Chicago's rooftops are sprouting green with flowers, plants, shrubs and grasses.

If you want to understand the potential of living roofs, pop by the public rooftop gardens at Chicago Botanic Center's Rice Plant Conservation Science Center.

"Almost anytime you go up there, you're going to see something cool," said Richard Hawke, a plant evaluation manager at the center who has watched the garden grow and thrive.

Chicago Botanic Garden green roof
Credit: Courtesy of Chicago Botanic Garden

Hawke credits former Mayor Richard M. Daley for kick-starting the area's green-roof movement in 2001 with a groundbreaking project that covered 20,300 square feet of Chicago City Hall with more than 150 varieties of plants. The green roof saves the city about $5,000 on utility bills and can keep the roof temperature up to 80 degrees cooler than nearby buildings with black roofs.

Chicago now claims more than 350 buildings and businesses with sky-high prairies, gardens and vegetable plots averaging 5,234 square feet each and collectively covering close to 5.5 million square feet, according to city statistics.

While many are private and set up for economic and environmental incentives, Hawke sees green roofs evolving to be more social and interactive as businesses use the gardens as gathering spaces and to enjoy nature or to use the area for harvests.

Here's a look at some of Chicago's most inspirational green roofs:

1. Rice Plant Conservation Science Center

Chicago Botanic Garden green roof-South
Roof Garden South
| Credit: Courtesy of Chicago Botanic Garden

Doubling as a living laboratory, this Chicago Botanic Garden complex in Glencoe includes 16,000 square feet of rooftop gardens with soil depth of four to eight inches. Roof Garden South, which features a natural prairie-like setting with native plants, bursts with color in early June with orange butterfly weed, lavender, white pestemon and pink roses.

Chicago Botanic Garden green roof-North
Roof Garden North
| Credit: Courtesy of Chicago Botanic Center

Green Roof Garden North feels like a more traditional, organized flower garden that fills with bulbs and moss phlox flowers in early spring and waves of other flowers throughout the season.

2. Millennium Park

Lurie Garden in Millennium Park
Lurie Garden in Millennium Park
| Credit: John Noltner

This internationally popular and interactive park, which opened in 2004, ranks among the largest green roofs in the world at 24.5 acres. Visitors to park highlights such as the J. Pritzker Pavilion, Lurie Garden and Cloud Gate sculpture may not realize the park is a green roof because it's at ground level, but it was constructed over parking garages and a rail yard.

3. Soldier Field

The home of the Chicago Bears transformed the roof of a four-story parking garage into a 5.5-acre rooftop park, part of a total of 17 acres of reclaimed public waterfront parkland. Former parking lots now showcase an area for outdoor museum exhibits, a sledding hill, a winter garden, a terraced park and more.

4. McCormick Place

A half-acre garden on top of North America's largest convention center produces 8,000 pounds of herbs and vegetables (beets, peppers, lettuce, carrots and more) each year for use in the center's restaurants. As a bonus, 20,000 honeybees produce 50 pounds of honey a year. The rooftop is open occasionally to the public for special events.

Your Own Living Roof

Anyone inspired to consider a smaller-scale green roof can tap Chicago's Midwestern expertise—especially in choosing plants that can handle extreme seasonal temperatures and higher winds found on rooftops. Other considerations include: finding out if a roof can handle additional weight, pursuing any permits or licenses for the project, and finding specialists in roof access and safety, irrigation, planting materials and the ideal depth.

The city of Chicago put together this starter guide.

The website also provides resources, supplies and contractors that can be searched by city and state.