More than 250 students attended an unusually open Open House at the Agriculture Building Monday to check out the vegetables and wildflowers that grow on the building’s roof.

The Green Roof Open House is one of the newer additions to the SIU Earth Day celebration.

Earth Day is an annual holiday increase awareness and appreciation of the world and its natural environments. It has spurred successful environmental campaigns on issues from climate change and safer drinking water to saving whales.

According to the Earth Day Network website, the first Earth Day was April 22, 1970, when Gaylord Nelson, a former U.S. Senator from Wisconsin, was inspired by a massive oil spill in 1969 and called for an “environmental teach-in.” More than 20 million people participated that year, and Earth Day is now celebrated every April 22 by more than 500 million people in 175 countries.

As a part of the Earth Day movement, Karen Midden, a professor of plant, soil and agricultural systems, holds a yearly open house for the Agriculture Building’s green roof, which is a roof with several garden plots.

“I do it just to share with the public and help educate people about green roofs,” she said.

In addition to the Green Roof Open House, an introduction to agriculture class from Sparta High School with more than 30 students was invited to campus to see the green roof in person.

Michelle Sullivan, a coordinator in agricultural sciences, said it was important to show these students the different environmental practices that they otherwise wouldn’t see.

Midden said she knew nothing about green roofs before the construction of the one at the Agriculture Building.

“My students would always ask me about them, and I’d tell them I had no idea what they were,” she said. “I went into building this one with a clean slate.”

Midden said she went to Chicago in early 2010 to volunteer at green roofs in the city. There, she met a green roof specialist who came to Carbondale for a week that September and helped design and construct one on top of the Agriculture Building.

Green roofs are for more than plants, she said, and they help maintain the environment. They have specially designed bases that catch excess rain, which reduces runoff. This reduction of runoff, in return,

improves water quality.

The medium used for growing the plants is 20 percent organic matter, which is a mixture of a compost that students create, Midden said. The rest is a lightweight dry-heated clay material that is good for moisture retention, she said ,and it allows more surface area to be used.

The base of the structure also serves as insulation to regulate the temperature of the building and save on energy costs. Midden said it is hard to measure the temperature change because the green roof covers a small portion of the building.

The Agriculture Building’s green roof in particular serves as an outdoor classroom and research station for graduate students, as well as a weather station with equipment to monitor temperature and wind direction.

More than 150 students helped build the roof, and about a dozen students help maintain it. Nicholas Seaton, a junior from Bourbonnais studying forestry, is among the students who help out with the roof.

“I just really enjoy being in the outdoors, especially when it comes to something as hands-on as

this,” he said.

Seaton said he and about 10 other volunteers try to put in three to four hours each week cleaning and weeding the roof.

In addition to roof maintenance, the students help tend a garden stocked with tomatoes, kale greens and other plants.

“My students go out in the world and build these things, so this is a great opportunity for them to learn and experience it

hands-on,” Midden said.