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DENVER – North Carolina wants to know if marijuana could one day replace tobacco as a cash crop. Louisiana is wondering how pot holds up in high humidity. And Washington state has questions about water supplies for weed.

Colorado agriculture officials this week briefed officials from about a dozen states – some that have legalized weed, others that joked their states will legalize pot “when hell freezes over” – to go over the basics of marijuana farming and swap stories about regulating a crop that the federal government still considers illegal.

The Colorado Department of Agriculture is also working on the world’s first government-produced manual on how to grow marijuana. There’s no shortage of how-to books catering to pot growers both in and out of the black market, but Colorado’s forthcoming guidebook aims to apply established agronomy practices to the production of marijuana.

Yergert conceded that Colorado agriculture officials ignored marijuana entirely for more than a dozen years, from the time voters in the state approved medical pot in 2000 until recreational pot shops started opening in 2014.

“Nobody in our agency ever grew marijuana, so how are we supposed to develop best practices?” Yergert said.

But marijuana’s commercial popularity, coupled with increasing concern over pesticides and unsafe growing conditions, forced the Agriculture Department to stop considering marijuana a running joke and start seeing it as a commercial crop in need of regulation. Colorado sold about a billion dollars’ worth of marijuana last year, making it a cash crop, the same as many others.

Now the state agriculture department is sharing what it has learned about weed with other agriculture departments.

Speaking at a recent soil-conservation conference in Denver, Yergert briefed agriculture officials from other states about how to inspect marijuana and hemp growers, and just as important, how to regulate a plant that remains illegal under federal law.

“You kinda gotta get your mind around it,” Yergert said.

Yergert even took the agriculture officials on a tour of a large Denver pot-growing warehouse, where a marijuana grower showed them the plant’s entire cycle, starting as clones in one room before getting transplanted to bigger and bigger tubs.

The grower, Tim Cullen, also showed the agriculture officials how the plant is trimmed and its psychoactive buds dried for smoking. Finally, the farm regulators saw how marijuana waste – errant leaves and such – are rendered unusable before being thrown away.

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