Generally — Most Areas
sweet potato (zones 3-11) suits most of Alaska (1a-9a) — zones 3-9 are in range, and the rest of the state is the exception.
Sweet Potato in Alaska — the short answer
Sweet Potato in Alaska: hardy in zones 3–11, full sun, against a state median of ~147 frost-free days.
- Plant zones
- 3-11
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Alaska zones
- 1a-9a
- USDA PHZM 2023
- Frost window
- Apr 16 - May 15 – Sep 24 - Oct 29
- NOAA RCC ACIS 1991-2020, 28°F
- Shortest county season
- 85 days
- NOAA Regional Climate Centers ACIS station record, 1991-2020, county 28°F killing freeze
- Days to maturity
- 110 days
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — per-field provenance varies and is published with the dataset.
Your yard isn't the whole zone.
Sweet Potato is grown as an annual, so your winter zone isn't the deciding factor — your frost-free window is. A typical Alaska site runs ~147 frost-free days, but that is a state median, not your yard: slope, trees, and low spots move the last-frost date across a single parcel. Enter your address and we'll score sweet potato against your land's actual frost dates, sun, and soil.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
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Alaska is not one climate
A single Alaska answer averages 28 counties whose growing seasons are 155 days apart — from 85 frost-free days in Southeast Fairbanks County to 240 in Sitka County. Which end of that your land sits nearer changes what sweet potato can finish before the first hard freeze.
The middle half of 28 counties runs 118–196 days, with a median of 145 days — a 155-day span end to end.
Measured across 28 Alaska counties. NOAA Regional Climate Centers ACIS station record, 1991-2020, county 28°F killing freeze. Quartiles are order statistics — every figure shown is a value a real county recorded, not an interpolation. Your own site sits somewhere inside this range; a parcel report resolves where.
Where in Alaska Fits Best
Even within Alaska's zones 1a-9a, county microclimates differ enough to change what thrives. These counties carry the closest zone match for sweet potato (USDA PHZM 2023):
Zone Comparison
Sweet Potato Needs
- USDA Zones: 3-11
- Frost-Free Days: 80+
- Sun: Full Sun
- Mature size: 1 ft tall
- Picking window: ~30 days of harvest
- Drought tolerance: High
Alaska Has
- USDA Zones: 1a-9a
- Last Hard Freeze (28°F): Apr 16 - May 15
- First Hard Freeze (28°F): Sep 24 - Oct 29
- Annual Rainfall: 10-160 inches
- Common Soils: Permafrost, Glacial silt, Volcanic ash
Plant Zone Range (zones 3-11)
Preferred Soil pH
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS, and university Extension sources — per-field provenance varies and is published with the dataset. State data: USDA ARS PHZM 2023, NOAA Climate Normals, NRCS SSURGO.
When to Plant Sweet Potato in Alaska
The frost window
Across Alaska, the last spring hard freeze (28°F) clears between Apr 16 and May 15, and the first fall hard freeze lands between Sep 24 and Oct 29 (NOAA Regional Climate Centers ACIS, 1991-2020). Counting from the latest last freeze to the earliest first freeze, that's a 132-day window you can count on — up to 196 days on a mild site in a kind year. That marks the hard freeze, not the last light frost, so tender transplants usually wait another 2-3 weeks.
Frost tenderness
Sweet Potato is frost-tender — FAO ECOCROP puts its killing temperature at 41°F — so set plants out two to three weeks PAST your local last hard freeze, not on it and not on the state's earliest date. The 28°F marker above is when killing freezes stop, not when light frost does. That is the point where cold damages growing tissue, not a winter-survival floor — an established perennial comes through far colder while dormant, which is what its hardiness zone tells you.
When to start the seed
Those dates are when sweet potato goes out, not when it starts. It is sown under cover about 8 weeks ahead, so counting back from Alaska's late-side last freeze of May 15 is what fixes your sowing date — and a yard that clears frost earlier than the state's late date starts earlier still.
Days to maturity vs. the window
At 110 days to maturity (Growable Ground Plant Database), one crop fits Alaska's 132-day dependable window with 22 days of margin — plant at the front of the window to keep that cushion.
Timing tuned to sub-state frost dates — North Slope County, not the statewide average.
Frost window: NOAA Climate Normals 1991-2020. Plant timing fields: Growable Ground Plant Database — frost-free days from FAO ECOCROP, days to harvest from university Extension production guides, and growing-degree-day and chill-hour minimums that are compilation estimates rather than published figures. Your site's own frost dates can run earlier or later than the state range — a parcel report pins them down.
Growing Season Fit
The zone check says sweet potato survives winter in part of Alaska, not across all of it. Whether the season is long enough — and warm enough — is a different question.
Frost-free days
Sweet Potato wants 80+ frost-free days; a typical Alaska site sees ~147 (NOAA Regional Climate Centers ACIS station record, 1991-2020). That leaves comfortable headroom for succession planting.
GDD and chill-hour figures are computed from PRISM 1991-2020 monthly climate normals; frost-free days from NOAA Regional Climate Centers ACIS station record, 1991-2020. Each is the state median across its counties (P25/P75 span the within-state spread). Hardiness-zone range is USDA PHZM 2023.
Soil + Drainage Fit
Sweet Potato tolerates a wide pH range (pH 4-8.7) — 4.7 units, acid ground through alkaline — so soil acidity is rarely what limits it in Alaska. A soil test is still worth having, but for what else it tells you about this site, not to clear this plant. It will grow across that whole span, but it does best between pH 5 and 7 — worth knowing before you decide whether a Alaska soil test result is a problem or just a number.
Your land, not the state average
Whether sweet potato is safe to eat from Alaska soil is a block-by-block question, not a town-wide one — 15,895 documented contamination sites mean levels spike on some parcels and not the one next door. Sweet Potato roots to about 19 inches, so it is the top 19 inches under your address that decide what it takes up, so only a test on your address settles it.
Check your parcel → Source: USDA NRCS SSURGO + EPA/state contamination databases.
Plant pH requirements: FAO ECOCROP and USDA PLANTS, with the remaining rows from other published sources or Growable Ground compilation. Drainage: FAO ECOCROP, with the remaining rows from other published sources or Growable Ground compilation. Alaska soil profile from USDA NRCS SSURGO. Site-specific verification: a 30-minute soil test from your local Extension lab.
Before you plant sweet potato for food
Anything you grow to eat takes up what is in the ground it grows in, so what is on record near you is worth knowing before sweet potato goes in. What follows is Alaska’s documented federal record at state scale — a screening signal, not a soil test, and not a statement about any one lot.
Safe to Grow Here?
What the federal record shows across Alaska — and how to grow with it.
We checked the federal record across Alaska — 15,895 documented sites across 7 of the 9 source types we track.
The most significant on record: 281 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
Alaska carries one of the heavier federal records we track — and that's not a verdict on your yard. Proximity to a documented site is information, not a diagnosis: nothing here says any particular parcel is affected. It does earn one concrete step — before food beds go in the ground, a professional soil test tells you exactly what you're working with, and raised beds with clean imported soil grow well almost anywhere in the meantime.
Severity Distribution
across Alaska
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Alaska, two things run higher than the national average across Alaska — Mining (5,812 sites) and Superfund (281 sites). It's not cause for alarm — it's worth knowing, and there's a sensible way to grow around it.
Mining: Mining sites — both historic and active — can leach heavy metals (arsenic, lead, cadmium, mercury) into soil and water for centuries after operations cease.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test soil for heavy metals (lead, arsenic, cadmium, mercury) — this is essential near any mining site.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What Else to Consider for Sweet Potato in Alaska
Zone compatibility tells you about winter cold survival — but Alaska growers also need to think about:
Extremely short growing season (70-110 frost-free days)
Permafrost prevents deep root growth in many areas
Limited soil development in glacial terrain
Growing sweet potato here specifically
Because you eat the root of sweet potato that sit in the soil, contamination matters more than for most crops — Alaska has 15,895 documented sites, and lead concentrates block by block, not town-wide.
Test your soil for lead first, and raise sweet potato in clean imported soil if the reading is high. How to handle it →
What to actually do about these — and the constraints that apply to every Alaska grower, not just sweet potato — is covered on the Alaska growing guide.
Timing shifts within Alaska
Alaska isn't one climate. In North Slope County, the last hard freeze (28°F) holds until about Jun 7 — roughly 33 days later than the recorded state median — so plant sweet potato to your county's window, not the statewide date.
Sweet Potato needs about 80 days of frost-free season to complete its cycle. Even Southeast Fairbanks County — Alaska’s shortest season at 85 frost-free days — clears that by 5 days, so season length isn’t the constraint anywhere in Alaska. What varies is your own parcel.
Across Alaska’s 28 counties the frost-free season runs from 85 days in Southeast Fairbanks County to 240 days in Sitka County — a spread of 155 days, which is why a single statewide planting date misleads. The median Alaska county sees 147 frost-free days, leaving sweet potato about 67 days of slack on a typical parcel — room for a second sowing where the season runs long.
County last-freeze dates and frost-free day counts: NOAA Regional Climate Centers ACIS (1991-2020), county 28°F freeze (earlier than the folk 32°F "last frost"). Sweet Potato's 80-day requirement: USDA PLANTS / Growable Ground plant database (minimum frost-free days). A parcel report resolves your address's own frost dates.
Pollinator + Wildlife Value
Sweet Potato draws honeybees (low value, Growable Ground Plant Database). Planting it near vegetable beds can lift fruit set on neighboring crops. Outdoors, sweet potato can only work that bloom inside Alaska's frost window — roughly 147 days, opening after the last 28°F freeze (Apr 16 - May 15) and closing at the first (Sep 24 - Oct 29), per NOAA Regional Climate Centers ACIS station record, 1991-2020.
Good to Know Before You Plant Sweet Potato
On Growable Ground, Sweet Potato means Ipomoea batatas — not to be confused with true yams (Dioscorea species). often sold as 'yams' in US markets, but sweet potato is botanically unrelated.
Alaska Cooperative Extension
For Alaska-specific cultivar recommendations, planting calendars, and pest pressure for sweet potato, the canonical source is UAF Cooperative Extension Service. Their fact sheets carry the local trial data we can't generalize across 50 states.
Is Sweet Potato native to Alaska?
No — the USDA PLANTS Database lists Sweet Potato as introduced rather than native in the Lower 48, so it is not part of Alaska's native flora. It grows here as a garden plant; pairing it with a few Alaska natives keeps local pollinators fed too.
Looking for plants that belong here? The Alaska growing guide lists USDA-documented natives for the state.
Native-range data: USDA PLANTS Database state-distribution records, accessed 2026-07-01.
Common Questions About Growing Sweet Potato in Alaska
When can I plant Sweet Potato in Alaska?
Alaska's last spring hard freeze (28°F) clears between Apr 16 and May 15, and the first fall hard freeze lands between Sep 24 and Oct 29 (NOAA Regional Climate Centers ACIS, 1991-2020). Sweet Potato is frost-tender — its killing temperature is 41°F (FAO ECOCROP — the point where cold damages growing tissue, not a winter-survival floor) — so wait two to three weeks past your site's last hard freeze, when light frost has also stopped, before planting out.
Can Sweet Potato mature before first frost in Alaska?
Yes — Sweet Potato matures in 110 days (Growable Ground Plant Database), and Alaska's dependable hard-freeze-free window runs 132 days (NOAA Regional Climate Centers ACIS, 1991-2020), leaving 22 days of margin. Plant once the last hard freeze has passed — two to three weeks later for anything tender — and it ripens ahead of the first fall freeze.
What hardiness zone is Sweet Potato grown in across Alaska?
Alaska spans USDA hardiness zones 1a-9a (USDA ARS PHZM 2023). Sweet Potato carries a range of zones 3-11, so the overlap zones are where outdoor growing is most reliable.
How many frost-free days does a typical Alaska site have?
A typical Alaska site sees ~147 frost-free days per year (derived from NOAA Regional Climate Centers ACIS station record, 1991-2020). Sweet Potato needs 80+ frost-free days, so check whether your local microclimate runs above or below the state average before settling on a planting date. In cooler counties like North Slope, the freeze-free season runs shorter than the state average, so verify your own county's window.
Is Sweet Potato native to Alaska?
No — the USDA PLANTS Database lists Sweet Potato as introduced rather than native in the Lower 48, so it is not part of Alaska's native flora. It grows here as a garden plant; pairing it with a few Alaska natives keeps local pollinators fed too.
How should I amend the soil for Sweet Potato in Alaska?
Sweet Potato tolerates pH 4-8.7 (FAO ECOCROP). That is a 4.7-unit span, acid ground through alkaline, so pH is rarely what limits this plant on a Alaska site — amend for drainage and organic matter first.
Will Sweet Potato actually grow on my specific land in Alaska?
State-level zone + climate data is a sketch. A Growable Ground parcel report scores sweet potato against your address's exact soil pH, drainage, sun, and frost-date data drawn from USDA SSURGO, NOAA, and PRISM — not state averages.
Check your specific parcel in Alaska
State-level data is a sketch. Your Growable Ground report scores sweet potato against your parcel's exact soil, sun, drainage, and frost data — not zone averages.
Three things about your lot that Alaska sweet potato averages can't show:
We read public map data around Alaska — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Alaska sweet potato average
Explore More
Growing guides for sweet potato
Analysis by the Growable Ground research team, grounded in USDA PLANTS, USDA NRCS SSURGO, NOAA Climate Normals (1991-2020), and named Cooperative Extension sources. How we know →
Cite this dataset
Kirchick, M. (2026). Growable Ground Plant Database [Data set]. Zenodo. https://doi.org/10.5281/zenodo.21435643
Licensed CC BY-NC 4.0. DOI 10.5281/zenodo.21435643
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