There was a time when marijuana merchants and union leaders were all but joining hands in the smoking circle, but stepped-up efforts by labor organizers to infuse themselves deep into cannabis commerce have caused the stewards of sinsemilla to rethink the bond.

The legalization of recreational pot in California has set off a scramble for influence in the industry, which is projected to top $7 billion in sales in the state by 2020. Tensions over what role unions should play are rising in Sacramento, in cannabis shops and at places like City College of San Francisco, which has proposed a first-of-its-kind weed apprenticeship course that would largely be run by a union.

“We need a workforce that has minimum training standards,” said Jeff Ferro, the director of cannabis workers for the union seeking to create the class, the United Food and Commercial Workers, or UFCW. “An apprenticeship program provides people with the opportunity to earn as they learn.”

The UFCW has pursued apprenticeship programs for meat cutters, barbers and cosmetologists, so training bud tenders isn’t a stretch. But the college’s plan to funnel mostly dues-paying members into the program raised the eyebrows of its would-be partner, Oaksterdam University, which wants the training to be for all cannabis entrepreneurs regardless of union status.

“We’re meeting to see if this is something we want to pursue,” said Dale Sky Jones, executive chancellor of the Oakland marijuana trade school, which was founded in 2007. “One thing we are talking about is my interest in providing this to more than just union members.”

Jones said the dustup illuminates a larger question among growers, retailers and distributors: Will unionization ruin the buzz?

“The cannabis industry has traditionally been very sensitive to workers’ rights, and the people who have been working in cannabis tend to be happy,” Jones said. “They are not oppressed workers. So the question is, if the workers don’t need representation against management, then what are they getting for their union dues?”

At stake is not just a class teaching the intricacies of the indica-sativa spectrum but the shape of an industry that grew with the legalization of medical marijuana in 1996 and, starting next year, will see hundreds of recreational-use stores open and line their shelves with competing products.

“I think every employer that is looking at a potential organizing campaign is going to have questions,” said Gina Roccanova, a specialist in labor issues for the Meyers Nave law firm. “You are giving up some control and power when there is an organized workforce.”

The role of unions is under particular scrutiny as the state Bureau of Medical Cannabis Regulation works to consolidate the two linchpin laws regulating medical and recreational marijuana. The prickliest issue for legislators is a provision in the Medical Marijuana Regulation and Safety Act that gives the International Brotherhood of Teamsters first rights to transport and deliver pot products.

The deal, negotiated by the union when the permitting system for medicinal cultivators and dispensaries was established in 2015, would require growers and manufacturers to hire a third party to deliver products to retailers, similar to distribution in the alcohol industry. The contracts would probably go to Teamsters-affiliated haulers.

Because the independent distribution model is not in Proposition 64, the decriminalization measure passed by California voters in November, legislators must decide which law takes precedence. The state Legislative Counsel recently said Prop. 64 should trump provisions in the medical marijuana law, but the Teamsters are not giving up and have gained support from some distribution companies, police chiefs and local governments.

Barry Broad, the Teamsters’ state legislative director, said the industry would be courting corruption by allowing growers and manufacturers to distribute their own products, which is known as vertical integration.

“Right now 80 percent of the marijuana produced in California is sent to other states, which is illegal,” he said. “We want to organize the industry, but we want to organize an industry that is well regulated. If you have vertical integration, you are watching yourself.”

Pot growers and retailers are fighting to stop the Teamsters, who they say are trying to corner the market on distribution. In the alcohol industry, they say, the model has pushed up costs, prevented craft brewers from entering the market, and opened the door to organized crime.

“Mandatory distribution does not represent the interests of small growers,” said Steve DeAngelo, chief executive officer at Oakland’s Harborside, the biggest dispensary in the state. He said the coalition supporting the Teamsters is “an unholy alliance” of special interests clamoring for a cut of profits.

The battle has led to an unusual division among unions. The UFCW, which represents pharmacies and retail workers, recently joined a coalition urging the Legislature and Gov. Jerry Brown to allow growers to distribute products themselves.

“We believe that the voters have spoken when they passed Proposition 64,” said Jim Araby, the executive director of the union’s Western States Council.

The UFCW carries weight in the ganja trade. The union was the first to organize marijuana workers in California and was heavily involved in the failed 2010 campaign for Proposition 19, the state’s first attempt to make recreational pot legal.

Oaksterdam worked closely with the union from the beginning, fighting alongside UFCW representatives when the federal government raided dispensaries. Jones credited the union, which now has more than 1,200 card-carrying dispensary workers in Los Angeles, San Francisco, Sacramento, Oakland and San Jose, with legitimizing the movement in the minds of lawmakers.

“What they did was give us early contact with high-level elected officials and legislators,” Jones said. “We were embraced in Sacramento in a whole new way.”

The UFCW negotiated labor neutrality provisions into both the medical and recreational marijuana laws — meaning any farm, dispensary or shop with 20 or more employees must allow workers to meet with the union and organize if they want.

“You’re only afraid of unionizing your shop if you plan to treat your workers poorly or you’re really small,” said Lynne Lyman, director of the California Drug Policy Alliance, who supports the labor movement but opposes a special deal for the Teamsters. “Unions have helped the cannabis industry over the past decade come out of the shadows. I really see it as a good thing, at least the way the UFCW has approached it. They’ve helped write all the bills and have been a stakeholder for many years.”

The City College apprenticeship program is a new twist in the relationship because the UFCW seeks to not only organize existing businesses but groom a workforce that would be union-oriented from the start.

The details of the class still need to be worked out, but Jeff Hamilton, a City College spokesman, said it would fit well with the school’s workforce development program, which uses city and state grants to set up training programs for a variety of jobs.

“Our college is preparing for and making available workforce opportunities in this newly legitimate mainstream industry,” Hamilton said.

Ferro envisions a system in which the UFCW sets training standards and provides trainees, whose union dues would help pay for the program. Students not in the program would be allowed in for an extra fee, he said.

“If a cannabis retailer wants to be a traditional mainstream business, they need to be able to provide employees with benefits — retirement programs, access to health and welfare and skills training programs,” Ferro said. “There are people in this business who are happy to work with us, and there are people in it who are angry they have to work with us, but the industry is going to have to contend with labor around cannabis in California.

“This is not us versus the industry,” he said. “It’s us partnering with the industry.”

Though she said she has long supported unions, Jones wonders how organized labor’s combativeness will square with growers and shop owners who, she said, already collaborate with their workers and are generally known to be quite mellow.

“I expect to see more workers unionized over time, but for that to happen the unions are going to have to be more responsive to what employees and the industry needs,” Jones said. “‘The Man’ in this industry is management, so you better learn how to play in the sandbox with us.”

Peter Fimrite is a San Francisco Chronicle staff writer. Email: pfimrite@sfchronicle.com Twitter: @pfimrite