Sow turnips in Ontario twice: in spring from the last two weeks of April, and again from mid-August for a fall crop. Rutabaga needs more runway, so it goes in between late May and early July. These windows come from Toronto’s frost dates, and they shift with your location.
The short answer for Ontario
The anchor numbers are Environment and Climate Change Canada’s 1981-2010 normals for the Toronto Pearson station: last spring frost on average April 30, first fall frost on average October 16. Both are mean dates. They mark the midpoint where frost is as likely to come later as earlier, so in one year out of two a frost lands after April 30, and in one year out of two the first fall frost holds off past October 16. Neither is a safe date.
That matters less for turnips than for tomatoes. Turnips are a cool-season root and shrug off light frost, which is why the April 30 midpoint works as the center of a spring window rather than a line you wait behind. Sow once the soil can be worked, then keep going into mid-May. Most seed packets list roughly 40 to 60 days to harvest, which puts spring roots in the kitchen before the worst of July.
The fall crop works in reverse. Count back from October 16. Eight weeks earlier is about August 21, so mid- to late August is the working window for turnips. Rutabaga is slower, commonly 90 days or more, and a hundred days before October 16 lands near July 8. The calendar math below is mine, built on those frost dates and typical packet maturity times, not a published Ontario schedule.
| Crop | Sowing window (Toronto-area reference) | How it is worked out |
|---|---|---|
| Spring turnips | Mid-April to mid-May | Centered on the April 30 mean last frost; soil must be workable |
| Fall turnips | Mid- to late August | About eight weeks back from the October 16 mean first frost |
| Rutabaga | Late May to early July | About 100 days back from October 16, so early July is the late edge |
For variety choices that fit these windows, see The Best Turnips and Rutabaga for Ontario. The broader picture of the crop is in Growing Turnips and Rutabaga in Ontario.
What will not work here
Start with arithmetic. From April 30 to October 16 is 169 days, the average stretch between the two frost dates at Pearson. A rutabaga sown in mid-July needs most of that remaining time and then some. It will make leaves and a thin, undersized root before the cold arrives. A late sowing is the most common way to lose the crop in Ontario.
Treating the averages as guarantees
Sowing tender crops on April 30 because it is “the last frost date” fails half the time, by definition. Turnips can take that gamble because they tolerate light frost, but a hard freeze on open seedlings in early May still happens. If you sow in the second half of April, expect to protect a row with a cover on a bad night, or to reseed a strip.
Mid-summer sowing
Sowing turnips in June or July for a “middle” crop tends to disappoint. Roots swell in heat and turn woody, strong-flavored, or run to seed, and flea beetles and root maggots are active through the warm months. The two clean windows sit on either side of summer, which is why the table has a gap in the middle for turnips.
Leaving roots in the ground all winter
The coldest month at the Toronto reference station averages a daily minimum of -10.2 °C (13.6 °F). Turnips and rutabaga are not perennial roots. Left in an unmulched bed past the hard freezes, they turn to mush or get stripped by frost heaving. Lift them, trim the tops, and store them cold and humid, or harvest through the fall as the soil allows.
One more caution: these figures describe a single station beside Lake Ontario’s urban corridor. Treating them as the number for Thunder Bay or Ottawa would be the same mistake as using Toronto’s frost dates for the whole province.
What changes across Ontario
Natural Resources Canada puts the Toronto reference city in Canadian plant hardiness zone 7a, based on 1991-2020 normals. That is the zone of one city, not of the province. Ontario spans several zones, so there is no single answer, and this page does not have the full spread to print. The Canadian system also does not convert to USDA zones; it is built on seven climate variables, and NRCan itself says there are no simple conversions.
What you can do is shift the dates the right direction. A reader in the north, or on high ground, should expect the spring window to open later and the fall window to close earlier, since northern and upland districts run weeks behind the Toronto frost dates. The fall deadline is the one that bites. Take the Pearson arithmetic (eight weeks back for turnips, about a hundred days for rutabaga) and apply it to your own local first-frost date, not October 16.
Rutabaga is the first crop to feel it. In a short northern season, it may be the one to drop or to start from transplants. Quick spring turnips hold up far better, since they need only a cool few weeks.
To find your own zone, use Natural Resources Canada’s Plant Hardiness Site and look up your municipality on the map. Do not assume the neighboring town shares your number, and do not carry a USDA zone over to it.
Where to check this for your own county
A county recommendation beats a state one, and a provincial page like this is the broader of the two. For anything local, start with the Government of Ontario’s agriculture and food pages. This page cannot confirm what is published there for each region, so check it directly.
Look for two things. The first is a local planting calendar for your area, ideally with a first-frost and last-frost date from a station near you, not the Toronto Pearson one used here. The second is any list of varieties that have been trialled in your region, since a turnip that performs in the Golden Horseshoe may sulk in a shorter season.
Keep the dates apples to apples. The Canadian frost normals cited here cover 1981-2010, while the hardiness zone uses 1991-2020. If a local source quotes a different period, expect small differences, and trust the source that is closest to your garden.
Checking this against your own garden
No date on this page outranks what your own soil is doing. Three things are worth watching, and none needs an instrument.
- Soil warmth by feel. A handful of soil that crumbles and feels cool, not cold and sticky, is ready for turnip seed. If it clumps in a wet ball, wait. Compare a sunny, sheltered bed with a shaded one: the gap tells you how much your site runs ahead or behind the average.
- The first flush of male flowers. On squash and cucumbers, male flowers show up before female ones. The date you see them is a real marker of how warm your summer is running, and a useful cue for timing the late sowings.
- The first true leaves. Seedlings first show rounded seed leaves, then the first rough, lobed true leaves. If they arrive slowly on a spring sowing, the soil is cold. If a fall sowing is slow to reach that stage, the season is running out.
Write the dates down for a year. Two seasons of notes beat any provincial average.
If you follow the almanac, here is when to plant turnips by the moon. It is a tradition, not a proven method.
Common questions
Can I sow turnips before the last frost in Ontario?
Yes. Turnips tolerate light frost, so sowing as soon as the soil is workable in mid-April is reasonable. A hard freeze on small seedlings is still possible, because April 30 is only the average last frost.
When is it too late to sow turnips for fall?
Count about eight weeks back from your first fall frost. At Pearson, with a mean of October 16, that points to around August 21. Farther north, with an earlier first frost, the cutoff comes earlier.
Is rutabaga sown at the same time as turnips?
No. Rutabaga takes about 90 days or more, so it goes in from late May to early July, not in August. It is a summer-sown crop that matures into the cool fall.
Do these dates apply to northern Ontario?
Not directly. The frost dates here come from the Toronto Pearson station, and northern or upland districts run weeks behind. Use your own local frost dates and count back the same number of days.