A year after it was installed, the "green roof" on the University of Wisconsin-Superior's Yellowjacket Union is healthy and its sedum plants are giving it a distinctive red and green hue.

A green roof is a thin layer of soil mixture and plants that cover a building's roof instead of conventional roofing materials.  It's environmentally friendly because it reduces rainwater run-off, adds a layer of insulation that reduces heating and cooling costs, and extends the life of the roof.

The Yellowjacket Union has one of the northernmost green roofs of its kind, and university officials said it is doing well since it was installed in August 2009.

The 17,000-square-foot green roof is made up of eight to 10 varieties of low-lying sedum plants. Earlier this summer the roof was dominated by a reddish variety of sedum, which gave some passers-by the mistaken impression that the plants were dying. In recent weeks, green varieties of the plants have become more visible.

The plants take two years to mature. At that point, the Yellowjacket Union's green roof will consist of a thick surface of plants of different heights and producing four colors of blooms throughout the summer. The reddish plants that are most visible on the roof now eventually will form the base color below several taller green varieties.

The green roof's plants were installed by Pioneer Roofing of Johnson Creek, Wis. The plants are under a two-year service contract that includes weeding, fertilization, watering and spot seeding as needed. The company says that, to the best of its knowledge, the Yellowjacket Union roof is the first monolithic extensive green roof on a pitched roof in Wisconsin.