The Best Unusual Roots to Grow in North Dakota

The best unusual roots for North Dakota are the ones that tolerate deep cold and don’t need a long, hot summer: horseradish, Jerusalem artichokes, parsnips, salsify, scorzonera, celeriac started indoors, and daikon radish sown late. Sweet potatoes, yacon and oca are experiments. The reasons come down to a short frost-free window and a very cold winter.

The short answer for North Dakota

Sort your options by type. Hardy perennial roots come first, because they never depend on the frost-free window. Frost-tolerant biennials come second, since a light freeze in fall doesn’t hurt them. Anything that wants a long, hot summer comes last, and you should treat it as a gamble. This page has no summer heat or growing-degree-day figures for the state, so the sorting rests on season length and winter cold alone.

The season figures come from NOAA’s 1991-2020 U.S. Climate Normals. Each date range is a probability band. The last spring frost is listed as May 4 to May 15, which is the stretch where the chance of a 32°F freeze falls between 30 and 70 percent. The first fall frost runs September 25 to October 5 on the same basis. These are reference-city numbers from an airport weather station, not a state-wide promise. Rural and suburban gardens usually see the last spring frost later and the first fall frost earlier, often by one to two weeks.

Count from the spring window to the fall window and you get roughly 130 to 155 days. Trim a couple of weeks off that for a rural plot and you see the problem. Winter is the other number. The mean daily minimum of the coldest month at the Fargo reference station is 0.2°F. That figure decides what survives in the ground, and it favors roots that evolved for cold.

For the wider picture of how these crops behave, start with Growing Unusual Root Crops in North Dakota. When you buy seed, pick the shortest days-to-maturity listed for each crop. That number matters more here than any cultivar’s reputation.

What will not work here

Yacon is the clearest failure. It wants most of a long season to build its storage roots, and a first fall frost between September 25 and October 5 ends the season well before it finishes. Oca is a similar story. It forms its tubers late, as days shorten, and frost often arrives first. You can start either indoors, but the gap between the end of the season and the plant’s needs doesn’t close.

Ginger and turmeric won’t finish outdoors either. Sweet potatoes are the borderline case. They can produce small harvests in a warm pocket under black plastic, but a slip planted in cold soil just sits there. Because the spring window is a 30 to 70 percent band, a freeze after May 15 is still a real possibility, and tender slips don’t forgive it.

Cold soil also sinks early sowing of the slow roots. A parsnip seed sown on May 4 into soil that hasn’t warmed can sit for weeks before it sprouts, and the crust that forms in the meantime stops seedlings from emerging. Parsnips, salsify and scorzonera all need a full season to size up, so gardeners feel pressure to sow as early as possible. Sowing when the soil is workable but still cold gains nothing if germination stalls. Keep the seedbed evenly moist, and expect slow emergence.

Celeriac has its own trap. Direct-sowing it is hopeless here, since it needs a long start, and transplants that get a cold snap can bolt instead of bulbing. Start it indoors and harden it off carefully. Don’t set it out until the frost band has clearly passed.

Winter breaks a different group. With a coldest-month mean minimum of 0.2°F, roots left in the ground without mulch can freeze solid and turn to mush, and a thaw-and-refreeze cycle can push shallow roots upward. Parsnips are famously sweeter after frost, but that advice assumes mild winters. Here, either dig them before the ground locks up or cover the bed with a deep layer of straw or leaves. Jerusalem artichokes shrug off the cold, so what fails there is containment. A few tubers left behind become a patch.

This page has no state figures for summer heat or rainfall, so it doesn’t rule anything out on those grounds. What it can say is that the failures above follow from the season length and the winter minimum alone.

What changes across North Dakota

The USDA Plant Hardiness Zone Map (2023, built on 1991-2020 normals) puts North Dakota across zones 3a to 4b. That spans four half-zone steps, so there is no single answer for the state. A garden at one end of that range faces a harsher winter than one at the other, and they won’t make the same choices.

One limit on the zone system matters here. It rests on a single variable, the average annual extreme minimum temperature. It tells you whether a perennial survives winter. It says nothing about how long your summer lasts. Two gardens in the same zone can have frost dates two weeks apart, and the second number is the one that decides whether a parsnip or a celeriac finishes.

If you’re in the colder north of the state or on higher ground, shift your plan in three ways. First, lean harder on the hardy perennials, horseradish and Jerusalem artichoke, which don’t care about the season. Second, drop celeriac and any warmth-demanding tuber, and favor the shortest-maturity parsnip and radish types. Third, mulch earlier and deeper, since the ground freezes sooner and harder.

In the milder southern and eastern parts, and in sheltered spots near buildings or south-facing walls, you have a little more room. A gardener there might try celeriac or a small sweet potato bed under black plastic. But a warmer pocket is still a short-season garden by national standards, and the 130-to-155-day figure stays the planning limit.

I won’t tell you which zone you’re in, because a state page can’t know. Look up your location on the USDA map, which lets you search by ZIP code, and compare what it says to the range above.

Where to check this for your own county

The right next stop is NDSU Extension, the state’s land-grant extension service. Look for two things there. The first is a local planting calendar or frost-date table for your county, because the figures on this page come from one reference city and your garden almost certainly differs from it. The second is any listing of vegetable varieties trialled near you. A cultivar that performed well at a research plot in your part of the state is better evidence than a seed packet’s claims.

A county recommendation beats a state one, and this page is the state one. It tells you which types of roots suit the state’s short season and cold winters, and it can’t see the lake effect, the river valley, the shelterbelt on your north side, or the low corner where cold air pools. Your county extension office can, or at least it knows the region’s patterns.

Once you have your local frost dates, our guide on When to Plant Unusual Roots in North Dakota shows how to turn them into sowing and transplanting dates. If your local numbers differ from the ones above, trust yours.

Checking this against your own garden

Your own observations outrank every date printed here. Three are worth watching, and none needs equipment.

Soil warmth by feel. Grab a handful of soil from planting depth and hold it in your bare palm for a minute. If it still feels cold, germination of parsnip and salsify will stall. Try this in several spots. The bed beside a south wall will warm days before an open bed, and the difference maps your microclimate.

First true leaves. Seedlings first show rounded seed leaves, then the true leaves with the plant’s characteristic shape. How quickly radishes or early beets reach that stage tells you how fast the soil is warming. If they linger, your garden runs cold and slow, and the long-season roots will need extra help.

The first male flowers. On squash and pumpkins, male flowers open before the females. Their arrival shows that real summer warmth has reached your plot. If they come late, you probably have a short season, so plan for early-maturing roots and a firm fall harvest date.

Write down what you see, with dates, for a couple of seasons. A garden notebook is worth more than any reference station.

Common questions

Can I grow sweet potatoes in North Dakota?

You can try, but it’s a gamble. With a first fall frost between September 25 and October 5 at the reference city, and earlier in many rural gardens, the harvest is often small. Black plastic and a warm spot help.

What is the easiest unusual root for a beginner?

Horseradish. It’s hardy through North Dakota winters, needs little attention, and doesn’t depend on the length of the season. Plant it where you can keep it contained.

Do parsnips need to stay in the ground over winter?

No. Frost sweetens them, but with a coldest-month mean minimum of 0.2°F at Fargo, unprotected roots can freeze hard. Dig them before the ground locks up, or mulch deeply.

Are Jerusalem artichokes hard to grow here?

No, the cold doesn’t trouble them. The difficulty is that they spread, and tubers left in the soil will resprout the next year. Give them their own bed, and dig carefully.