Sunday, March 4, 2018

Plant Story--Coral Trees, the Erythrina species

Erythrina, coral tree

Pretty red flowers on a small tree, the flowers upturned or curved like crescents. Called coral trees or coral bean, the genus is Erythrina in the pea family, Fabaceae, and they are found all around the tropical world.

My most recent encounter with a coral tree was with Erythrina crista-galli, the cockspur coral tree (crista-galli is Latin for cock's comb) in Argentina, where, called ceibo, it is the national flower. Cockspur coral tree is native to northern Argentina and nearby areas in Paraguay, Uruguay and southern Brazil. It is the national flower of Uruguay, as well.

Which tells you how spectacular the cockspur coral tree is in flower.

cock spur coral tree, Erythrina crista-galli
In its native region, cockspur coral tree grows in moist areas of subtropical forest.  With dramatic red flowers, of course it became part of the local folklore. For example the Guaraní of the Paraná River region told the story of Anahí, a young woman who lived near the Iguazu Falls. She was small and not very pretty but she had a beautiful voice and sang to the animals and plants in the forest. One day her people were attacked--in some versions by another tribe, in other versions by Spanish conquistators--and there was a fierce battle. Anahí was captured but in the night killed the guard and escaped. She was recaptured, and in retribution, tied to a tree and burned alive. Burning, she sang, asking divine protection for her people and their homeland. In the morning, instead of ashes, where she burned bloomed a beautiful ceibo tree, red like flames, a symbol of strength and courage. 

Cockspur coral tree flowers in the subtropical summer, which is October to April in the Southern Hemisphere. In Argentina it is celebrated on the Day of the National Flower, November 22.

Another species of coral tree, coastal coral tree or South African coral tree, Erythrina caffra, is the official tree of the city of Los Angeles, California. As the name indicates, it is from southern Africa. See photos link

There are approximately 130 species of Erythrina with at least one species native to all the regions around the tropics. I have a collection of plant books and I found different species in Baja California,  Costa Rica, Argentina, the southeastern United States, Africa, India, China, Australia and Hawaii. For example see plants from South Africa (link), India link, and Australia (link).

The name Erythrina comes from a Greek word for red, erythros, the same stem as the word for red blood cells, erythrocytes. Its worldwide distribution means there are dozens of common names in dozens of languagues.

Flowers of the various species range from red through orange, although a few species' flowers are white. Most are pollinated by nectar-feeding birds which reach into the long tubes for nectar. Hummingbirds hover, so the flowers of trees from Costa Rica--immediately above--could be easily visited by them. Only the New World has hovering birds, however, so Erythrina species from Asia and Africa generally are arranged to allow birds to perch when taking nectar. See for example Los Angeles' Erythrina caffra link. And out of 130, there are doubtless some other pollination systems.

Erythrina crus-galli, Buenos Aires, Argentina
Cockspur coral tree in a park in Buenos Aires, Argentina
They can get pretty large, though nothing like the size of a large oak or a banyan
Most coral tree species are spiny, some very spiny. Most are small trees although a few are so small you would call them shrubs. The wood is light and porous, good for rafts, surfboards, model airplanes and even bottle stoppers and corks but not very good for construction. However, the branches root easily so that in tropical countries that prefer living fences such as Costa Rica, frequently they are used for fence posts, which then send down roots and grow.

living fence, Costa Rica
Living fence, but not coral tree--imagine the fence with brilliant red flowers!
The fruit is a pod like a bean pod (it is in the same plant family as beans, after all) and the seeds are often bright red, easily strung as beads. (See photos link). The plants are quite toxic, especially the seeds, and have a variety of uses in folk medicines, as sedatives, to reduce fever, as anti-depressants, as an astringent and more. 

Hawaii has an endemic coral tree, Erythrina sandwichensis. The Hawaiian name is wiliwili. Wili means twisted, referring to the way the seed pods twist open. The specific epithet in the scientific name, sandwichensis, means "of Hawaii." When Captain Cook, sailing for England, discovered Hawaii in 1787, he named the islands for the Earl of Sandwich, who was First Lord of the Admiralty at the time. Hawai'i is the name the natives gave their islands, and we switched to calling them the Hawaiian Islands sometime in the 1800s.

Wiliwili is believed to be endemic to Hawaii, not brought by Polynesians, let alone by Europeans, so you have to imagine a little bean, or a bean pod, surviving the 2,300 miles of ocean to reach Hawaii. (About wiliwili: link).

wiliwili, Erythrina sandwichensis
This is a big old wiliwili tree flowering on the big island of Hawaii,
the flowers salmon colored rather than red
Because the coral trees are so handsome, they have been planted all over the world, and between their beauty, rather nice wood and medical value, they are woven into cultures from the Americas to Africa to India. The beak-like reddish flowers and bean pod makes them relatively easy to recognize, despite their diversity.

Comments and corrections welcome.

Blogpatagonia link
Duke, J.A. and R. Vasquez. 1994. Amazonian Ethnobotanical Dictionary. CRC Press, Boca Raton, Florida.
Herrera-Sobek, M. 2012. Celebrating Latino Folklore. An Encyclopedia of Cultural Traditions. ABC-CLIO publisher. 
the flower link
Zuchowski, W. 2007. Tropical plants of Costa Rica. Cornell University Press, Ithaca, New York.
and the links within the post

Kathy Keeler, A Wandering Botanist

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