PHOENIX — As powerful storm clouds begin rolling across our desert landscape, a distinctive feature will inevitably come as we begin the monsoon season.
“It’s one of the most unique smells there is,” said one man hiking a trail in Tucson.
“When it first rains, you should be here in order to experience that, it’s amazing,” said another.
But where does the intoxicating aroma actually come from?
Dr. Gary Paul Nabhan, a desert ecologist is sharing the secrets hidden all around us.
“This plant has something like 35 different volatile oils that produce fragrances,” said Dr. Nabhan.
He’s talking about the most potent chemical factory growing in the desert, called the creosote bush. It's long believed to be the main ingredient in that lush monsoon weather scent.
“That plant is glistening with oils on the leaves,” said Dr. Nabhan. “And when the first rains come here, all of that oil will wash off and just flood the air with these 35 different fragrances.”
A new study by Dr. Nabhan and his colleagues has found along with the fabulous creosote, at least 60 different aromatic plants help deliver that smell of rain to the desert, some through blooming flowers, others through "gum" produced from their stems.
“This is another great one, this is one of the acacia’s, they’re the foundation of the perfume industry in parts of southern France and Italy,” said Dr. Nabhan. “We have about six different varieties growing here.”
Nearly everywhere you look, seemingly innocuous foliage helps stir a visceral response for those taking it in. He says while creosote and soil are key ingredients, the smell we associate with rain is far more complex than that. Scorching summer temperatures can intensify the smells, before the wind and rain come along to send them bursting over the public.
Dr. Nabhan’s research partner Tammi Hartung says some studies even suggest the aroma offers some mental and physical benefits. According to Hartung, dozens of scientific studies have documented real health benefits from simply walking along a wooded path and taking in the aromas of certain plants and living soils, a practice known in Japan as “forest bathing.”
“I think it just makes people feel hopeful, it makes people feel positive, joyful,” said Hartung.
She says depending on where you are and the plants surrounding you, that smell will change. So instead of fretting as the thunder claps overhead when monsoon storms begin, be thankful for the wonders our desert world continues to deliver.
“If we had 'smellivision' instead of television, the Sonoran Desert would be on it every day, it’s one of the eight most fragrant places in the world,” said Dr. Nabhan.