USDA zones 8-11, yet Sunset's Western Garden book does not rate them hardy in the maritime Northwest. However, a local nursery owner advised me to use a two-year-old plant, grow in humus rich soil and mulch heavily, and see it survive planted in the ground in Sunset zone 5. I'm skeptical about the survival rate in our climate, but it may be worth experimenting. I grow mine in containers and winter them over in the greenhouse.
The flower gives it away; this genus is in the aroid family—Araceae. The yellow flower looks similar to many in the family, such as our much-maligned Northwest native skunk cabbage, Lysichiton americanus. Unlike our native son, this colocasia flower has the scent of papaya, according to Tony Avent of Plant Delights Nursery in North Carolina. I did not catch a fragrance on my own plant, but then I might have been too nervous to sniff around a skunk-cabbage-like flower. Next time it flowers, I will gingerly inhale its odor, just in case Avent is pulling our collective legs about the reward of a papaya scent, after a deep inhale.
To grow the tallest stems and larger leaves, give them constant moisture, humus rich soil and lightly fertilize once a month. You can grow these bulbs in containers, or plant them in a pot and sink them into a water garden. They add a tropical flair wherever you plant them. They send out runners with a small leaf on the end, which appears to be stems flopping over. Use the runners to propagate more plants by allowing them to coil around the inside of the pot until fully ripe. Divide the suckers out, plant in a one-gallon pot, and overwinter in a sunny, frost-free space. Slowly acclimate outdoors after last frost.
The sap may cause irritation on the skin, so handle carefully.
Photographed in author's garden.