Marigolds in October The Editorial Board

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Marigolds, zinnias, and alyssum were still flowering in October in my yard because of this fall's unusual warmth. Will it become the new normal?

Last month the USDA released an updated plant hardiness zone map. For many Minnesotans (but not all), our zones have warmed up into a new half zone.

The plant hardiness zone helps growers choose plants that are more likely to survive the weather in an area. For example, tropical bananas won't survive Minnesota winters, but we have some mighty fine apples.

A gardener can look up their plant zone by zip code at the website https://planthardiness.ars.usda.gov/

My trusted gardening resource is the University of Minnesota Extension. In the article “A new plant hardiness zone map from the USDA,” Julie Weisenhorn, Extension horticulture educator, explains some of the finer points of the map and how it applies to gardening. She explains that choosing plants based solely on the guide doesn't guarantee success because gardeners need to consider other factors, such as “soil type, light, space, wind and overall care.” I agree. From my past mistakes, I know that I can't place a plant that says “good drainage required” in clay soil even if the zone is correct.

Weisenhorn gives details, such as that the data to create the new map is from the years 1991-2020 and uses over 13,000 weather stations. Thirty years of averages show the extremes, which is (no surprise) cold in Minnesota.

With new technology, the map has smaller zones to account for topographical details, such as warmer spots in cities with heat-holding concrete, higher elevations, and winds off of water that doesn't freeze in winter.

I have moved from zone 4a to 4b. This doesn't surprise me too much because I've been experimenting with zone 5 perennials in my garden the past couple of years. I keep them protected from the wind, and they grow well.

Other gardeners have similar stories. In an NPR

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story, “'It feels like I'm not crazy.' Gardeners aren't surprised as USDA updates key map” by Julia Simon, Megan London in Hot Springs, Arkansas, is thinking about growing mandarin oranges with her new zone 8a. She also expressed concern about climate change. "We're excited, but in the back of our minds, we're also a little wary," London says. "In the back of our mind, we're like, ah, that means things are warming up. So what does this mean in the long run?"

I, too, worry about the future. This year we had the hottest summer in the Northern Hemisphere.

Chris Daly, director of the PRISM Climate Group at Oregon State University, is careful to point out that the changing temperatures used for this map doesn't mean that the zone map can be used to prove global climate change, but climate change does affect what we can grow. Daly says, “Over the long run, we will expect to see a slow shifting northward of zones as climate change takes hold.”

I suppose that means the Minnesota gardening season will be longer, and I can grow zone 5 plants. However, a heating planet doesn't seem to be good for anyone, especially fragile humans.

Yet gardeners can make a difference, helping reduce carbon. According to the University of Maryland Extension, “Sustainable gardening and landscaping techniques can slow future warming by reducing carbon emissions and increasing carbon storage in soil and plants.”

It's a tiny thing in a big world, but I'll add more flowers and plants to my garden next year.

This is the opinion of Linda Larson, a St. Joseph resident. She is the author of "Grow It. Eat It," which won a national award, and "A Year In My Garden." Her column is published the second Sunday of the month.