what planting zone is illinois
Hardiness refers to a plant's ability to tolerate temperature. The USDA Plant Hardiness Zone map divides the United States into zones according to the average minimum cold temperature. A hibiscus brought to Illinois from Southern Florida will not survive outdoors all year due to its hardiness. Most of Illinois is classified zone 5. Plant material listed for this zone is able to survive the average minimum temperature between -10Â° and -20Â°F. Zone 5 has been further divided into 5a and 5b. Zone 5a average minimum temperature is -15 to -20Â°F, and zone 5b average minimum temperature is -10 to -15Â°F.