Chicago's winters are famously bitter and its summers just as famously hot and humid. Throw in a few severe storms, a tornado or seiche and it becomes evident that nothing is ever dull in the Windy City. Growing lawn grass in this town can be a challenge but success is all in the timing, whether your turf grows in a traditional ground level yard or on a penthouse roof.
Chicago has a "continental" climate; hot in the summer and cold in the winter. Weather systems move rapidly over the area on the polar jet stream, and Lake Michigan warms up more slowly than the air around it in spring and cools more slowly in autumn because water is denser than air. The lake acts as a natural air conditioner in summer and moderates winter's early cold snaps. The "urban heat island" created by the large percentage of paved area, can cause precipitation to evaporate before it hits the ground or force storms to dissipate or deflect before hitting the city. These factors mean that most Chicagoans may have a week or two longer to garden than their suburban neighbors. It also means that they may need to water their lawns more often; Chicago rainfall averages over 3 but less than 4 inches each summer month, so most lawns will need some water to satisfy their inch-a-week need. The Illinois State Climatologist Office and Chicago Weather Service keep complete data for reference.
Choice of Turf
Chicago sits in USDA Hardiness Zone 5 in the northern part of the country where cool-season grasses grow best. University of Illinois recommends a bluegrass mix for Northern Illinois including Chicago where sun loving Kentucky Bluegrass is the majority of seed. Since many city lawns are shaded in either morning or afternoon, red or chewings fescues provide shade tolerance. Perennial ryegrass starts fast and provides cover for bluegrass, which may take as long as a month to get established. Chicagoland blends balance varieties for the area's growing conditions. Local garden centers carry these local blends.
"Chicago Home & Garden" magazine surveyed several low-maintenance alternatives to grass; Irish moss, Scotch moss, bugleweed, thymes and sedums are all economical options for busy professionals with small city yards. Roof dwellers may want to consider artificial turf, available in bluegrass and fescue models. Veronica Golden Creeping Speedwell is a proven shade groundcover.
According to Garden Illinois, Chicago weather begins to warm in late March. In April, when the soil warms to 50 degrees, apply crabweed killer or fertilizer combined with pre-emergent herbicides. Overseeding should wait until the ground warms to 60 degrees--usually mid-month. Aerate Chicago lawns in April or May. Use broadleaf weed control in late May; Chicago lawn weeds include dandelion, Canadian thistle, plantain and chickweed. In hot Chicago Augusts, bluegrass and fescues may go dormant. Don't increase watering; enjoy the beach. The lawn will recover when the weather begins to cool after school starts. Apply only slow-release fertilizer in September before growing slows and rake thoroughly to keep red and gray snow molds from getting established.