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Guava, guava, everywhere ...

June 30, 2005

Some people collect stamps or coins. Les Landrum, herbarium curator for ASU’s School of Life Sciences, collects fruit.

Guavas, to be specific.

Or, at least, foods made of – or with – guavas.

His ASU lab looks like a grocery store. There are cans, boxes and jars from all over the world, with colorful labels describing guava in almost every form imaginable, including guava paste (which is eaten with cheese), guava jelly and preserves, and even guava soup, baby food and jawbreakers.

Most of the food containers are empty. Landrum, whose research specialty is the myrtle family – which includes the guava – has collected the guava foods over the last 20 years, and he and his family and guests have slowly eaten their way through them.

The herbarium itself is a rich collection of guava. The holdings include more than 260,000 plant specimens, of which about 6,000 are guavas and their relatives.

Landrum, who also is a senior research scientist in the School of Life Sciences, said he became interested in the myrtle family when he was a volunteer in the Peace Corps in Chile 35 years ago.

“I continued my research in graduate school,” he says. “I wrote a grant proposal for the National Science Foundation (NSF) to do monographic studies of Psidium (the guava species), but the NSF said that guavas were not that important economically. So I started this collection.”

The crowded shelves, with labels in many languages, prove that the NSF came to the wrong conclusion.

“It’s an important economic plant all over the world,” Landrum says.

People have been eating guava for a long time, but no one knows the fruit’s exact origin.

The oldest known presence of guavas is in Caral, a 4,000-year-old archeological site on the Peruvian coast.

Landrum says that guavas most likely originated in South America, but their use has spread worldwide.

“People have used guavas medicinally,” Landrum says. “They are high in vitamin C. In South America, people made a tea with the leaves and bark that was good for diarrhea. That knowledge has been passed around the world, to Africa and Malaysia, for instance.”

New research in Japan has shown that guavas may have properties that inhibit tumors, and researchers in Sudan note that the water extract of guava leaves is used to treat bronchitis, asthma, dysentery and diabetes.

Guavas also have influenced fashion and popular culture, Landrum says. “The Spanish word for guava also has worked its way into slang,” he says. “A shirt that doesn’t tuck in is called guayabera, for example. There also are songs about the guava.”

Writers also have waxed eloquently about the offbeat fruit, whose flavor is not easy to describe, Landrum says.

The South American novelist Gabriel Garcia Marquez talked about the fragrance of guava with writer Plinio Apuleyo Mendoza, and Raymond Sokolov, in an article in Natural History, wrote about the Caribbean/Latin-American passion for guava paste.

In addition to collecting guava foods, Landrum also grows guava trees, at home and on the ASU campus. In a “secret garden” of sorts, he has seven guava trees, representing six species, under cultivation at ASU.

Guavas grow best in warm, humid climates. They don’t like intense heat, and they can’t stand frost, Landrum says.

“San Diego has a wonderful climate for guavas, and they have grown wild in Louisiana,” he says.

The guava is “a little kind of weedy tree, a tree that likes disturbance,” Landrum says. “It likes to grow along roads and in pastures. Animals eat the fruit and spread the seeds around. It probably grew along frequently disturbed river banks at one time.”

But why should anyone care about the guava, aside from its nutritional and medicinal properties?

Tracing the tree’s origins and dispersal “might tell us something about how people migrated around the world,” he says. “There is human interest.”

In addition to eating guavas, Landrum has been writing about them for many years.

“My life’s project is to write a monograph about all the approximately 60 species, including their classification, geography and evolutionary history,” he says. “Knowing these may tell us a lot about the last few million years of biological history in Latin America.”

That probably means some new guava treats at the Landrum dinner table.