Rooftop Bog

Few Midwestern landscapes are as strange as a tamarack bog.  Here in the heartland we’re better known for endless acres of corn and soybeans, picturesque forest-fringed lakes, and rolling hills carpeted with oak or maple forests. In certain places, though, mostly in the northern reaches ofn Minnesota, the land is sopping wet. Hundreds of thousands of acres are covered with a spongy surface of sphagnum moss, sedges, and other plants that love their feet moist and their soils bereft of nutrients. Walking in such a bog is like traipsing across miles of down comforter.

And growing from that mossy mattress are tamarack trees. These conifers, sometimes called larch, have the rare distinction among needle-bearers of dropping their leaves in the winter. In fall, they turn a brilliant golden, then sleep through the cold months like those oaks and maples farther south.  “What I love about these tamarack bogs,” the artist Christine Baeumler told me recently, “is that they’re exotic, but in our own midst.” I was talking with Baeumler under the Mies van der Rohevian black steel main entrance canopy of the Minneapolis College of Art and Design (MCAD). A tamarack bog grew directly above us.

Baeumler’s project, “Reconstructing the Landscape: A Tamarack Rooftop Restoration,” is a collaboration with local firm Barr Engineering and was funded through a McKnight Foundation fellowship. The 16-foot by 24-foot foot canopy is home to about 32 species of native bog plants, a pool of open water, and a grove of small tamarack trees. The idea behind the project is to bring visibility to this odd and relatively unknown ecosystem.

But it’s also a functioning green roof. The old membrane and ballast gravel were removed and a new membrane installed. Two scuppers through the existing 4-inch high parapet were blocked (one only partially, to ensure two inches of standing water on the roof). A company called Boreal Natives salvaged bog plants, soil and all, from a utility corridor up north, grew them out in 1-foot by 2-foot trays in a greenhouse for a few months, then plopped the whole spongy cross section onto the roof. Excess water overflows one of the scuppers into a custom-fabricated metal cistern, and is returned to the roof by a solar-powered pumping system.

“I don’t think that I’ve seen a bog [functioning] as a green roof—ever,” says Kurt Leuthold, the Barr engineer who collaborated with Baeumler. It does seem to be working. The tamaracks have grown about six inches since they were installed last May, and the Labrador tea, sedges, cottongrass, sphagnum moss, and other species are green and lush.

The best views of the bog are from the second story of MCAD’s gallery space, and from an adjacent skyway that passes alongside and slightly above the canopy roof. “Reconstructing the Landscape” is scheduled to be in place through November 2013, though Baeumler hopes MCAD will decide to keep it permanently. In any case, visitors should expect a lovely fall show, as the golden tamaracks illustrate a slice of bog-country in the heart of Minneapolis.

Photo Credit: Rik Sferra all copyright reserved, as noted; Adam Regn Arvidson, all others

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