(88) The Expressway Partnership: Greening Chicago's Highways

in HortScience
Authors: A.M. Shirazi1 and C.P. Dunn2
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  • 1 1The Morton Arboretum, Urban Horticulture Research Lab., Lisle, IL, 60532
  • | 2 2Chicago Botanic Garden, Research, Glencoe, IL, 60022

The Expressway Partnership (a project of the Chicagoland Chamber of Commerce's Gateway Green Committee) is an urban landscape project that promises to change the face of the city's expressways. The Morton Arboretum's Urban Horticulture Research Lab., with the support of ComEd (Excelon Corp.), since 2001 has been selecting, planting, and evaluating various cultivars of trees, shrubs, and ground covers in a search for the most suitable and sustainable plantings for the expressway environment. About 470 trees and shrubs were planted plus more than 10,000 groundcovers. In May 2002 these plants were visually evaluated and ranked from 1–5 with one being in excellent condition and 5 being dead. The control plants planted at Urban Horticulture Research Nursery at the Morton Arboretum had 100% survival. The survival rates for groundcovers were: Euonymusfortunei (Virginia Creeper) and Hemerocallis×daylily (day lily) had 80% to 90% survival rates, respectively. Pachysandra terminalis (Japanese spurge) plants died due to either de-icing salt sensitivity, or poor weed control. Syringa pekinensis (Peking lilac), as well as four Syringa cultivars, `President Grevy', `Summer Charm', `Charles Joly', and `James Mcfarlane', had a 100% survival rate. Survival rates for other plants were: Malus sargentii (Sargent crabapple) 93%; Robinapseudoacacia (black locust) ∼93%; Malus cultivars ∼75%; and Pinusbanksiana (jack pine) 75%. Cornussericea (red-osier dogwood) covered with 3 inches of mulch had a significantly better survival rate (90% to 100%) than the mulch treatment (60% to 80%). The growth and performance of other trees and shrubs will be also reported. This research will ensure sustainable and esthetic urban expressway plantings, while enhancing Chicago's stature as a significant urban landmark.