Dressed in white overalls, horticulturists carefully tend to small pot plants lined row after row.
Not long ago, orchids were growing in this greenhouse south of Toronto where cannabis plants are now budding.
Recreational marijuana will be legalized Wednesday, and in this 1.8 hectare facility in the Niagara escarpment best known for wineries, they're rushing to be ready.
On one side of the large sanitized greenhouse, workers are busy filling earthen pots: 12,000 cannabis plants are planted each week. On the other, gardeners prune the mature shrubs and prepare cuttings while listening to music.
"It's good for plant growth," said Up director of operations Kevin Epp. "We're installing a sound system throughout the facility."
In a secure room, others stick excise stamps on packages of one and 3.5 grams of cannabis, respectively, that will eventually be sent to each province for sale in accordance with local retailing rules, marking the end of 95 years of pot prohibition.
For licensed growers, such as Up, legalization represents a new business opportunity. But it requires some patience.
It takes four months to grow and harvest cannabis, notes Epp. "Compared to other horticultural plants, it's pretty quick growing but it still takes a lot of time," he told AFP. It's also a new commercial crop and "so it's a slow learning process," he added.
Opening a safe on the premises, Epp is apologetic that it is half empty. "So, right now the value of pot in this vault is Can$6 million. But of course we have been shipping to all the provinces in the past several weeks, so (what's in there) it's gone down dramatically from where we started say three or four weeks ago," he says.
The greenhouse currently produces 12.5 tonnes of cannabis per year. That will increase to 40 tonnes in 2019 after an expansion of the facility.
Epp started Up four years ago with his chief executive Jay Wilgar, who quit a job in the energy sector to jump into the budding cannabis sector. They spent Can$4 million to acquire the greenhouse, which had been used to grow orchids, and adapted it to grow pot. The company is now valued at Can$420 million on the Toronto stock market.
Using an established growing operation was far easier and less time-consuming than starting from scratch.
Dozens of other greenhouses across Canada have been converted to grow cannabis, including one in Montreal that once was the largest grower in North America of pink tomatoes, and one in a suburb of Vancouver that was the largest greenhouse operator on the continent.
"This greenhouse has been in existence for about 11 years, some of (the staff) have been here since the very beginning," said Epp. "When we purchased this facility they came along with it. Basically everyone who was working here previously has taken on employment with us."
Staff say the job has not changed much. Growing orchids or pot plants, there's not much difference. However, cannabis crops earn a much higher return -- as much as four times more, compared to top vegetable or flower crops.
It is also in higher demand, requiring more staff. Up boosted the number of employees from 20 to 140 in just the past year, and plans more hirings in the new year.
The goal, said Wilgar, is to "create a very strong footprint in Canada, which is the biggest legal market in the world."
"We're also looking at what's going on in Europe, (we're) certainly looking at (what's going on) in South America and Australia, but those markets are still so, so young right now, that we're not spending a lot of time and money and resources developing them yet," he added.
For the former wind turbine executive, "cannabis is much less controversial" than renewable energy. "Quite frankly cannabis in my view is far less destructive than cigarettes or alcohol," he said.