Zone change is big news, but don’t go ripping out the garden

When the  USDA Plant Hardiness Zone Map was updated for the first time in 11 years last week, I shared the news of our new zone — 6a — with Mr. Much More Patient, who certainly wasn’t as interested in the update as every gardener I know.

“Well, rip out all the plants. I guess we have to get all new ones now,” he said, tongue firmly planted in cheek.

Rest assured, fellow gardeners, no such action is necessary.

The Plant Hardiness Zone Map shows the average minimum temperature over the last 30 or so years in areas across the United States and can be used to help gardeners determine what plants will grow in their area.

Much of Ozaukee County remains in zone 5b (average low temperature between -10 and -15 degrees), as the entire county was classified on the previous map that was created in 2012. However, the area right along Lake Michigan is now classified zone 6a (average low temperature of -5 to -10 degrees). Zone 6 north of Port Washington is limited to the area right along the lake, but south of Port, it extends several miles inland.

It’s the first time any part of Wisconsin has been considered zone 6, and the area in the northwest corner of the state that had been primarily zone 3a has shrunk to just a few blips on the map.

For as much hubbub as the new zone map caused — gardeners are clearly bored at this time of year — the practical applications for those who find themselves in a new zone are pretty insignificant. Keep in mind, nothing changed overnight. The new map used data from 1991 to 2020, so the change is a reflection of the conditions we’ve been experiencing for some time.

In fact, the seemingly drastic change in the map — about half the country went up a half zone — is at least partly due to a large increase in the amount of data collected and the geographic information system used to pinpoint places like cities and areas near bodies of water that are warmer than surrounding areas.

We will still experience winters with temperatures below our zones — a good reason not to start buying a lot of expensive plants only hardy down to zone 6.

Perhaps the biggest change for Ozaukee County gardeners is that we’ll start to see zone 6 hardy plants creeping into local garden centers. Tempting as they may be, approach with caution. One bad winter could spell disaster.

On the other hand, a new zone map might be just the confirmation that some gardeners need to get a little braver with their plant choices.

Just don’t go ripping out the whole garden.