Critically Endangered Cabbage on a Stick (Brighamia insignis)

Allison Bronson

Richard Gilder Graduate School, American Museum of Natural History, New York, U.S.A.

Take one look at Brighamia insignis, and you’ll see how it got the nicknames “cabbage on a stick” and “cabbage on a baseball bat.” Its quirky appearance aside, this member of the family Campanulaceae is an emblem of conservation in the face of extreme adversity on the islands of Kauaʻi and Niʻihau.

Photo Credit: Wikimedia commons. By C.T. Johansson.

Photo Credit: Wikimedia commons. By C.T. Johansson.

Brighamia is commonly known as the Hawaiian or Vulcan palm, despite having no relation to the palm family (Arecaceae). The ‘palm’ can grow to be 16 feet tall, but usually stands about three to six feet, and makes its home on rocky cliffs of volcanic soil. The plant is endemic to Hawaii – that is, it grows nowhere else on earth, and co-evolved with its pollinator, a species of endemic Hawaiian hawk moth. The hawk moth’s long proboscis was just the right length to reach into the plant’s long, tube-like flowers. In the last century, this hawk moth went extinct (for unknown reasons) and Brighamia was left with no way to distribute its pollen and produce offspring.

The loss of its pollinator only compounded the challenges faced by Brighamia. Like many native Hawaiian species, introduced taxa took a significant toll on the plant’s populations. While feral pigs and goats ate the plants, invasive plants colonized areas barren from fire and competed with Brighamia for space and resources. Perhaps most devastating were introduced spider mites (Tetranychus cinnabarinus), to which Brighamia is particularly susceptible. 
Despite conservation efforts to mitigate these problems, two hurricanes (1982 and 1992) blew many of the surviving plants off their cliffs. In previous years, five populations of this plant were recorded in the wild, each between 45 and 65 individuals. Sadly, as of last year, workers observing these populations believe there may be only a single plant left on the island of Kauaʻi.

Fortunately for Brighamia, its weird appearance has charmed conservationists and horticulturists alike, and extraordinary steps have been taken to bring this plant back from the brink. Scientists and volunteers even rappel down cliffs in order to hand-pollinate the plants, and to retrieve seeds to grow in greenhouses. The cabbage-on-a-stick is commonly bred as an ornamental plant and has become popular among plant enthusiasts worldwide, but despite its success in ‘captivity,’ the plant will never succeed in the wild without a pollinator. So Brighamia is a particular type of oddity: a unique morphology honed over millions of years of isolated island evolution, toppled by a changing environment, and preserved as a relict curiosity among human collections, hopefully to inspire fierce protection of the environment and preservation of endemic species.

References
Lewis, R. 2016. Down to the last plant: The painstaking work of extinction preventionFusion.

Wong, J. 2016. 2016. All Hail the Vulcan Palm. The Guardian.

University of Hawaii. Brighamia insignisNative Plants Hawaii.

Botanist works to save Hawaii’s rare plants. 2014. VOA News.