24 Feb, 2010
What’s That After-Rain Aroma in the Valley?
Posted by: Andrea Aker In: Natural Surroundings|Odd Observations|Valley of the Sun
Excerpt from “Valley 101: A Slightly Skewed Guide to Living in Arizona,” a collection of Clay Thompson’s columns for The Arizona Republic. (Originally published September 3, 2000.)
Q: What exactly causes that fresh/earthy scent when it rains in the Valley? It’s a real distinct scent, not flowery or sweet, but more like a fresh, clean smell.
A: Your question worked its way to the top of the pile at just the right time — Tuesday, when we had that delightful morning rain. As soon as the skies cleared we leapt into the Valley 101 mobile research lab, and set out to find the source of the scent.
You are right. There was a truly remarkable aroma in the air, which we soon traced to a half-eaten Big Mac under the floor mats in the backseat of the Valley 101 mobile research lab. While we would not describe this as “fresh/earthy” it was definitely distinctive.
After a stop at the car wash, we sought advice from the estimable Carolyn O’Malley, executive director of the Desert Botanical Gardens and an honorary member of the Valley 101 faculty.
Said she: “It’s the creosote bush. It’s a native and it’s all over the Valley. It is very pungent.” And it smells wonderful after a rain.
In fact, O’Malley knows of a couple who had a sprinkler system installed specifically to rain upon their creosote bushes on evenings when they entertain so their guests could enjoy the aroma.
Creosote bushes are members of the evergreen family and are named for the tar-like aroma of their resin. An interesting thing about creosote bushes: The crown of the plant splits into lobes, which bend over into the soil and send out their own roots and branches, making them clones of the original.
One group of creosote clones found in the Mojave Desert is believed to be about 11,700 years old, perhaps the oldest living plant life we know of.
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