Nick Mathison leans over the glass display cases at Trader's Smoke Shop in Peoria and spreads a pile of flaky green herbs across the counter.

"I smoked some of this one night when I was watching a movie," he says, tucking tufts of his red hair under a black baseball cap. "And this really warm feeling started at the top of my scalp and just slowly moved down my face and head. I was on the edge of my seat watching this movie, but I felt really, really mellow. And all it took was one hit."

The herb on the counter resembles sage mixed with crumbled marijuana, but it's fuzzier and fluffier, filled with tiny brown hairs and minuscule crystals. It smells like dry leaves and black licorice and it's being sold in head shops all over the Valley as an "herbal incense blend" meant to be burned for aromatherapy.

Info JWH-018

But people have been smoking it in joints and pipes to get high.

Most of these grassy-looking incense blends, which come in a variety of brands and scents, contain a relatively new synthetic compound called JWH-018. Few studies have been published on the substance — which is legal (for now, anyway) in the U.S. — but recent DEA research indicates it may have the same effect as cannabis (marijuana). And this has made it very popular in Phoenix.

Local smoke shop owners say these "legal herb" incense products, often packaged in one-gram foil packets and sold for $25 to $45 each, are flying off shelves.

"This stuff has been around for years, but it's been very underground," Tim Martin, owner of West Valley smoke shop Herb N Legend, says. "The trend has just exploded in the last 60 days. People are buying a lot of this stuff."

And they're stealing it, too. Trader's Smoke Shop was robbed twice last year, first in early October and again in mid-November. Mathison, the store's manager, says the thieves were selective — they mainly cleaned out the store's three shelves of herbal incense. Last month, the Kind Connection Tattoo and Smoke Shop in Flagstaff was robbed for $300 worth of Spice Gold, one of the more popular herbal incense blends.

Mathison says he works hard to keep this new "legal herb" incense in stock. "Some people come in and buy several bags at once, and they get mad if you're out of their brand," he says. "It's like they're jonesing for it."

"Fake weed" isn't a new concept — companies like California-based International Oddities have been making imitation cannabis buds from herbs like lettuce, catnip, and damiana for two decades, packaging them in plastic tubes and selling them as legal smoke blends named after real strains of potent marijuana, such as "Hydro," "Inda-Kind," or "Thai Stix."

Although these products look like top-class marijuana buds and are advertised as "euphoric smoking experiences," they won't get smokers high, even if you blaze an ounce in one sitting. That's because none of them contains traces of tetrahydrocannibanol (THC), the psychoactive ingredient in marijuana, or any other known psychoactive ingredient, for that matter.

But the herbal incense blends that have hit the market in the past year are different. For one, they're not marketed as something to smoke. Every package specifically states they're to be used for incense or aromatherapy and are "not for human consumption." But the biggest difference is that these incense blends, with names like Pep-Pourri, Serenity Now, and Puff, contain the synthetic chemical compound JWH-018. Most mock pot blends sold as alternative smokes do not.

And the JWH-018 is what's getting people stoned. Though it's used almost exclusively as an ingredient in herbal incense now, it was first developed in 1995 for research, by organic chemist John W. Huffman at Clemson University in South Carolina. He created a chemical compound to try and find cannabinoid receptors in the brain — the parts that THC in marijuana bond with to produce feelings of euphoria — and research shows he was successful.

Christian Steup, a medical doctor and pharmacist at Frankfurt, Germany-based THC Pharm, which makes medicines from marijuana, told Chemistry World that JWH-018 is "four to five times more potent than tetrahydrocannabinol, more commonly known as THC."

Unlike Salvia divinorum, a psychoactive, organic sage plant used in religious ceremonies by Aztec shamans and now packaged and sold to head shops, JWH-018 is entirely synthetic. The effects are also different: People who smoke Salvia may hallucinate or experience spiritual trances; people who smoke JWH-018 claim it replicates a marijuana high: light-headedness or warm-headedness, a feeling of relaxation, even the munchies.

The United States Drug Enforcement Administration conducted a study on JWH-018 in 2009. The resulting report noted the lack of published research on the substance to date, and described four DEA "behavioral pharmacology studies" in which animals were given JWH-018.

"In mice, it decreases overall activity, produces analgesia, decreases body temperature, and produces catalepsy [rigid muscles]," the report states. "JWH-018's activity in all four tests suggests that it is likely to have THC-like psychoactive effects in humans."

In other words, smoking JWH-018 will probably have the same effect as smoking marijuana. And it's perfectly legal.

Of course, you're not supposed to smoke herbal incense blends that contain JWH-018. Just as many head shop owners insist their bongs and pipes are for "tobacco use only," they try to watch their language when discussing herbal incense.

Asked if he's ever smoked any himself, Herb N Legend owner Tim Martin grins and replies, "I've burned it. It's supposed to be an incense, so I really can't discuss the effects of smoking it."

"It's like if I'm selling spray paint at Home Depot," Nick Mathison explains. "I'm selling it to you as paint — now, if you go outside and huff it, that's beyond my control. Well, I'm selling these products as incense. I can't control what people do with them when they get home."

But the government could. JWH-018 has already been banned in nine countries for its alleged psychoactive effects and health risks, starting with Australia in December 2008 and just last month in Russia and Belarus.

Lawmakers in the U.K. and Canada have classified JWH-018 as a "schedule II" or "class B" drug, which puts it in the same category as cannabis and marijuana derivatives. The chief medical officer of the Russian Federation found that JWH-018 has "psychotropic, narcotic effects, contain poisonous components, and represent potential threat for humans."

The DEA has classified JWH-018 as a "drug and chemical of concern," but it is not currently federally controlled under the Controlled Substances Act and is not illegal in any U.S. state — though lawmakers in Kansas are currently considering a bill that would ban it.

Some proponents of legal herb worry about spreading the word that people can legally get high by smoking "incense" containing JWH-018.

"Right now, it's legal, but the government's going to do what it always does," Martin says. "Once they find out people are getting high off something, they'll ban it. But you know what? Somewhere, somebody's already working on the next big thing."