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September 2010 cover image Oh Deer!

Flora Fact: The Old Man of the Desert

You’ll recognize a familiar smell around the ancient creosote bush.

By Sheryl Smith-Rodgers

Fragrant after rains, evergreen no matter the month, the creosote bush has adapted well to the harsh, hot habitat that forms the Chihuahuan Desert of West Texas. So well, in fact, that more than 30 different insects — such as the creosote bush walkingstick (Diapheromera covilleae) and the creosote bush grasshopper (Bootettix argentatus) — rely on its foliage to survive.

“Many of the insects are monophagous, which means they feed only on this plant,” says Matt Warnock Turner, author of Remarkable Plants of Texas: Uncommon Accounts of Our Common Natives. “For that to happen, that means creosote has been here for millions of years.” Indeed, scientists believe creosote bushes may be among Earth’s oldest living organisms. In the Mojave Desert, radiocarbon tests found one creosote stand to be 11,700 years old. Genetically speaking, that is.

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In the spring and summer, Larrea tridentata produces yellow flowers, then fluffy white fruit. Under such arid conditions, though, seeds rarely germinate. Instead, a creosote shrub grows by producing new stems from the outer edge of its root crown. After thousands of years, the plant ring slowly expands and breaks apart as new clones take root.

“It’s important to remember, though, that no one stem is itself that old,” Turner adds. “They’re just all descended from the same seed or plantlet.”

Factoid: The creosote bush is named for the slight tar-like aroma released by its sticky, dark green leaves, especially after rains.

“You can smell creosote bushes as soon as you cross the Pecos River and especially around Fort Stockton,” Turner says.

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