Right now, CBD is all the rage, but ten years ago it took a team effort of growers, researchers, breeders, and scientists to identify the few remaining high-CBD strains in existence and match them up with growers willing to take a chance on the then obscure cannabinoid. Next, they had to convince profit-minded dispensary buyers to stock their shelves with strains that don’t get you high.

Not surprisingly, those efforts were met with much initial skepticism. But then it quickly became apparent that CBD-rich strains appeal to a lot of people, particularly those seeking the medicinal benefits of cannabis without any intoxicating effects—including seriously ill children.

The Point of It All

The earliest pioneers of cannabis horticulture (circa 10,000 years ago), though new to agriculture itself, would certainly have been capable of using selective breeding to enhance desired traits from generation to generation. If nothing else, then by simply culling out plants that grew poorly over the course of the season and planting seeds from crops that flourished.

So what are desired traits when it comes to cultivating cannabis?

Growers would want plants that thrive in their local climate, including resistance to mold, disease, insects, and drought. But that’s just to ensure a reliable supply.

In a time long before modern science, the most observable and accurate way to gauge potency was by ingesting some of your harvest and seeing how high you got.

The point of it all is potency, and in a time long before modern science, the most observable and accurate way to gauge potency was by ingesting some of your harvest and seeing how high you got. Which is all pretty much any cannabis breeder had to go on until about ten years ago, when analytic testing labs became widely available in California and other states with legal medical cannabis.

Turns out the medicinal and psychoactive effects of a particular cannabis strain depends on a complex interplay of cannabinoids, terpenes, and flavonoids that researcher Ethan Russo has dubbed the entourage effect. In 2006, Russo led a team that published a fascinating paper titled Phytochemical and genetic analyses of ancient cannabis from Central Asia, which has an abstract that opens like something out of Indiana Jones.

“The Yanghai Tombs near Turpan, Xinjiang-Uighur Autonomous Region, China have recently been excavated to reveal the 2700-year-old grave of a Caucasoid shaman whose accoutrements included a large cache of cannabis, superbly preserved by climatic and burial conditions.”

The samples were so “superbly preserved,” in fact, that Russo and his team were able to have them lab tested, and found through gas chromatography that the 2,700-year-old shaman stash appeared to be “a high-THC cannabis strain wherein CBD is only a minor component.”

The Unknown Cannabinoid

It wasn’t that ancient cannabis smokers had it out for CBD, they just didn’t know such a thing existed. The compound wasn’t isolated in a lab until 1940 and remained obscure long after that, largely because it doesn’t get you noticeably high.

Since the 1980s, studies have hinted at CBD’s potential for treating pain, insomnia, nausea, anxiety, spasticity, MS, Alzheimer’s, cancer, seizure disorders and a host of other serious conditions. But for the general public, it was completely unknown—and since CBD actually works to temper the high of THC, cannabis breeders had been unwittingly breeding it out of the cannabis gene pool for 10,000 years.

When Steep Hill Lab in Oakland opened in 2007, the first commercial medical cannabis testing lab in the United States found that the cannabis flowers they tested averaged over 15% THC, but only one in every 600 samples reached 4% CBD.

The Search for CBD

In 2010, journalist Fred Gardner (editor of O’Shaughnessy’s: The Journal of Cannabis in Clinical Practice) and author Martin Lee (Smoke Signals, Acid Dreams) co-founded Project CBD, a non-profit educational clearinghouse for physicians, scientists, growers, cannabis-testing laboratories, patients, and retailers interested in learning more about the medical utility of CBD.

They fully understood that CBD has important benefits, but that finding CBD-rich cannabis in the underground market was virtually impossible.

Through years of careful research and reporting, they fully understood that CBD has important therapeutic benefits, but that finding CBD-rich cannabis in the underground market was virtually impossible. So they teamed with Steep Hill Labs and Harborside Health Center (then the nation’s largest medical cannabis retailer) to begin immediately flagging any sample that tested high in CBD. Project CBD would then meet with the grower, and work to ensure that their particular strain proliferated and reached patients who could benefit.

Most of these growers understood their heirloom strains had unique properties, but didn’t know why—including Lawrence Ringo, the late proprietor of the Southern Humboldt Seed Collective. Ringo began growing cannabis while still a teenager, and 40 years later became the first California plant breeder to stabilize a CBD-rich strain with his much-beloved Sour Tsunami.

In 2015, Dr. Sanjay Gupta—CNN’s Chief Medical Officer—reported on the Stanley Brothers in Colorado, who were having tremendous success treating pediatric seizure disorders with their high-CBD strain Charlotte’s Web, named for their most famous patient.

“Take the case of [six-year-old] Charlotte Figi, who I met in Colorado,” Gupta said by way of introducing his mea culpa on medical cannabis. “She started having seizures soon after birth. By age 3, she was having 300 a week, despite being on seven different medications. Medical marijuana has calmed her brain, limiting her seizures to 2 or 3 per month.”

This after the poor girl endured five years of failed pharmaceutical cocktails, and a series of terribly painful procedures that left her unable to walk, talk, or eat.

So no wonder, once they saw that incredible story on CNN, other families facing similar circumstances began to agitate for access to CBD. Along the way, the rest of the world got let in on the secret that there’s a lot more to weed than just THC. CBD is officially “trendy” now, but nearly a decade after the founding of Project CBD, there’s still a relative dearth of CBD-rich strains.

Though that’s changing—quickly.

The Hempire Strikes Back

Scientifically, the plant you smoke to get high and the plant you use to make rope are the same species. But legally, hemp is defined as a Cannabis sativa plant that’s less than 0.3% THC on a dry weight basis—no matter how much CBD (or other cannabinoids) it produces.

But wait, does that mean anyone who registers with their state can legally grow a crop of hemp that’s 15% CBD and looks just like any other budding resinous sinsemilla cannabis plant? Sure does. And if you don’t believe me, here’s the federal government’s new definition of hemp, from the 2018 Farm Bill, with my emphasis added:

(1) HEMP.—The term ‘hemp’ means the plant Cannabis sativa L. and any part of that plant, including the seeds thereof and all derivatives, extracts, cannabinoids, isomers, acids, salts, and salts of isomers, whether growing or not, with a delta-9 tetrahydrocannabinol concentration of not more than 0.3 percent on a dry weight basis.

Andrew Gruver is the head of operations at Tweedle Farms in Oregon, a retailer of high-CBD hemp flower that currently ships 15 different varietals to (almost) all 50 states.

“There are certain hemp strains that for me are pretty indistinguishable from high quality outdoor cannabis other than the lack of THC.” Andrew Gruver, Head of Operations at Tweedle

“There are certain hemp strains,” he tells Leafly, “that for me are pretty indistinguishable from high quality outdoor cannabis other than the lack of THC.”

His favorite at the moment is Sour Space Candy, a descendent of Lawrence Ringo’s original Sour Tsunami with a cannabinoid content of 16.52% CBDA and .08% THC.

“It’s loud, it’s resinous, and it tastes good,” Gruver says. “Also, it’s high in terpinolene, which a lot hemp strains are not. Hemp typically exhibits high levels of myrcene, caryophyllene, or maybe some pinene. But we also get really interesting terpenes like bisabolol, farnesene, valencene.”

His other favorite strains include Hawaiian Haze from Oregon CBD, Berry Blossom from HGH, and Kush Hemp from Sovereign Fields. And we’re just getting started.

The search for high-THC cannabis dates back millennia, but this current exploration of CBD-rich cannabis breeding remains in its infancy.

David Bienenstock Veteran cannabis journalist David Bienenstock is the author of "How to Smoke Pot (Properly): A Highbrow Guide to Getting High" (2016 - Penguin/Random House), and the co-host and co-creator of the podcast "Great Moments in Weed History with Abdullah and Bean." Follow him on Twitter @pot_handbook. View David Bienenstock's articles