The mayor of the largely rural community of South Huron, Ontario, was looking forward to an employment boom when a marijuana producer used its soaring stock value to buy an enormous greenhouse on the edge of the municipality’s largest town.

The purchase three years ago, in Exeter, promised to make his sprawling community a major hub for what seemed like Canada’s next big growth industry: legal pot and the high-paying jobs it would bring.

After sitting idle for two years, the one-million-square-foot greenhouse was sold last year for about one-third of its original purchase price of 26 million Canadian dollars, or $20.75 million.