Parsnips, rutabagas, celeriac, salsify, scorzonera, horseradish and Jerusalem artichokes are the safe bets in Minnesota. Cold is what they are built for, and the state supplies plenty of it. Tropical roots such as oca, yacon and ginger are the ones that struggle. Two numbers do the sorting: how late the spring freezes run and how early the autumn ones arrive.
The short answer for Minnesota
Choose by type, and let the frost window and winter cold decide. For the Twin Cities, NOAA’s 1991-2020 Climate Normals put the last spring freeze (32°F) between April 17 and April 30. The first fall freeze falls between October 11 and October 23. Those are probability bands, the 30 to 70 percent range for a 32°F freeze, so they are odds, not promises. A freeze after April 30 is still possible, and one before October 11 is too.
The same data gives a mean daily minimum of 8.8°F in the coldest month, measured at the Minneapolis reference station. That is the figure that decides whether a root can stay in the ground over winter. This page has no summer heat figure, so the advice below leans on frost dates and winter cold alone.
| Type | Examples | Fit for Minnesota |
|---|---|---|
| Hardy perennials left in the ground | Jerusalem artichoke, horseradish | Strong. Built for cold winters and dug in fall or early spring. |
| Cool-season roots sown or set out in spring | Parsnip, salsify, scorzonera, celeriac, rutabaga | Strong. Tolerate frost and sweeten in cold soil. |
| Quick roots sown in late summer | Daikon, black radish, turnips | Good. Finish before the hard freeze. |
| Frost-tender, long-season roots | Oca, yacon, ginger, sweet potato | Poor outdoors. Container or indoor projects. |
The second row is where most Minnesota gardeners should put their effort, because those roots reward patience. Parsnips and salsify need a long stretch in the ground and germinate slowly in cold soil, so the early spring sowing is the one that counts. Celeriac is usually started indoors and set out as a transplant. Our guide to When to Plant Unusual Roots in Minnesota works through the timing in detail.
The first row is the easiest. Plant a horseradish crown or a few sunchoke tubers once and they come back every year. Sunchokes in particular spread hard, so give them a corner you can afford to lose.
What will not work here
Anything that needs a full tropical season. Oca forms its tubers as days shorten in fall, which is exactly when a Minnesota freeze arrives. Yacon and ginger want months of steady warmth, and the first fall freeze can land as early as October 11 even in the mild Twin Cities. A tender root planted after the last spring freeze risk has passed, then cut down in mid-October, never gets the runway it needs.
Northern Minnesota makes this worse. The Twin Cities are the mild south, and the north runs two to three weeks tighter at both ends of the season. Spring freezes push well into May, and autumn ones come noticeably earlier. A slow crop that barely finishes in Minneapolis will not finish near the Canadian border.
Late sowing of the slow hardy roots fails too. Parsnips and scorzonera sown in early June, after a gardener waits for “real” warm weather, run out of season. Cold soil does not hurt them nearly as much as lost weeks do. Sow them as soon as the ground can be worked, accept a patchy first week of germination, and keep the seedbed moist.
Winter creates its own failures. A mean daily minimum of 8.8°F in the coldest month means the worst nights run colder still. Shallow, unmulched roots in bare soil can heave out of the ground in repeated freeze and thaw. Marginally hardy perennial roots can also die in an exposed bed with no snow cover. Parsnips left for spring harvest do best under a thick layer of straw or shredded leaves, and the mulch should go on before the ground freezes hard.
One more mistake is copying a warmer state’s calendar. A guide written for Missouri or the Carolinas assumes a spring that opens weeks earlier and an autumn that closes weeks later. Following it here leaves you sowing into cold mud and harvesting into frozen ground.
What changes across Minnesota
Minnesota is not one garden. The USDA Plant Hardiness Zone Map (2023, built on 1991-2020 normals) places the state in zones 3a to 5a. That range covers three whole zone numbers, so there is no single answer. The system rests on one variable only, the average annual extreme minimum temperature. It says nothing about season length, summer warmth or how wet your soil is in April.
For dated advice, this page uses the Twin Cities as its reference point, since the frost bands above come from that station. Other parts of the state differ, and the further north you go, the more the Twin Cities figures should be treated as a best case. I will not tell you which zone you are in. Your own location on the USDA map settles that, and the map is searchable by ZIP code.
A reader in the north should shift three things. Sow spring roots later, in line with the two to three weeks of added cold at the front end. Favor shorter-maturity types: rutabaga, turnips and fall radishes finish faster than celeriac. And lean harder on perennials like horseradish and sunchokes, which do their growing on a schedule of their own.
Minnesota has no mountain range to speak of, so latitude does most of the shifting. Local features still matter. A low spot where cold air pools can hold frost days longer than a nearby slope, and a bed against a south-facing wall warms sooner. See Growing Unusual Root Crops in Minnesota for how those site differences play out across a whole garden.
Where to check this for your own county
Your state extension service is the next stop. University of Minnesota Extension is the land-grant program for the state, and its staff and Master Gardener volunteers work from local trial plots and county experience rather than a statewide average.
Look for three things there. First, a local planting calendar for your county or region, with sowing windows tied to frost dates for your area. Second, the vegetable varieties that have been trialled near you, which tell you which parsnip or rutabaga types have actually performed in your kind of season. Third, any root crop guidance for horseradish, parsnips and the like, plus soil testing information if your beds are heavy or stony, since forked roots usually signal a soil problem.
A county recommendation beats a state one, plainly. This page is the state one. It rests on a single reference station in the mild south, and a grower in the northern counties could follow it faithfully and still be two weeks off. This page also does not have a county-level root crop calendar from Extension, so it does not invent one.
Checking this against your own garden
Your own observations outrank every date here. Three are worth watching, and none needs an instrument.
Soil warmth by feel. Push your bare hand a few inches into the bed. If the cold makes your fingers ache within a minute or so, the soil is too cold for slow germinators to move quickly. Beds that pass this test earlier than your neighbor’s are warmer microclimates, usually because of sun exposure, drainage or a nearby wall.
The first true leaves. On an early parsnip or salsify sowing, the first true leaves, the ones that look like the adult plant after the seed leaves, show how fast your site is moving. If they appear well ahead of the calendar, your garden runs warm. If they lag, plan for the slower end of the range.
The first flush of male flowers. Squash and cucumbers produce male flowers before female ones. When they show up in your garden, warm weather has truly settled in. Note the date each year, and use it to time your late-summer sowing of daikon and fall radishes against your own season.
Keep a few written dates for a couple of seasons. They will teach you more than any statewide map.
Common questions
Can I grow ginger or yacon outdoors in Minnesota?
Not as a reliable outdoor crop. Both need a long, frost-free season that Minnesota does not provide, even in the Twin Cities where the first fall freeze can arrive as early as October 11. Treat them as container plants you can bring indoors.
Will parsnips survive a Minnesota winter in the ground?
Parsnips are hardy and can be left in the ground for a spring harvest, but a thick mulch of straw or leaves protects them. With a mean daily minimum of 8.8°F in the coldest month, bare soil is a gamble. Dig what you will not use until the ground thaws.
Are Jerusalem artichokes safe to plant?
They are very hardy and come back year after year, which is the problem. Plant them where spread will not bother you, and dig every tuber if you ever want them gone.
Should I use the Twin Cities dates if I garden in northern Minnesota?
Use them as a starting point only. The north runs two to three weeks tighter at both ends of the season, so expect later spring sowing and an earlier autumn freeze. Check University of Minnesota Extension for guidance closer to your county.