Illinois Planting Zones

Illinois is a long state of close to 400 miles, and that, coupled with a mid-continental placement results in an extremely varying climate that dictates the Illinois planting zones. The majority of the state has a humid continental climate and sees hot, long, wet summers with colder winters. Extremes are the norm for both regions of the state. The southern half leans more toward a humid subtropical climate while the northern half is designated as a warm-summer humid continental climate. The state averages close to around 50 days of thunderstorm activity each year, putting it just above average for the country as a whole. And average precipitation ranges from around 35 to 48 inches, depending on location. Annual snowfall can be anywhere from just about 14 inches in the south to 38 inches in the Chicago region.

Illinois planting zones fall between 5a and 7a, with the northern part of the state being at the lower end of the range. Before planning a garden, it is important to research planting zones specific to the region you will be growing in. Check out Gilmour’s Interactive Planting Zone Map for the exact zone in any Illinois region. Planting zones dictate both what and when to plant, and as a general rule, planting anything rated for the noted zone or below will lead to a successful gardening season. Zones are determined by first and last frost dates.

Any Illinois planting zone will offer a wide variety of both flowers and vegetables. Hosta, peonies, yarrow, daylily and allium are all good choices for foolproof, easy-to-grow options for a flower garden. Many vegetables are also easy to grow in the area. Fill vegetable gardens with tomatoes, beans, beets, kale, spinach, peas and Brussels sprouts, to name just a few. Plants with pretty foliage like coleus and jack-in-the-pulpit also do very well throughout the state.