Sow turnips in Quebec twice: in spring as soon as the soil can be worked, and again in late summer so the roots finish before hard frost. Two averages anchor the calendar, May 6 for the last spring frost and October 5 for the first fall frost, both measured at one Montreal-area station. Treat them as midpoints, not deadlines. The sections below show how to use them without getting caught out.
The short answer for Quebec
The sowing window opens around May 6, the average last spring frost, and closes in late summer at a cutoff you calculate backward from October 5, the average first fall frost. Both dates come from Environment and Climate Change Canada’s 1981-2010 climate normals for the Montreal/St-Hubert A station.
Each date is the midpoint of a spread, so neither one is a safe date. May 6 is the point where, in one year out of two, frost still arrives later. October 5 works the same way in reverse: in about half of years the first frost beats it. Plan around a window, not a day.
| Marker | What it is | How to use it for turnips |
|---|---|---|
| May 6 | Average last spring frost | Start of the spring window. A frost after this date happens in roughly half of years. |
| October 5 | Average first fall frost | The anchor for the fall crop. Count backward from it, then add a margin. |
| 152 days | Gap between the two averages | The average length of the frost-free season. A shorter year is entirely normal. |
Spring sowing
Turnips are a cool-season root and shrug off a light frost, so there is no reason to wait for a frost-free guarantee that never comes. Sowing near May 6, or earlier once the ground is workable and no longer soggy, is not late. The sticking point in Quebec is usually the soil, not the air, because ground that has just thawed can stay cold and wet well after the calendar says spring.
Late-summer sowing for a fall crop
Here the arithmetic matters. Take the days to maturity printed on your seed packet, subtract them from October 5, then pull the date back another week or two. That extra margin pays for the years when frost comes early, which is half of them. The 152 days between the two averages is the whole season on average, and a fall sowing gets only the back end of it. For the differences in how quickly varieties finish, see The Best Turnips and Rutabaga for Quebec.
What will not work here
Rutabaga seeded late is the clearest failure. It is the slower crop, and a gap of 152 days between average frosts leaves little spare time once you start the clock in late summer. A slow variety that needs most of the season will run out of it in any year that frost arrives ahead of the average.
Slow roots, short margin
Treating October 5 as a guarantee fails for the same reason. In half of years frost arrives before it, so a sowing timed to finish exactly on October 5 will be caught unripe about every other autumn. Fast turnips forgive that mistake, since a few days of lost growth cost little. Rutabaga does not forgive it.
Winter storage in the ground fails too. The mean daily minimum of the coldest month at the Montreal reference station is -14.1 °C (6.7 °F), a figure that tells you the ground freezes hard and stays that way. Roots left in the bed for harvest after the cold sets in will not come through in any reliable way, so plan to lift them before the ground locks up. The same freeze explains why late-winter sowing is a non-starter: the soil is not workable, and a seed in frozen ground is only waiting.
Borrowed calendars
An American planting chart written for a “zone 5b” garden is a poor guide here. Quebec’s hardiness zone is a Canadian rating built on seven climate variables, while the USDA system uses one, and Natural Resources Canada states plainly that the two do not convert. A Canadian zone 4a, for example, overlaps nine different USDA zones. So a Vermont or New York date lifted from an extension chart may be off by a week or more in either direction, and you would never know which.
The last trap is copying the Montreal numbers wholesale. They come from one station on the south shore, and northern or upland districts run weeks behind it. If your garden sits at altitude or well north of the St. Lawrence plain, the window above is the best case, not the typical one. The parent guide, Growing Turnips and Rutabaga in Quebec, covers the crop in general; this page deals only with timing.
What changes across Quebec
Quebec is not one garden. The hardiness zone for the Montreal reference city is 5b in the Canadian system, drawn from 1991-2020 normals by Natural Resources Canada. That rating describes Montreal, not the province, and this page does not have the spread of zones across the rest of Quebec. There is no single answer for the whole province, and anyone who gives you one is guessing.
The two sets of numbers on this page also cover different periods. The frost dates are 1981-2010 normals, while the zone rating uses 1991-2020. They are two measurements taken against slightly different backdrops, so treat them as complementary rather than perfectly aligned.
A gardener in the north or at elevation should shift both ends of the window. Spring sowing starts later, because the soil warms weeks behind Montreal’s. The fall cutoff comes earlier, because the first frost arrives sooner. Squeezing both ends shrinks the usable season, which tilts the odds toward quick turnips and away from full-season rutabaga. Build in more margin than the Montreal-based advice above, not less.
To find out where your own garden sits, open the map on Canada’s Plant Hardiness Site and look up your municipality. Do not assume your zone from a neighbor’s or from a seed catalog. Municipal lookups can differ from one town to the next, sometimes across a short drive.
Where to check this for your own county
A recommendation for your county beats one for the province, and this page is the provincial one. It rests on a single station’s averages. A local calendar rests on observations closer to your soil, your frost pockets and your elevation.
The place to start is MAPAQ, the Ministère de l’Agriculture, des Pêcheries et de l’Alimentation du Québec. The address was checked and is live, but this page has not confirmed which turnip pages sit on that site, so expect to hunt a little.
When you get there, look for two things:
- A planting calendar for your own region or regional municipality (MRC), ideally with sowing dates for root crops, not a general vegetable chart.
- Variety trials run near you, which show which turnips and rutabagas actually finished in conditions like yours.
If a regional calendar disagrees with the dates on this page, follow the regional one. It is closer to your ground.
Checking this against your own garden
Your own observations outrank every date above, because they describe the soil you actually sow into. Three things are worth watching, and none needs an instrument.
Soil by feel. Dig a handful from a few inches down. If it crumbles and feels cool, not icy, it is ready. If it smears or forms a sticky ball, wait. A bed on a south-facing slope will pass this test days before a low, shaded one, which tells you how fast your site drains and warms.
The first true leaves. The first pair after sprouting are the seed leaves. The true leaves, with their rougher, lobed edges, come next. If they take a long time to appear, your soil is colder than you assumed, and the spring window on your site starts later than the page says. If they arrive quickly, you can sow earlier next year.
Where the frost lingers. On a clear spring morning, walk the yard and note where frost still whitens the grass after the sun is up. Those low corners are your frost pockets. Write the dates down in a notebook, year after year, and your own last frost date will soon be more useful to you than a 1981-2010 average from a station on the south shore.
Some gardeners also time this by the Moon: when to plant turnips by the moon, as almanac tradition rather than fact.
Common questions
Can I sow turnips before May 6?
Yes, once the ground is workable. Turnips tolerate light frost, and May 6 is only the average last frost, with frost still possible after it in about half of years. Sow when the soil crumbles in your hand, not on a fixed date.
When is the last safe date to sow turnips for a fall crop?
This page does not give a single date, because none can be defended. Take the days to maturity from your seed packet, count back from October 5, and add a week or two for the years when frost comes early.
Does rutabaga follow the same calendar?
The anchors are the same, but rutabaga needs more of the season, so it has less room for error in a fall sowing. Choose it only if you can give it a long run before the first frost, and check the packet before you commit.
Can I use a USDA zone 5b chart for my Quebec garden?
No. Quebec uses the Canadian hardiness system, which does not convert to USDA zones. Use Canadian sources, and check the Natural Resources Canada map for your own municipality.