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Gardens of the Cross Timbers: The Donkey Ear

Becky Emerson Carlberg
Contributing writer
Donkey Ear Kalanchoe basking in sun

The Donkey Ear (Velvet Ears, Palm Beachbells, Sprout Leaf Plant, Tree of Life, Good Luck Leaf or Giant Kalanchoe), after setting a record-breaking growth spurt in the greenhouse, is now producing flowers. It wants to go home to Madagascar.

With leaves that resemble, you guessed it, donkey ears, the succulent is one of the 125 species worldwide of Kalanchoes in the Crassulaceae/Stonecrop family (Echeverias and Sedums). Donkey Ear (Kalanchoe gastonis-bonnieii) has thick leaves and the ability to store water not only in its ‘ear’ leaves but also stems. The plant produces epicuticular wax, a white powder that covers the leaves, some being 20 inches in length. The wax protects against sunlight and helps the plant conserve water. This plant does night photosynthesis. What? In most plants, photosynthesis occurs during the day. Chloroplasts need sunlight to harness carbon dioxide and water that is broken apart and rearranged for food and oxygen production.

Carbon dioxide and oxygen pass in and out of plants through stomata, small pores on leaves (usually more numerous on the undersides). Fewer pores dot the stems. The plant stomata are open during the day for carbon dioxide absorption and release of oxygen. Good thing for us. At night they take in oxygen while releasing carbon dioxide as respiration.

Kalanchoes and other desert species live in dry arid conditions. These plants have developed ways to decrease stress and cut loss of water. Their protected sunken stomata open at night, allowing carbon dioxide to enter. Then, in the sunlight of the next day, the stored carbon dioxide is converted into sugars (food). About 7% of the plant population use CAM (Crassulacean Acid Metabolism), including cacti, pineapples and orchids. Some species have specialized roots, hairs, and cells that can directly absorb water from the air.

The gastonis-bonnerei is the easy part that describes the Donkey Ear. It honors French Botanist Dr. Gaston Bonnier (1853-1922). The genus name Kalanchoe may come from ancient Indian “Kalanka chaya’ -rust and glossy-referring to the Indian species Kalanchoe laciniata which has reddish stems and bright green deeply lobed leaves. It could have originated in China as ‘Kalan Chauhuy’ –what falls and grows. Exactly.

Donkey Ear flower closeup

The Donkey Ear Kalanchoe produces baby donkey ears, little plantlets at the tip of each leaf. All are clones of the parent plant. Within a relatively short period of time a forest of donkey ears may appear around mama if she’s planted in soil. After flowering and setting seeds, my large monocarp succulent will die. She has put all her energy into babies, flowers and seeds. She’s done. Not to worry since several babies have appeared on leaves.

All parts of the Donkey Ear Kalanchoe contain cardiac glycosides, not so much a danger to us in small amounts, according to the Indiana Poison Center, but a real problem for cats, dogs and livestock if they decide to snack on the plant. Deer and rabbits are smarter and avoid the Kalanchoe.

The drought-tolerant tropical has become invasive in Florida, Puerto Rico, Hawaii, Australia and parts of the Canary Islands. Donkey Ear grows across the U.S. in pots. Here in Oklahoma the plant must overwinter indoors with other sensitive plants. The giant Kalanchoe may reach over 2 feet in height and adds another foot in height when it blooms. Donkey Ear likes sun, warmth, moist soil (no overwatering) and good drainage. Hummingbirds, bees, butterflies and ants are attracted to the tubular flowers. Kalanchoe flowers are of the nodding type. There is no “landing platform” for insects or birds.

Madagascar, fourth largest island in the world, home of the Donkey Ear and 60 other native species of Kalanchoes, is also home to 308 bird species, of which 108 are found nowhere else on our glorious planet. No hummingbirds, but there is the very distantly related sunbird. The small, brightly-colored bird looks like a hummingbird, has a narrow downward pointing bill, flies fast and can hover while feeding on flowers. Madagascar has an exotic orchid (Angraecum sesquipedale), discovered by Charles Darwin, that produces an 11.5-inch long, thin, tight tube. No bird or insect can access the nectar except Morgan’s sphinx moth (Xanthopan morganii). The large hawk moth has a tongue (proboscis) that can extend 12 to 14 inches. That’s some tongue.

The climate of Madagascar vacillates between the hot, rainy season and a cool, dry season. The rainforests in the humid tropical eastern coast receive heavy precipitation. Moisture decreases in the cooler central highlands and tapers away in the arid tropical west. Not quite as bone dry as a desert, but close.

The climate has done little to minimize the impact of humans on this unique island. Madagascar has lost 92% of its original forests. Lumber, cattle, coffee, sapphire and nickel mining are major culprits in island destruction. The islanders (18 ethnic subgroups with southeastern Asian and Eastern African genes) brought with them invasive species now driving many of the native species to extinction.

Eclectic flora and fauna live in Madagascar. No lions, giraffes, zebras, hippos, tigers or sloths, but there are lemurs - 111 species and counting. Wild lemurs live only in Madagascar and some islands off the coast of Africa. The nocturnal primates have opposable thumbs, two tongues (primary and a smaller under-tongue right below) and large eyes. The blue-eyed black lemur is the only primate, other than humans, with blue eyes!

Lemurs keep the forests in existence, from pollination to seed dispersal. Six of the nine species of barrel-trunked Baobab trees only live in Madagascar. The life span of this Hibiscus family member ranges from 2,000 to 5,000 years, or not, depending on the global market. The lemurs are disappearing as the baobab trees, valued for their fruit and bark, and rosewood trees, with aromatic dark red heartwood, are harvested. Ninety percent of the lemur population is threatened with extinction.

Recently, Madagascar has experienced a grassroots movement to save the lemurs. Eco tourist groups are protecting select areas and communities have begun to restore habitats. COVID-19 happened when habitat loss affected bats that infiltrated the Chinese meat and animal market. Karma. What goes around comes around.

Our National Geographic Magazine collection

Could not find a local lemur, but the September 2010 edition of the National Geographic had a sobering article on “The Pierced Heart of Madagascar” and a baby lemur for sale.

On the other hand, the Kalanchoe has achieved world status. It was one of the first plants sent into space on a resupply mission for the Soviet Salyut 1 Space Station in 1971. The future of many Kalanchoes (and my Donkey Ear) is more secure.

We all need to work together to make it all work!

Becky Emerson Carlberg

Becky Emerson Carlberg, graduate of Oklahoma State (Plant Pathology) is a teacher, artist, writer as well as certified Oklahoma Master Gardener and Master Naturalist. Contact her at Becscience@att.net.