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Cold Zone Gardening in Minnesota

The growing season is short, but with a little planning you can create a thriving garden
As the weather warms and the snow melts, Minnesotans rush out to their gardens and coax botanical miracles from muddy earth. Flower beds burst with color. Vegetable patches yield bushels of beans, peas, tomatoes, and zucchini. And fruit trees drip with apples and pears. 

Of course, not everyone is blessed with green thumbs. In fact, more than a few of us are all thumbs when it comes to getting a garden to produce much more than weeds. How do those prolific gardeners do it? What’s their secret sauce? The answer is more science than “saucery,” and deeply rooted in our state’s “plant hardiness zones.” If you don’t know what that is, read on, and get ready to have your best season in the soil yet.

Get to Know Your Zone

Plant hardiness zones were created by the United States Department of Agriculture (USDA) to help farmers and gardeners select plants that thrive in their region of the country. Based on seasonal temperature cycles, each zone is defined by how cold it gets in the winter. There are 13 zones in the United States, from Alaska to Florida, including Hawaii and Puerto Rico. Every zone covers a 10-F range.  

The lower the number, the colder the zone. Minnesota has five zones and they’re all pretty chill. The northern-most zone—3a—ranges from Brainerd to International Falls with average temperatures plunging -35 to – 40 F in the winter. By contrast, Fairmont, on the state’s southern border, sits in balmy Zone 5a where winter temperatures rarely dip under -15 to -20 F.

If you’re not sure what zone you’re in, visit the USDA’s Plant Hardiness Zone Map page and enter your zip code in the search bar. 

Choose Your Plants, Check for Frost, and Get Digging

Once you know your zone, you can determine which plants will thrive in your area and calculate the optimal time to get them in the ground. As a rule, you should plant after the last frost of the season. This frost-freeze calculator tells you about the average frost-free dates for your zip code. For example, in the Twin Cities area (zone 4b), there’s little chance of frost occurring after May 14. Up along the Canadian border (zone 3a), however, the last frost can come well into late May and even early June.

Whether you’re starting vegetables from seed, or shopping for perennials at the local nursey, most seeds and plants come with information about the hardiness zones where they will thrive. They also tell you about the optimal temperature ranges for healthy growth. For instance, kale and broccoli are very hardy and can go in the ground right after the last frost. But tomatoes require long, warm days, so planting might have to wait a couple weeks more until the conditions are just right.

For an exhaustive list of deciduous trees, fruit, vegetables, perennials, roses, shrubs, and other plants that can grow in each of Minnesota’s hardiness zones, visit the Minnesota Department of Agriculture’s Cold Hardiness List. 

Expand Your Zone of Learning

Of course, knowing your zone and which plants are best adapted to it is only the beginning. Each plant has unique needs for sunlight, water, soil type and fertilization. You also need to know about the various pests, blights, and diseases that can afflict your garden. Fortunately, a world of resources is only a click away. The University of Minnesota Extension has an exhaustive website covering every aspect of your Yard and Garden, from primers on trees, shrubs, vegetables, and native plants to guides on soil and nutrients, landscaping, and creating pollinator gardens. There is also an excellent resource that connects you with Master Gardeners who can answer all your questions about garden issues. The service is free, and most questions are answered within 48 hours. 

Whether you have a few potted tomatoes on the veranda, or a yard filled with carefully cultivated flowers, your garden can be a zone of peace, fun, and fulfillment. As the English poet Alfred Austin said, “the glory of gardening is hands in dirt, head in the sun, and heart with nature. To nurture a garden is to feed not just on the body, but the soul.”