In Anchorage, the reference city for this page, turnips go into the ground in early to mid May, and the crop needs to be lifted before the hard freezes of late September. Everywhere else in Alaska, the dates shift. This page has frost data for one station only, so it dates one place and shows you how to adjust for yours.
The short answer for Alaska
Sow turnips outdoors from about May 3 to May 12, the span when the last spring 32°F freeze typically passes at the Anchorage station. Those dates come from NOAA NCEI 1991-2020 Climate Normals, and they describe a probability, not a calendar promise. They mark the 30 to 70 percent probability band for a 32°F freeze, so a freeze after May 12 is still possible in some years.
Turnips shrug off a light frost, which is why you do not need to wait for the band to close. Many Alaska gardeners sow as soon as the soil thaws and drains enough to rake. A bed that is still soggy or crusted with ice is a bed that rots seed.
The fall end of the window
The other bookend is the first fall freeze, September 22 to October 1 for the same station, measured the same way (the 30 to 70 percent band for a 32°F freeze). Between spring and fall sits about 143 frost-free days. That sounds generous until you remember it is a mild number by Alaska standards: Anchorage is one of the mildest inhabited parts of the state, and the Interior and the north run far shorter.
| Event (Anchorage station) | Date range | What it measures |
|---|---|---|
| Last spring freeze | May 3 to May 12 | 30-70% probability band, 32°F freeze |
| First fall freeze | September 22 to October 1 | 30-70% probability band, 32°F freeze |
| Frost-free season | About 143 days | Length between the two |
Why daylight changes the math
Long summer daylight partly makes up for the short season. Plants get many more hours of light per day than in the Lower 48, and a cool-season root crop like the turnip uses that well. Still, daylight does not warm cold soil, so germination speed in May depends on the ground, not the sun’s schedule.
Rutabaga is a different story. It wants the long end of the season, so it belongs in the first sowing, not the last. Our guide to Growing Turnips and Rutabaga in Alaska covers the crop itself, and The Best Turnips and Rutabaga for Alaska sorts out which types suit a short season.
What will not work here
Waiting for June is the quickest way to lose a rutabaga crop. A slow, large root needs most of the frost-free stretch, and with the first fall freeze arriving between September 22 and October 1, a late sowing runs out of runway before the root sizes up. Turnips forgive more, since they mature faster, but a bed sown late still gives you small roots.
Overwintering is the second failure. The mean daily minimum of the coldest month at Anchorage is 11.0°F. That is an average of the lows, not the record, so many nights run colder. Leaving roots in the ground to harvest in spring is a gamble that frozen soil and winter cold usually win. Pull them in fall and store them.
Cold soil sinks more May sowings than cold air does. A seed dropped into wet ground that has barely thawed may sit, rot, or come up patchy. If your seedlings are slow and gappy, the fix is usually patience for a week, not more seed.
Another trap is borrowing a calendar from somewhere else. Seed packets and national gardening sites print sowing advice built around spring frost dates in the Lower 48, and that advice puts turnips in the ground in March or even earlier in warmer states. In Alaska, those dates would mean sowing into frozen ground.
Likewise, the Anchorage dates on this page do not transfer to Fairbanks or to a village on the north slope. The frost-free season in the Interior and the north is far shorter, so a calendar built on 143 days will overshoot there. Treat the Anchorage numbers as a ceiling for how generous the season can be, not as an average for the state.
One more mistake is trusting a heat-driven crop plan. Heat is not the limiting factor in most of Alaska, so advice about shading turnips from summer sun or watering them weekly through dry spells belongs to other states. Here the questions are how soon the soil warms and how soon the freeze returns.
What changes across Alaska
The USDA Plant Hardiness Zone Map (2023, built on 1991-2020 normals) places Alaska in zones 1a through 8a. That is a very wide spread, and it means there is no single answer for the state. Anchorage is the reference city for this page, and other parts of Alaska differ, sometimes dramatically.
One caution on what the number means. The USDA system rests on a single variable, the average annual extreme minimum temperature. It tells you whether a perennial survives winter, which matters little for a turnip you harvest in fall. For sowing dates, frost dates and season length say more than the zone does.
If you garden north of Anchorage, or at altitude, shift your plan in two directions: the sowing date moves later, because soil thaws later, and the fall deadline moves earlier. With a shorter window, lean on quick-maturing turnips and give rutabaga a hard look before committing bed space to it. In the mildest coastal pockets, the season may stretch a little longer than on this page, though the page has no station data to say by how much.
Do not guess your own zone from a neighbor or from memory. Look up your location on the USDA Plant Hardiness Zone Map, then read it as a rough guide to how your winters compare with Anchorage’s, not as a sowing date.
Where to check this for your own county
Your state extension office is the next stop. In Alaska that is the University of Alaska Fairbanks Cooperative Extension Service, part of the land-grant extension system. Its staff work with local growing conditions every season, and they hear about what failed last year.
Two things are worth hunting for there. First, a local planting calendar for your area, ideally one that lists root crops by sowing window. Second, any list of varieties trialled where you live, since a turnip that does well in one valley can sulk in another. Alaska has boroughs and census areas rather than counties, so look for the office or publication covering your borough.
Be plain about the hierarchy: a local recommendation beats a state one, and this page is the state one. It rests on one station’s frost normals and cannot see your slope, your soil, or the lake that moderates your spring. When the extension office’s date and this page’s date disagree, go with the extension office.
This page does not carry a borough-level calendar for turnips, and it does not cite one. Rather than borrow a calendar written for another state or another crop, it points you to the people who maintain the local one.
Checking this against your own garden
Your own observations outrank every date above. Three are worth watching, and none needs equipment.
- Soil warmth by feel. Push your hand a couple of inches into the bed. If it numbs your fingers quickly, wait. A bed that feels merely cool and crumbles rather than clumps is ready, and a south-facing, well-drained spot will reach that point days before a shaded one.
- The first true leaves. After the seed leaves, the first leaves with the real turnip shape tell you how fast your seedlings are growing. Slow arrival points to cold soil or shade, which is your cue to thin carefully and consider a later sowing for the next bed.
- Where frost lands first. Note which part of the garden whitens first on a cold morning. Low spots collect cold air, so the first freeze there is your early warning for the rest of the plot.
Write the dates down for a season or two. Your notes will teach you more than any chart.
The Moon calendar is a separate, older custom: see when to plant turnips by the moon, written as tradition rather than fact.
Common questions
Can I sow turnips in June in Alaska?
You can, and quick turnips may still size up, but the page has no trial data to promise it. The first fall freeze arrives between September 22 and October 1 at Anchorage, so each week of delay trims what you harvest. Rutabaga should not wait.
Is May 3 to May 12 the date for my yard?
Only if you garden near the Anchorage station. The dates come from NOAA NCEI normals for that station, and the Interior and north have far shorter seasons. Check with your extension office for a local date.
Should I sow before the last frost?
Turnips tolerate light frost, so sowing within the May 3 to May 12 band is reasonable once the soil is workable. A freeze after May 12 remains possible in some years, so watch the forecast. Hold back if the ground is soggy or still frozen.
Can turnips stay in the ground over winter?
Not reliably. The mean daily minimum of the coldest month is 11.0°F at Anchorage, and frozen ground makes spring digging unlikely to pay off. Harvest in fall and store the roots.