In the wild, trees pretty much just happen: A seed drops in the soil randomly, germinates and sprouts; if conditions are suitable, a baby tree grows into a big one. In cities, humans tend to take charge, planting seedlings where they want them -- along streets, in parks -- and nurturing them to adulthood. Toronto's Seed Collective takes the process a step further with something called "wireless interactive reforestation." And at Burlington's Firehouse Gallery this month, you can get in on the act. Just bring your cellphone.

The three-member Seed Collective is one of a diverse group of artists in the current exhibition entitled "Human = Nature" (see review this issue, page 53A). What the artists have in common is a sense of acting as agents for change in their communities -- in this case, specifically environmental activism. Together the installations represent a fascinating, uh, branch of contemporary art that is interdisciplinary, collaborative and message-driven. That said, while each of the works here is thought provoking, most are meant to be passively observed. Not so with The Seed Collective's contribution, called simply "SEED."

Installed on the third-floor landing, "SEED" doesn't look like much -- some kind of projector set-up, a screen on the stairwell wall, and a list of written instructions. Here's where your cellphone comes in. Call the number shown on the screen, and a voice on the other end informs you that punching numbers on the keypad will allow you to "plant" a tree on the projected landscape. Hit 1, as many times as you want, and the tree grows; 2 shrinks it; 3 changes its color; and 4 changes the type of foliage. Through the magic of wireless and computer technology -- voila! -- your tree becomes part of a virtual forest.

So how does this work, exactly, and what's the point? "The number is going to an online phone system," explains Firehouse Curator Ruth Erickson. "The number calls a website managed by a computer in Toronto." While the technology is hard to comprehend, Erickson concedes, what happens next is less so. The point of Seed Collective's work remains to be seen, literally: The phoned-in trees are going to translate to 150 real ones being planted in Burlington next year, thanks to the largesse of Seventh Generation. "They liked the combination of technology and environment, how solutions are going to depend significantly on technology, so they sponsored the project in full, and agreed to donate money to Branch Out Burlington," says Erickson. "The ultimate goal of The Seed Collective is to connect the project with businesses and nonprofits that work on reforestation issues."

A paean to the social, communal, environmental and economic benefits of trees can be found at www.seedcollective.ca. "Human = Nature" is at the Firehouse through July 30. Go ahead, plant one.

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If your proclivity for interactive art is more about pent-up rage, this month's "iron pour" might be just the thing. At least the part about smashing up old radiators. Metal fabricator John Marius, one of nearly a dozen artisans at Burlington's Pine Street Studios, has organized a weeklong workshop for anyone interested in learning the art of casting iron. It begins July 22 and takes place at the 339 Pine Street shop. So far about 11 have signed up; Marius says he can take nine more. "I'm inviting people to come make their own molds," he adds. "I don't know that much about it myself, and I want to learn."

The cost is fairly lightweight: a mere $67 for the class, and $3 per pound for the iron. The heavy part comes from those radiators, procured from Queen City Iron & Metal. The idea is to pound the iron to smithereens -- 2- to 3-inch pieces, to be precise -- and melt them down in a "cupola furnace." This 4-foot-high tub is tough enough to heat heavy metal to 2800 degrees Fahrenheit. A pole running through its top allows the cupola to be tipped, pouring molten iron into artist-made molds. "You have to wear sunglasses to look at it," Marius cautions.

The tipping point, as it were, will be demonstrated by "the spectacular Elijah Sproles, all the way from New Orleans," as Marius describes him. The master iron man, whom Marius met at a sculpture park in Minnesota, has been trying to dry out and salvage his foundry flooded by Hurricane Katrina. Talk about rage. "We're paying for his gas money, but he's not charging us anything," reveals Marius, who invited Sproles to spend some time in "beautiful Vermont."

Marius generally makes functional art from metal -- one of his chairs is displayed at Pine Street Art Works. He just returned from Bonnaroo, a music festival in Tennessee, where he was the sole metalworker on the production crew. His latest creation? "I made a 24-foot-diameter chandelier that hung in one of the stage tents," Marius explains. Unfortunately, Bonnaroo gets to keep it.