The hot pink and canary-coloured hues glow so bright, astronauts can snap photos of them from space.
Fixed atop the largest concentration of greenhouses in North America, the multi-coloured lights have transformed both the night sky in a pocket of southwestern Ontario and the province’s multi-billion-dollar agriculture sector.
Over the last decade, vegetable and cannabis producers have installed thousands of lights inside greenhouses in Leamington and Kingsville, Ont., to grow plants year-round. But the glow emanating from Canada’s most southern region, sometimes seen from as far away as Michigan, has been the subject of both awe and concern, prompting local communities to adopt bylaws limiting the gleam of the greenhouses after dark.
“The technology came in so quick that being able to react and adapt to some of the perceived nuisances took some time,” says Richard Lee, executive director of the Ontario Greenhouse Vegetable Growers, which represents 170 members — most of which are in Essex County.
The rules have reduced the amount of light that spills into the sky. Still, the vibrant glow can be spotted at times from across the region — and even from the International Space Station, as it was in March.
“It’s a lot of light,” says Starr Livingstone, the light pollution abatement officer for the Royal Astronomical Society of Canada’s Windsor chapter, adding that the glint affects their nearby observatory.
“It’s better than it was because at one point the whole sky was just lit up all night.”
The reason some light is still visible, according to Lee and others involved in the issue, involves everything from exceptions within the rules to the cycle of the moon.
“At the end of the day, I think residents in Windsor and the surrounding area, they have some unsettling concerns and probably curiosity on where this glow’s coming from,” Lee said.
“This is where we need to do a better job. They want to understand that they’re being heard,” he said.
“That glow is a byproduct of ultimately the mitigation strategies we’ve implemented, and the trade-off is fresh local food, economic drivers, jobs for those in Ontario and abroad, and being able to maintain that North American food sovereignty.”
The greenhouse boom — and the fight that followed
As satellite photos published by NASA earlier this year show, the number of greenhouses that have popped up in Kingsville and nearby Leamington since 2015 is significant.
Part of that expansion is attributable to Canada’s legalization of marijuana. But the adoption of the lighting technology to grow all sorts of plants year-round has also helped drive greenhouse expansion, say those involved.
“They’re able to get yields that you can’t get from open field farming,” says John Norton, the chief administrative officer for the Town of Kingsville.
“It makes growing vegetables or cannabis or whatever they’re growing more profitable for them to be able to do it in a condensed area,” he said. “So that and technology allowing them to grow year round has really made a huge difference.”
Lee says that demand for fresh produce — especially during the supply chain disruptions of COVID-19 — played a key role as well.
“We were contacted from every level of government trying to identify what else we could grow in a greenhouse,” Lee said.
There’s an economic case for commercial greenhouses to grow tomatoes, cucumbers, peppers, and strawberries, among others, because they produce enough yield, he says.
“So when you look at that food security piece and being able to provide local food, but also economic drivers in these communities, we identified an opportunity to displace a lot of the imported produce that was coming into Canada during those offseasons,” he said.
But the quick adoption of grow light technology was met with some criticism in the community, particularly due to ecological concerns. The region is home to unique Carolinian ecosystems and is within major migratory paths for birds and monarch butterflies.
As a result, both Kingsville and Leamington passed bylaws in recent years to address the growing light pollution from the greenhouses.
What the bylaws do — and don’t — allow
Leamington approved a light abatement bylaw in December 2020 that ordered growers to install light-blocking curtains on the walls and ceilings of their greenhouses. It also forced growers to either shut off the lights or keep the curtains completely closed between 8 p.m. and 2 a.m.
But the companies and OGVG quickly sought exemptions under Ontario’s law protecting normal farm practices, citing the need to open the curtains to periodically release heat and humidity that can harm the plants if either is too intense.
Leamington then passed the current bylaw, which allows greenhouses to open the curtains by up to 10 per cent at certain points in the night.
“When the curtains are fully closed, it blocks the ventilation of the greenhouse,” says William Lubitz, an engineering professor at the University of Guelph who researches greenhouse technology.
“All those plants that are underneath that are intensively growing, they’re producing moisture. There’s heat from the lights, and that has to be allowed to escape,” he said. “What that means though, is there is still some brightness in the sky that’s going to be seen.”
Officials in Kingsville took a different approach, however. The bylaw there does not allow for any curtain “gapping,” as it’s known.
“We have encouraged the growers to find alternative ways to cool the greenhouse,” Norton said. “They can find other ways to let in fresh air than through the roof with the lights on.”
Are greenhouses complying?
Norton said the town ramped up enforcement in the 2024-25 winter period, issuing nine tickets and one more serious $10,000 charge. But this past winter was better, he said.
“As we’ve gone out and done night sky enforcement, we’ve actually laid no charges,” he said. “So we’re feeling much more positive about where we’re at and the operators seem to now have installed curtains and are using them regularly.”
But Lee, the OGVG executive, said his members are following guidelines that indicate 90 per cent curtain closure is what’s achievable. The lack of recent charges is in part due to the discretion given to bylaw officers, who he says have worked collaboratively with the growers.
“Why would you implement such a high-handed bylaw that focuses on 100 per cent light abatement if you have no intention to enforce it? If anything, I think that aggravates residents,” he said.
The municipality of Leamington declined interview requests. Bylaw officers there laid 88 charges against a dozen greenhouse companies, the municipality said in 2023.
In a recent statement, a spokesperson said the municipality “now receives very few complaints related to greenhouse lighting.”
“When concerns are received, municipal by-law enforcement officers conduct inspections and patrols at various times throughout the day and night,” Kelly Sfetkidis, a Leamington communications manager, said by email.
“These patrols take place both in response to complaints and proactively to help ensure ongoing compliance across the community.”
In response to a freedom of information request, the municipality said that since the 2023 news release, there “has been the occasional complaint and by-law enforcement investigated, but no new charges or orders have been issued to date.”
The moon and the clouds
Lubitz, whose team studied greenhouse light pollution and curtain effectiveness in the Leamington area by using drones at night, said they found that “the amount of light that is being emitted by the greenhouse basically reduces proportionally to the amount of opening.”
“When the curtains are completely closed, the manufacturers say they allow less than 1 per cent of the light to escape and we basically confirmed that,” he said, adding that “practical issues” can create extra gaps that allow more light to exit.
Lubitz said that light — despite being minimized — can still appear bright because of other elements, such as weather. Overcast skies can reflect and amplify the glow, and the brightness of the moon can complicate things.
The adaptability of the human eye plays a role, too.
“You can reduce the light emissions to 10 per cent, to 1 per cent, but that can still be perceived as relatively bright as your eyes adjust,” he said. “It’s much brighter than a dark sky.”
