Turnip seed goes into New York soil during two windows: a spring planting timed around the last frost, and a fall planting timed backward from the first freeze. Get either one off by a couple of weeks and you either lose seedlings to a late cold snap or lose roots to an early one. New York’s own frost data pins those windows down for the city, and shows exactly how much they shift once you leave it.
The short answer for New York
NOAA’s Climate Normals data, drawn from the Central Park weather station, put New York City’s last spring freeze between March 23 and April 3, and the first fall freeze between November 14 and November 27. Those aren’t hard calendar cutoffs. They mark the band where the probability of a 32°F freeze runs between 30% and 70%, meaning on March 23 there’s still roughly a 70% chance a freeze happens after that date, and by April 3 the odds have dropped to about 30%. Frost risk doesn’t vanish at either end of that window, it just gets less likely.
Turnips handle that uncertainty better than most spring vegetables, because the seedlings tolerate light frost once they’re past germination. That lets the sowing window open before the safest date rather than after it, so gardeners in the city typically get seed into the ground anywhere from early March through mid-April, using the freeze-probability band as a guide rather than a wall. Sow at the safer end of that window, closer to April 3, if a hard freeze would mean starting over; sow earlier if you’re willing to thin out whatever a late cold snap damages.
The fall sowing works from the other end of the calendar. First fall frost lands between November 14 and November 27 in the city, and turnips generally need somewhere between 30 and 60 days from seed to a harvestable root, depending on the variety. Counting back from mid-November puts the practical fall sowing window at late July through the end of August. Sow later than that and the roots are still sizing up when the first hard freeze arrives. The leafy tops may shrug it off, but a root that hasn’t finished bulking won’t catch up afterward.
What will not work here
Rutabaga, the slower cousin in this same crop family, is the first casualty of New York’s fall calendar. It typically needs closer to 90 to 100 days from seed to a mature root, not the 30 to 60 turnips need, so sowing it into that same late-July-through-August turnip window runs it past its finish line. Sow rutabaga no later than early July if it’s going in this season, and treat the turnip fall window as already too late for that particular crop.
Leaving a fall turnip crop unharvested and unprotected deep into winter is the other habit that catches New York gardeners out. The city’s coldest month averages a daily minimum of 27.9°F, a mean figure, not a record low, which means most days that month sit below freezing even at their warmest point. Turnip roots can take some cold under a few inches of mulch or snow cover, but bare soil sitting at that average minimum will freeze roots solid and split them by the time you go to dig them in January. Harvest the fall crop as it matures through late autumn, or mulch heavily once nighttime lows start running consistently in the high 20s.
A spring crop sown too early fails for a different reason entirely: not frost, but germination. Turnip seed sprouts poorly in soil colder than the mid-40s Fahrenheit, and with the region’s coldest month sitting in the high 20s for its average minimum, early-March soil in a cold year often hasn’t warmed enough yet, even on a sunny afternoon that feels like spring. Seed sown into that ground tends to sit and rot rather than sprout, which is a bigger risk to the spring planting than the last frost itself.
What changes across New York
The frost dates above describe one place: New York City, specifically the Central Park station. They don’t describe Buffalo, the Adirondacks, or the Southern Tier, and the state’s own hardiness zone range shows why. New York spans USDA zones 3b through 7b, a spread of roughly 40°F in average annual extreme minimum temperature between its coldest pockets and its mildest ones. That’s most of the USDA scale contained in a single state.
A zone 3b garden, the kind found at elevation in the Adirondacks or across the far northern counties, sees its last spring frost weeks later than the March 23 to April 3 window recorded in the city, and its first fall frost weeks earlier than November 14 to November 27. A gardener there sowing on the city’s schedule risks putting spring seed into soil that’s still effectively frozen, and fall seed into a season too short to finish a crop.
At the other end, the coastal strip nearest the ocean and the city itself sits closer to zone 7b, where winters run milder than the 27.9°F coldest-month minimum recorded there, and both frost windows push later in fall and earlier in spring than the state average suggests.
None of this means picking a date off a general map and calling it done. Check the USDA Plant Hardiness Zone Map for the zone at your own address before shifting either sowing window, and treat the city’s frost dates as a starting point to adjust from, not a schedule to copy, anywhere outside the five boroughs.
Where to check this for your own county
New York’s land-grant extension service, Cornell Cooperative Extension, publishes county-level guidance this state page can’t replicate. Every county in New York has its own CCE office, and each one adjusts planting windows for the elevation, lake effect, and microclimate specific to that county, detail no single state-wide page can carry.
Start at Cornell Cooperative Extension and look for two things once you’re on your county’s page. First, the local planting or vegetable garden calendar, built from that county’s own frost data rather than the single Central Park station used above. Second, the variety trial results or recommended cultivar lists for turnip and rutabaga, since Cornell’s regional trial programs test which varieties actually perform in that county’s soil and season length, not just which ones happen to be sold at a nearby garden center.
A county recommendation beats a state one every time, because it’s built on data closer to your own garden. This page works from one weather station and a hardiness range that spans five zones; a county extension calendar works from local station data and local trial plots. Search out your county’s Cornell Cooperative Extension office before locking in a sowing date from this page alone, especially if you garden north of the city or at any real elevation.
If a county office hasn’t published a specific turnip calendar, most still answer direct questions by phone or email, and the master gardener volunteers staffing those offices generally know the local frost pattern better than any regional average could.
Some gardeners also time this by the Moon: when to plant turnips by the moon, as almanac tradition rather than fact.
Checking this against your own garden
Every date on this page comes from a weather station average, not from your own soil. Three things your own garden tells you directly outrank all of it.
Soil warmth by feel is the first and most useful check before spring sowing. Turnip seed germinates poorly in cold, wet soil, so before sowing, push a finger a couple of inches into the bed on a morning after a few dry, sunny days. If it feels only barely cool rather than cold and damp, the soil has likely crossed into workable range regardless of what the calendar says about the last frost date.
The speed of germination and the first true leaves are the second check. Seed sown into soil that’s genuinely warm enough typically shows its first true leaves, the second set that appears after the rounded seed leaves, within about ten days of sprouting. A much slower emergence usually means the soil was colder than it felt, and the next sowing in that bed should wait longer.
The third signal matters mainly for whichever sowing lands in the hotter half of the year: bolting. A turnip that sends up a flower stalk early, before the root has sized up, is responding to a stretch of heat or day length it’s reading as a signal to reproduce rather than store energy. A bed that bolts reliably in a given month is running warmer than the regional average for that stretch, and the next sowing there should shift earlier or later to dodge it.
None of these three checks need a thermometer or a soil probe, just a few minutes of attention at the moments a sowing calendar can’t account for on its own.