“We have a drug problem in America. And I’m telling you if we don’t solve this, we’re in trouble,” Jack Christie told the chamber at a City Council meeting this summer, shortly after 16 people overdosed on the drug called kush in Hermann Park. “So don’t listen to California, going from hemp, to medical marijuana, to recreational,” the councilman advised. “That’s the way they insidiously get into society and hook the society for profits, and the side effects can be as great as death.”

There was only one problem with Christie’s rousing speech: Kush is not—repeat, is not—marijuana. You can hardly blame him for not knowing that, though. Synthetic marijuana is smoked in the same fashion, and its compounds interact with the same part of the brain as the active ingredient in natural marijuana, THC. Adding to the confusion, which seems to be by design, certain strains of natural cannabis also go by the name “kush.”

Hence this quick kush primer:

What the heck is kush?

Sometimes called spice or K2, it’s a mix of “plant matter” sprayed with an ever-changing host of chemicals, in sometimes dangerously high proportions. The original formula was invented by a chemist who had no idea that his medical-research papers, funded by the National Institute on Drug Abuse, would be used to mass-market dangerous drugs around the world.

How easy is it to get?

The Texas Legislature tried to ban the chemicals used in kush in 2011, but scientists just tweaked their formulas so that the new stuff, slapped with a “not for human consumption” label, was technically legal. Houston passed a ban on synthetic marijuana in 2014, so no version of the drug is legal here anymore; today it carries a fine of $2,000 per package. Nevertheless, kush is still on offer in some local head shops, not to mention just a click away on the internet, where it’s available in huge quantities for cheap.

What is the city doing about it?

After the recent slate of Hermann Park overdoses, Mayor Sylvester Turner announced an initiative to increase police and park rangers’ presence in the four areas around town where use of kush is most prevalent—Hermann Park, Tranquility Park, Main Street Square, and Peggy’s Point, the little park on the corner of Main Street and Richmond Avenue.

How dangerous is it?

Side effects include paranoia and hallucinations, which can result in violent behavior and death. Since September 2015, nearly half of the 3,000 overdose calls fielded by city paramedics were for kush, according to Mayor Turner, clogging our emergency rooms and lengthening wait times for ambulances.

In the same period, how many regular-old-marijuana-related calls did the city receive?

126—less than 10 percent of the number for kush.