this was actually one of the very few policies brought in by stephen harper that i supported, and you might want to take note of carney once again copying harper. but, harper was right about this. here in southern ontario, greenhouses provide stability for year-round growing seasons, and there was a brief period where you could buy gorgeous locally grown hydroponic tomatoes, peppers and strawberries here in windsor, for cheap.
then they legalized marijuana.
i bicycled from windsor to leamington once a few years ago. amherstburg is less than an hour on a bicycle, but leamington was a full day ride, both ways. i did get back into town before the sun came down. you can smell the marijuana production coming into town from about 10 km away, and the stench overwhelms the whole town. perhaps the residents have gotten used to it, like those who live by niagara falls are used to the sound of the rushing water.
to my dismay, i slowly started seeing the affordable local hydroponic produce disappear. it's obvious that what happened is that virtually all of the greenhouses switched to marijuana grow-ops instead. a few weeks ago, i was not even able to find tomatoes in my grocery store at all, here in what, until recently, was called the tomato growing capital of the world. i had to go to walmart and buy tomatoes imported from mexico.
if you want the greenhouses to grow food and not drugs, you need to write the policies with this understanding in mind and with the realization that there may simply be little you can actually do to get independent growers to grow food instead of drugs, besides growing it under direct state control.
i think that a crown corporation for greenhouse production of produce, specifically, would be the best way to approach this. the government should mandate certain nutrient proportions in the slurry to ensure the food is legitimately healthy, as well. plants absorb what you give them, and you can pump a plant up with almost anything, if you give it to it at the root.
the other issue is labour. i don't have anything against mexicans, exactly, but i don't like the idea of importing mexican slaves to work in greenhouses. this government has made a lot of ai and should realize that robotic fruit pickers are now a thing that exists in reality.
it would be massively beneficial for canadians for the canadian government to eat the capital costs in purchasing this means of production, and holding it in public hands. if we are to have collective ownership of the means of any production, robot fruit pickers in state owned greenhouses is the best way to start.
otherwise, you should be prepared to deal with (1) the reality that drugs are more profitable than food and (2) issues with importing labour to do the work.