MONTREAL -- After an opening day today, Montreal is officially home to the largest rooftop greenhouse in the world.

You could even call it a farm: the size of three football fields put together, the greenhouse on top of an old Sears warehouse in Saint-Laurent can grow enough food to feed over 10,000 families a year.

It’s run by Lufa Farms, which Lauren Rathmell co-founded 10 years ago, when she was 21, with her husband.

The new rooftop greenhouse is their fourth project and the biggest one by far. Lufa grows 25,000 pounds of tomatoes per week, they say, all going into homes of customers across Montreal and Quebec City.

It’s “a ton of food, year round, in a place that has a very long, cold winter,” Rathmell said.

In fact, Lufa says it’s feeding 2 per cent of Montreal’s population.

In its mission to do sustainable urban agriculture, the staff take extra measures to avoid waste. 

“We pick to order,” said Rathmell. “So everyday we know what is going to sell for the next day, and we pick down to the unit.”

They use bees and ladybugs for pollination and pest control and even grow the plants in coconut fibre bags so they can collect and reuse water. 

Lufa wants to expand into other Canadian cities. But one city councillor says she wants the model to catch on more in Montreal, too. 

“We have to think how the City of Montreal, in the future, will assure that people will have access to fresh food,” said Lavigne Lalonde, a councillor for Mercier-Hochelaga. 

“Not only tomato in cans, but really fresh food, close to their house, and we have to think further than today and tomorrow.”