There are things that come to mind when someone hears the phrase “climate change” -- warming air and oceans, more unpredictable weather, sea levels rising, ice caps melting, etc. These are all impacts of a warming world, but there are also changes closer to home, often times much closer. Maybe in your backyard.

As weather patterns change gardeners are beginning to think about how to continue planting and growing their gardens in the face of unpredictability.

Diana Alfuth is a horticulture outreach specialist with the University of Wisconsin Extension. She is also a Master Gardener and has seen the affects of climate change on gardening habits in Pierce and St. Croix counties. She outlines four areas where she has seen changes: hardiness zones, growing seasons, invasive species and the frequency of rainfall.

Hardiness zones

“Every 20 years or so the Department of Agriculture publishes a map of hardiness zones, which is based on the lowest winter temperatures,” Alfuth said. “The latest version shifted the colder zones farther north. Some areas in Wisconsin moved up a zone. That means we are able to plant and grow certain species of trees, shrubs and perennial flowers that we never used to.

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"Unfortunately, it also means that some of the plants that have traditionally been on the 'southern edge' of their comfort zone in our area will be stressed as the average temperatures rise. While it will be a slow process, we expect to lose some of our native plants to rising temperatures.”

In October 2018, Yale Environment 360 published an article that focused on hardiness zones. The author, Nicola Jones wrote:

“When that map was last updated, in 2012, nearly half the country was upgraded to half a zone warmer than it had been in 1990; in other words, all the lines shifted on average a little to the north. That was partly thanks to more detailed mapping techniques, the authors of the map reported, but also because temperatures were warmer in the more recent data set.”

Jones goes on to explain that based on current projections, studies found that hardiness zones from 2041 to 2070 will continue moving northward at a rate of 13.3 miles per decade. This will result in warmer and shorter winters and a continual flux in what can be planted and grown in Minnesota and Wisconsin.

At the planet warms the growing season will expand. Photo by Rachel Fergus/RiverTown Multimedia
At the planet warms the growing season will expand. Photo by Rachel Fergus/RiverTown Multimedia

Growing season

A warming world means that in the Midwest growing seasons are changing.

“For annual plants, which includes our vegetable gardens, the average growing season is longer than it used to be,” Alfuth said. “This means the date of the average last frost in May and the first frost in September/October are farther apart, meaning we can grow some crops that take longer to mature. … A longer growing season means we can grow some new things.”

While a longer season can mean that crops and plants grown in Minnesota and Wisconsin can be more diverse, it also means that there may be an increase in invasive species.

Margaret Smith safely removes wild parsnip, an invasive species. Smith worked with  University of Wisconsin-Extension to identify wild parsnip in the area and create a removal plan that did not require blanked spraying in Kinnickinnic township. Photo submitted by Emma Smith.
Margaret Smith safely removes wild parsnip, an invasive species. Smith worked with University of Wisconsin-Extension to identify wild parsnip in the area and create a removal plan that did not require blanked spraying in Kinnickinnic township. Photo submitted by Emma Smith.

Invasive species

Alfuth explained that invasive species will become more common as growing seasons expand.

“Both plants and insects that previously couldn’t make it through our cold winters but will now be able to survive and get established,” Alfuth said.

Experts do not have an agreed-upon hypothesis for how climate change will impact invasive species. The Invasive Species Council states that climate change will result in native species being stressed while weeds, new diseases and invasive animals will grow in population. An article published in the Smithsonian in December 2013 stated that longer growing seasons will allow more invasive species to take root (literally and figuratively). Meanwhile, the Climate Institute has stated, “It remains uncertain whether increasing concentrations of CO2 in the atmosphere will generally favor non-native plant species over native plant species.”

Despite what climate change’s impact will be on native and invasive species, gardeners can help native species by growing plants that are native to the region and those that attract and feed native insects and animals.

As climate change continues rainfall totals will become less predictable. File photo
As climate change continues rainfall totals will become less predictable. File photo

Rainfall frequency

Those who have been in southwestern Minnesota and western Wisconsin over the past few years have probably noticed the varying precipitation. Last spring many fields had barren patches where the soil was too wet to grow crops. In late September eastern Minnesota and the southwestern corner of the state are classified as “abnormally dry” or in a “moderate drought.”

“Not being able to count on our ‘average’ rainfall and rain events will make gardening more challenging,” Alfuth said.

Action steps

While the future for gardeners is unknown there are ways that individuals and communities can work to protect their gardens and help the region. The University of Maryland Extension offers suggestions that include:

  • Use “human power” in the garden instead of tools and equipment that require gas.

  • Plant trees around houses to help lessen the need to heat or cool the dwelling.

  • Compost from yard clippings and food waste helps return nutrients to the soil and reduces erosion.

  • Plant species that attract pollinators.

  • Think about grass alternatives when planting and maintaining a lawn.

Alfuth said of local gardeners:

“Be prepared for anything! They should plant trees and shrubs that are adaptable to both wet and dry periods. They should have backup irrigation available for dry spells, but that irrigation should be efficient and water saving (such as drip irrigation, soaker hoses, etc.). They should push the hardiness zones to try new plants, but also be prepared for an 'old fashioned' year that ends up damaging or killing them. They should follow the DNR’s list of potentially invasive plants and avoid anything of concern. Basically, they should keep aware of news and information that becomes available on how climate change is progressing and what the latest science is.”