Julie Forand is putting a distinct spin on the idea of "green" graffiti.

The recent OCAD University graduate has founded Sprout Guerrilla, a Toronto company that is selling moss-graffiti kits through a campaign called "I heart my city," which aims to encourage people to create public art pieces out of moss.

Moss absorbs the fine particulate matter of air pollution and can help reduce heat-island effect, in which urban areas are hotter than surrounding rural landscapes. Whatever environmental benefit it may have, it can look incredible. The moss-graffiti kits, which Forand is selling for $24, are simple to use, she says. "Just water," mix it and paint it on, she says. Imagine Chia Pet, except slower to grow (about two weeks). There is enough moss in each kit to paint one square foot.

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The mixture can be painted onto any porous surface. Concrete and brick are ideal, Forand says. Glass, not so much. Unlike spray paint, moss graffiti starts as a wet, goopy mixture that is painted onto a surface where it sticks and eventually grows.

Guerrilla gardeners and street artists in Canada have been experimenting with moss graffiti for several years now. Andrea Bellamy, who runs the gardening blog Heavy Petal, first hosted a moss-graffiti workshop for her guerrilla-gardening group in Vancouver in 2009. She has since worked with it many times, and has made many modifications, such as adding a water-retaining polymer to the mixture to help it stick better to walls.

"It takes upkeep," she says. "You need to mist it on a regular basis. I wouldn't do it here in the summertime." Fall is ideal, she says. Just keep in mind that like any plant, you'll need to mist it when it shows signs of drying out.

Jesse Scott, founder of the Canadian chapter of the Graffiti Research Lab, based in Vancouver, discovered moss graffiti at a workshop last year at the Vancouver Hack Space.

"It's a little hard to get fine detail," he says. "It won't keep a clean edge anyway. It gets fuzzy." And just like a plant, "you have to nurse it," at least for the first couple of weeks as it grows.

But the care can be worth the effect. The fact that it's an organic material growing on a wall, as opposed to traditional aerosol graffiti, can make a striking impression.

Forand hopes that people are drawn to moss graffiti not only for its novelty, but as a way of showing civic pride. And for the fans who are especially drawn to it, she is selling a large-scale moss-graffiti mural custom-painted by an OCAD artist for $3,000.

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Of course, it's easy enough to handle that anyone should be able to create their own work, wherever they choose to make their mark.

"I don't encourage illegal activity, but street art is amazing, and why not get people involved in making a statement and greening the city," Forand says.