Start with fast, small-rooted turnips. Rutabaga is the gamble. It can work where the frost-free season runs about 143 days, as it does in Anchorage, but the slowest types lose that bet farther north or higher up. Everything below hangs on that number, and on how quickly it shrinks once you leave the Anchorage area.
The short answer for Alaska
Those 143 days are a count, not a promise. In the NOAA 1991-2020 Climate Normals for the Anchorage station, May 3 to May 12 is the band where the chance of a last 32F spring freeze sits between 30 and 70 percent. The first fall 32F freeze falls September 22 to October 1 on the same terms. Both are probabilities of a freeze, not guaranteed dates, so a cold night can show up on either side of them.
Turnips and rutabaga are cool-season roots that tolerate light frost. That lets you sow close to the spring band and keep harvesting a little past the fall one, which helps in a short season. Long summer daylight also makes up part of the gap, since plants keep photosynthesizing through hours that a Lower 48 garden never gets. The decision comes down to root type, matched to how many days you can actually give the crop.
| Type | Fit for an Anchorage-length season | How to use it |
|---|---|---|
| Quick salad turnips (small, white, Japanese-style) | Strong | Sow in succession, eat young, and expect a harvest well inside the season |
| Globe turnips for fall storage | Good | Sow so the roots size up in cooling weather, then pull before hard freeze |
| Rutabaga | Workable but tight | Sow at the earliest sensible date and choose the earlier-maturing selections |
The seed packet is your best filter. Find the days to maturity, count that many days back from the fall freeze band, and you have your latest sensible sowing date. If you want the dates worked out week by week, When to Sow Turnips in Alaska does that, and the parent guide, Growing Turnips and Rutabaga in Alaska, covers the basics of culture.
One caveat. This page’s figures describe Anchorage, which is among the mildest inhabited parts of the state. The Interior and the north are far shorter, and the page does not carry frost dates for them.
What will not work here
A late-sown, slow rutabaga is the clearest loser. A big storage-type root needs most of that 143-day window, and the frost-free season is only a ceiling. Sow in mid-June and you are asking it to bulk up while the days shorten and the fall freeze band (September 22 to October 1) approaches. You will get leaves, a woody neck and a root the size of a golf ball.
Overwintering in the ground fails too. The mean daily minimum of the coldest month at the Anchorage reference station is 11.0F. That is an average of the nightly lows, so actual nights go colder. Turnips and rutabaga are not built to sit through that, and the mild-winter habit of leaving roots in the row to harvest as needed belongs to other states. Pull them before the ground locks up, then store them cool.
Heat is the usual enemy of turnips elsewhere, and it is not the problem here. The Anchorage numbers describe a cool summer, so a fixed weekly watering schedule copied from a hotter state can leave a bed sodden. Water when the top inch of soil is dry, and let the weather set the pace.
Sowing into cold, wet soil on the first warm afternoon is another trap. Seeds can sit and rot, and young plants hit by prolonged cold may bolt rather than form a root. The spring band is a probability, so a seedling that emerges in the first week of May can still see a freeze. Cover the bed or hold your second sowing back a week or two.
Cool, damp conditions also favor the root maggot that attacks brassicas in Alaska gardens, and turnips and rutabaga are brassicas. Bare, uncovered rows can end up with tunneled roots by August. Floating row cover, put on at sowing and kept tight to the edges, is the standard defense, though your local extension office can tell you how bad the pressure is where you live.
What changes across Alaska
On the USDA Plant Hardiness Zone Map (2023 edition, built on 1991-2020 normals), Alaska runs from zone 1a to 8a. There is no single answer for the state. A zone number is built on one variable only, the average annual extreme minimum temperature, so it tells you whether a perennial survives winter. It says nothing about how many frost-free days you get, and that count is what matters for a root you harvest in one season.
That is why the Anchorage figures here are a reference point, not a state average. The Interior and the north have far shorter seasons, and altitude shortens them further. Long daylight offsets some of the loss, but it does not rescue a slow variety.
If you garden north or high
Shift toward speed. Put quick salad turnips first and treat rutabaga as an experiment in a small bed, not a staple. Sow the day the soil can be worked and the seedbed is not waterlogged, and think about raised beds or a south-facing spot that warms sooner. Row cover does double duty, since it blocks root maggots and takes the edge off a cold night. Count your own days to maturity against your own fall freeze, because the Anchorage band will not apply.
Farther south and near the coast, the question is less about freeze and more about soil temperature. Cool ground can slow germination well past the date a seed packet suggests.
Which zone you fall in is not something this page can tell you. Look up your location on the USDA Plant Hardiness Zone Map and read your zone there. Then check it against the frost-free days your local extension office publishes, because the two numbers answer different questions.
Where to check this for your own county
A county recommendation beats a state one, and this page is the state one. Alaska is organized into boroughs and census areas, but the point stands. Someone who has watched turnips grow in your area for years will know things a statewide summary cannot, such as whether late-August frost visits your valley or your neighbors’ south-facing slope.
Start with the University of Alaska Fairbanks Cooperative Extension Service, the state’s land-grant extension system. When you get there, look for two things.
- A local planting calendar for your area, with sowing dates for cool-season root crops, not just a statewide table.
- Varieties trialled near you, ideally in a similar growing season, with notes on which turnips and rutabagas finished in time.
Extension calendars are often written crop by crop, not for vegetables in general. If you find one for cabbage or radish and none for turnip, note which crop it covers and do not assume the dates transfer. This page does not cite an Alaska-specific turnip calendar or variety trial, so it cannot hand you one. A local office can say what is published for your area or point you to a Master Gardener who knows.
Call or email if the website does not answer your question. Extension staff can tell you your area’s typical frost dates, what the root maggot pressure looks like, and whether anyone has grown rutabaga to a decent size locally.
Checking this against your own garden
Your own bed outranks every date on this page. Three observations cost nothing and need no instruments.
First, feel the soil. Push your hand a few inches into the bed in the morning. If it is cold enough to ache and clings in a wet clod, wait on direct-sowing. If it crumbles and feels cool rather than cold, you are close. A bed against a south wall or in raised boxes will usually reach that point days before open ground, and the gap tells you which spot to use first.
Second, watch the first true leaves. After seeds sprout, the first pair are seed leaves. The first rough, shaped leaves come after. If that stage takes weeks, the soil or the air is running colder than the planting date assumed. If it comes quickly, your microclimate is warm and you may be able to sow earlier or in succession.
Third, record the date of the first frost you see on your own plants, such as a white crust on leaves or a stiff, dark patch on tender seedlings. Compare it with the September 22 to October 1 band. Do it for a few years and you will know whether your bed sits in a cold pocket (frost arrives early) or a sheltered one (it holds off).
Common questions
Can I grow rutabaga in Anchorage?
Yes, with about 143 frost-free days it is workable, but the margin is thin. Sow early, choose selections suited to short seasons, and protect the bed from root maggots. Farther north, treat it as an experiment.
Which should I plant first, turnips or rutabaga?
Turnips. They finish sooner, and a small early crop shows you how your soil and season behave before you commit space to the slower root.
Can I leave turnips in the ground over winter in Alaska?
Not reliably. The mean daily minimum of the coldest month at the Anchorage station is 11.0F, and nights run colder than that. Harvest before the ground freezes and store the roots cool.
When is it too late to sow?
Count back from your fall freeze: the Anchorage band is September 22 to October 1. If the days to maturity on the packet would carry the roots past it, sow a faster type instead. Roots will bulk up a little after a light frost, but a slow variety sown too late will not catch up.