Manitoba can grow celeriac, kohlrabi, turnips, rutabagas, horseradish and Jerusalem artichokes, but not on one calendar. Quick, cold-tolerant roots go in as soon as the soil can be worked. Celeriac waits until after the last frost, which averages May 23 at Winnipeg. The two perennials need a permanent spot chosen before anything goes in the ground. Season length and winter cold decide the rest.
When the soil is warm enough in Manitoba
The last spring frost at the Winnipeg Richardson International A station falls on average on May 23, according to Environment and Climate Change Canada’s Canadian Climate Normals for 1981-2010. That is a mean date, not a safe one. In roughly one year out of two, frost arrives later, so treat May 23 as the middle of a window rather than a finish line. The station is also Winnipeg’s, and northern or upland districts of the province run weeks behind it. (One more wrinkle: Canadian normals cover 1981-2010, while the US figures elsewhere on this site cover 1991-2020, so don’t line them up too neatly.)
Frost is only a stand-in for what these crops want, which is warm soil. Soil lags the air. It warms after the frost risk ends, not at the same moment, and a cold, wet bed in late May can hold back a transplant that the calendar says is ready. A probe thermometer pushed a few inches (about 8 cm) down, read in the morning, tells you more than any date. For temperature thresholds that suit the crops you are growing, Manitoba Agriculture is the right place to check.
Which crops wait and which don’t
Kohlrabi and turnips tolerate cool soil and a light frost, so they can go in as soon as the bed is workable. Rutabagas, the slower cousin, are normally sown later and given the long haul to autumn. Celeriac is the opposite case. It is started indoors and set out only once the frost risk has passed and the soil has had time to warm, because a cold snap can stall it. For the basics of all these crops, see Celeriac, Kohlrabi, Horseradish and Jerusalem Artichokes.
Site the perennials first
Jerusalem artichoke is effectively permanent once planted. Every fragment of tuber left in the soil regrows, and digging the bed over tends to scatter pieces rather than remove them. It is the single most regretted planting in a vegetable garden. Choose a spot you are willing to give up for good: a fenced corner, a bed edged with a deep barrier, or a strip at the back of the property away from the vegetable rows. Horseradish behaves similarly, since root pieces left behind will sprout again, so it deserves the same forethought.
Only then comes the growing. Both go in as soon as the soil is workable in spring, well before celeriac is even hardened off. They need little attention beyond a sunny site and soil loosened to a good depth. Jerusalem artichokes also carry a plain fact about the vegetable itself: they store inulin rather than starch, and many people find them hard on the digestion. A small first portion is the sensible way to find out where you stand.
How long the season lasts here
Count the days between the two mean dates from the same Winnipeg station: May 23 for the last spring frost, September 22 for the first fall frost. That gives 122 days, or just over 17 weeks. Both dates are means from the 1981-2010 normals, so any given year can land on either side, and gardens outside Winnipeg may have less.
What does 122 days allow? A moderate window, and it settles several decisions. It supports one main sowing of the long crops and room for a second round of the quick ones. A gardener who sows kohlrabi or turnips in spring can clear the bed in midsummer and sow again for a fall harvest, because these crops tolerate light frost and so keep growing past the first frost date. A slow crop does not get that second chance. Whatever goes in for celeriac or rutabaga occupies its bed for most of the window. The succession sowing guide on this site walks through how to stagger these sowings so beds are never idle or overcrowded.
The window also settles the transplanting question. Celeriac needs nearly all of it, which makes indoor sowing the only workable route, and it is worth the trouble of checking roots at planting time. Look for circling roots in the pot, and tease them loose rather than burying a tangled mass. Set the plants out only when the soil has warmed, so that they do not sit stalled while the clock runs down.
For turnips, kohlrabi and rutabagas, the logic runs the other way. Direct sowing avoids the root disturbance that can leave misshapen roots, and the quick types do not need the head start. When the first sowing is the only one you will get, it should go in at the earliest workable date, not the most comfortable one. Giving up a week in May is cheaper than losing a week in September, when the first fall frost, averaging September 22 but sometimes earlier, can end the season for tender crops.
Heat and water in Manitoba
This page does not carry a verified count of days above 90 °F (32 °C) or a figure for summer rainfall in Manitoba, so it offers none. Guessing at them would be worse than leaving them out. What can be said honestly is what each kind of summer does. A hot, dry spell pushes kohlrabi and turnips toward bolting, and roots turn woody or pithy when watering is erratic. A cool, damp summer brings the opposite set of troubles: mildew on foliage, slow ripening, and disease in beds that stay wet. Turnips and rutabagas are brassicas, so they share their pests and diseases with cabbage, kale and mustard. A gardener who rotates them into a cabbage bed has rotated nothing. The rotation page on this site explains how to plan the sequence.
Two facts of Manitoba’s climate govern this group more than any weather forecast. The first is the season length. At 122 days between mean frosts, celeriac, the long one, can finish only if it is started early indoors and kept growing steadily. Whether it finishes in your garden depends on the variety and on your local conditions, which is a question for the provincial trials.
The second is winter. The mean daily minimum of the coldest month at Winnipeg is -21.4 °C (-6.6 °F), an average that hides colder nights. Natural Resources Canada places Winnipeg in Canadian hardiness zone 3b, a system that does not convert to a USDA zone, because it weighs seven climate variables rather than one. In practice, horseradish and Jerusalem artichokes, being perennials, can stay in the ground under a layer of mulch. Celeriac, kohlrabi, turnips and rutabagas are lifted and stored before the soil freezes.
Storage touches food safety, so inspect before you trust. Look over every root for soft patches, weeping spots or a moldy crown. Any of those ends the question for that root, and a root that merely looks sound is not thereby safe. Nothing here promises a keeping time, because conditions vary too much to promise one. Check stored roots regularly, remove any that have turned, and do not let one bad root sit against the others.
Which these root crops suit Manitoba
Choose by type, and let the climate sort them. A season of 122 days between mean frosts favours the earliest types: quick kohlrabi and turnips that mature before the fall frost. A damp summer makes disease resistance the first criterion for brassicas. A hot, dry one rewards mulch to shade the root zone and keep moisture even. The table sets out how each type fits.
| Type | Fit for Manitoba | What to watch |
|---|---|---|
| Kohlrabi, turnips | Good: quick, tolerate cool soil and light frost, allow a second sowing | Bolting in heat, brassica diseases |
| Rutabagas | Reasonable: slower, use most of the season | Brassica diseases, steady moisture |
| Celeriac | Demanding: the long crop, needs an early indoor start | Cold snaps after planting, uneven watering |
| Horseradish | Good: hardy perennial, overwinters under mulch | Spreads from root pieces left in the soil |
| Jerusalem artichokes | Good: hardy perennial, but permanent once planted | Siting, digestive tolerance |
Horseradish asks for care at the kitchen end. Grating a fresh root releases compounds that burn the eyes and airways. Work with the window open or the fan on, keep your face well back from the bowl, and do not treat it as a joke. Fresh-grated horseradish can leave a person coughing.
This page names no varieties, and that is deliberate. A cultivar that thrives in another province or state tells you nothing about a Manitoba garden, and an invented name is the one error a gardener spots at once. The only recommendation that means anything is a variety trialled locally, and this page does not have those results. Manitoba Agriculture is the place to ask. Gardeners comparing climates can also read Growing Unusual Root Crops in British Columbia and Growing Unusual Root Crops in South Dakota, though neither stands in for local trial results.
Common questions
Is May 23 a safe planting date for celeriac?
No. It is the mean last spring frost at the Winnipeg Richardson International A station, so in about one year out of two, frost comes later. Wait until the soil has warmed too, and check how your district compares with Winnipeg.
Can celeriac finish a season in Manitoba?
The 122 days between the mean frost dates leave little room for the longest crop, so it needs an early indoor start and steady growth. Whether it finishes depends on the variety and your site, so ask Manitoba Agriculture which ones have been trialled.
Where should Jerusalem artichokes go?
Somewhere you can leave for good. Every tuber fragment left in the soil regrows, so a fenced corner or a bed with a deep barrier works better than a spot in the middle of the vegetable rows.
How do I know a stored root is still usable?
Inspect each one. A soft patch, a weeping spot or a moldy crown ends the question, and looking sound is not proof of safety. Discard any root that fails, and check the rest regularly.