Chicago City Hall, Chicago, IL
Completion Date: Spring 2002
Former Network Contractor
Where am I? It didn’t look or feel like I was in the heart of downtown Chicago when I stepped out onto the Chicago City Hall green roof this morning, but there I was. This roof is full of native and appropriate non-native species including grasses, perennials, and vines. The combined effect evokes the feeling of walking through a wildflower meadow.
The green roof profile consists of a Roofmeadow Type II with 3.00 inches of media and Type III with 9.00 inches of media. In order to appropriately maintain the garden, the city employs gardeners whose sole responsibility is to care for the green roof. Each year new species of plants are added to this garden on an experimental basis such as the native Shooting Star plant. (Dodecatheon meadia)
The Dodecatheon is doing very well on this roof!
This green roof is by no means a “low maintenance” project. In fact, it’s just the opposite. This is a high maintenance garden and, as any experienced gardener knows, maintenance requirements should always be considered when designing a garden. Case in point, the roof is predominately planted with herbaceous perennials and grasses, so all of the plant material is cut back each year in late winter and removed from site to allow fresh new growth to emerge in the spring.
In an inner city with searing summer heat, irrigation is required to sustain an intensive planting such as the one on Chicago City Hall. Some might assume that since native species were incorporated into the planting plan irrigation would not be needed but that’s not so on this green roof. Remember we’re dealing with 3.00 to 9.00 inches of green roof media and most of the larger native species of grasses have deep root systems and need more soil depth than that to survive.
Vines such as our native Bittersweet (Celastrus scandens) are used to screen utilities from view. Vines require quite a bit of maintenance, especially during the establishment stage. The Celastrus is a twining vine and often requires gentle persuading to climb a trellis and not onto adjacent plants.
One of the observable benefits of a green is the insect life attracted to the roof by the plants. Dragonflies on the Wild Blue Indigo (Batisia australis) as well as ants and millipedes were all in view today. The city of Chicago keeps bees on this green roof and the hives are thriving due to the diversity of plants and the range of bloom times on the roof. I’m told that the honey collected from the hives is pretty great.
Please see Roofmeadow’s Chicago City Hall green roof case study for more technical information and watch my video to see what it’s like high up on a roofmeadow.