Now that spring is here, you may be thinking about gardening and planting everything from flowers to vegetables and more.
When thinking about what to plant this year, here’s something you should keep in mind. The plants that thrive best where you live may not be the same as in recent years — after the U.S. Department of Agriculture updated its plant hardiness zone map in November.
Based on the average annual extreme minimum winter temperature, the map shows the standard by which gardeners and growers can determine which perennials are most likely to thrive in a given location, according to the USDA.
In the Chicago area, a number of notable revisions have been made to the latest map and the previous iteration, released in 2012.
On the previous map, much of Cook County, as well as fragments of DuPage, Will and Lake counties, were listed in zone 6a, meaning the average annual extreme minimum temperature was 5 to 10 degrees in below zero.
For a large swath of central and northern Illinois – north of Springfield – the extreme minimum temperature was slightly cooler, between 10 and 15 degrees below zero, placing the region in zone 5b.
However, there was one major obstacle.
The far northwest of the state, made up primarily of Jo Daviess, Stephenson Carroll and Ogle counties, was considered a 5a zone, which represents 15 to 20 degrees below zero.
The most recent map keeps most of Cook County in zone 6a. However, unlike before, it extends widely across 6a to cover significant portions of Lake and DuPage County, as well as the majority of Will County.
Other than that, no notable changes have occurred in the Chicago area, although pockets of communities have been moved to a different area.
A major change, however, has occurred in central Illinois.
According to the 2012 map, most of central Illinois, north of Springfield, was listed in zone 5b. Many of the counties previously included in the zone moved to 6a. As the latest map shows, the majority of communities north of Peoria are in region 5b – with a few major exceptions.
A small portion of the northwest corner of the state is still in 5a, although that specific area has become smaller.
Areas of Illinois and associated temperatures are listed below:
- 5a – 15 to 20 degrees below zero
- 5b – 10 to 15 degrees below zero
- 6a – 5 to 10 degrees below zero
- 6b – 5 degrees below zero to zero degrees
- 7a – Zero degrees to 5 degrees
NBC Chicago
