What it means
Creosote is the background of the desert: an open, olive-green shrub, usually head high or less, with tiny paired leaves that look varnished, yellow flowers in spring, and little fuzzy seed balls after. It grows on the flats in evenly spaced ranks, like an orchard nobody planted, and newcomers rarely give it a second look. Then the first summer storm rolls in, and the whole valley smells of it.
That is the word’s real meaning in local speech. When someone in Scottsdale says the desert smells like rain, they mean wet creosote. The desert plants field guide calls it the most common shrub in the desert and the one you have smelled without knowing it, and the monsoon field manual names that smell as the thing people who move away genuinely miss.
You will hear it as “creosote” from anyone under sixty and as greasewood from ranch families and old-timers.
Where you’ll meet it
The flats and lower slopes of the Preserve, the open desert around Pinnacle Peak and Troon, vacant lots, freeway shoulders and nearly every native-desert yard north of Shea. You will smell it best in July and August, just before a storm.
Where the word came from
Creosote is a comparison. The shrub’s smell reminded Anglo settlers of the coal-tar creosote that treated railroad ties and fence posts, and the name stuck to a plant that has nothing to do with it. Greasewood fits the oily, resinous feel of the leaves, though the reasoning behind it was never written down. In Sonora the plant is hediondilla, from the Spanish hediondo, smelly. As an herbal remedy it is sold as chaparral. Who first used any of these names is not recorded.
The smell is the plant’s defense. Creosote’s leaves are coated in oils and wax that cut water loss, and those resins give off their scent when they get wet, so the air over a creosote flat changes the moment a storm’s humid outflow arrives, often before any rain does. Locals describe it as rain itself.
The local proper noun is Greasewood Flat, the open-air burger-and-beer roadhouse the Cavalliere family ran around an 1880s bunkhouse at Reata Pass from 1975 until it poured its last beer on March 31, 2015. Why the founders chose the name is not documented, but the flats around Pinnacle Peak are creosote country, and the Greasewood Flat guide tells the rest of that story.
What it is not
Not the botanists’ greasewood, Sarcobatus, a shrub of salty, alkaline flats and playa edges across the Great Basin and the interior West. Not related to creosote the wood preservative. And not a weed: it is the native plant that holds the desert floor together.
The fine print
Creosote is the great survivor of the North American deserts, dominating the Mojave, Sonoran and Chihuahuan alike. Its small waxy leaves fold during dry spells and drop in severe drought, and mature plants keep functioning at water stresses that would kill most shrubs. Its roots release compounds that inhibit other seedlings, which helps explain the even spacing of a creosote flat and why farmers and ranchers have long found it hard to clear for good.
Its age is the famous number. A single creosote stem system lives about a century, according to the University of Arizona’s Jeff Schalau, but the plant does not stop there: new stems grow at the edge while the center dies, and over millennia a plant becomes a ring of genetically identical clones. King Clone, in the central Mojave near Lucerne Valley, California, is estimated at 11,700 years old and spans up to 67 feet.
Desert peoples used the plant for nearly everything. Its resin fixed arrow points and mended pottery, and the ethnobotanist Gary Paul Nabhan documented its use against at least fourteen afflictions, from colds to wounds; it does have antimicrobial properties. The modern caution runs the other way: as the supplement chaparral, creosote leaf has drawn FDA warnings, and Health Canada advises avoiding it because of the risk of liver and kidney damage. Smell it; do not drink it. The scent can also trigger allergies in some people.