Alaska planting calendar

When to plant sweet potatoes in Alaska — sow, transplant & harvest dates

Alaska is mostly USDA zone 4b (range 1a-8b). Dates below are derived from sweet potatoes's frost tolerance and Alaska's frost window — not generic national averages.

Sweet potatoes planting timetable for Alaska

Stage	When in Alaska	Anchor
Start seeds indoors	mid-April (April 13)	6 weeks before the last frost (late May)
Transplant outside	mid-June (June 15)	21 days after the last frost (late May)
First harvest (estimate)	late September (September 28)	~105 days from transplant

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why Alaska's climate shifts the sweet potatoes dates

Alaska's last spring frost averages late May and first fall frost mid-September, which sets the whole planting clock. Alaska spans the widest zone range of any state, from sub-arctic interior to mild maritime southeast. Season length and summer light, not just cold, shape what grows. Wait for warm soil — sweet potatoes stall in cold ground even after the air warms, so don't rush them out.

Sweet potatoes are extremely frost-tender and demand warm soil — do not transplant slips until soil temperature at 4-inch depth holds at 18 °C (65 °F) or above, typically 3 weeks after the last spring frost. Short-season zones (z5-6) should start slips indoors under lights 5-6 weeks early to ensure 100-120 frost-free days. Avoid zones 3-4 without a floating row cover season-extension strategy; in z9-11 slips can go out as early as late March.

Frost-risk note

Don't plant before late May — even a light frost will kill seedlings overnight. In the interior near Fairbanks (zone 1a-2b) the safe date runs a week or two later.

Regional variation within Alaska

the interior near Fairbanks (zone 1a-2b) runs roughly 1-2 weeks behind the state average; the southeast coast and panhandle around Sitka (zone 8b) can plant 1-2 weeks earlier.

Anchorage — USDA zone 5a
Fairbanks — USDA zone 2a
Juneau — USDA zone 7a
Sitka — USDA zone 8a

What else to plant in Alaska around then

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Quick-grow guide

Sun: Full sun — 6-8 hours direct.
Soil temperature for germination: Soil 18-24 °C (65-75 °F) for slip rooting.
Spacing: 12-18 inches (30-45 cm) between plants.
Days to harvest: ~105 days from planting out.

Frequently asked questions

When is the best time to plant sweet potatoes in Alaska?

In Alaska (mostly USDA zone 4b), sow sweet potatoes indoors around mid-April, transplant outdoors mid-June (after the last frost, late May), and harvest from late September. Sweet potatoes are frost-tender — a single light frost kills seedlings, so they only go outside once frost danger has fully passed and the soil is warm.

What USDA zone is Alaska?

Most of Alaska sits in USDA hardiness zone 4b, with the state spanning roughly 1a-8b from the interior near Fairbanks (zone 1a-2b) to the southeast coast and panhandle around Sitka (zone 8b). The last spring frost averages late May and the first fall frost mid-September.

Can you grow sweet potatoes in Alaska?

Yes. Alaska's dominant zone 4b supports sweet potatoes — the key is timing. Sweet potatoes are frost-tender — a single light frost kills seedlings, so they only go outside once frost danger has fully passed and the soil is warm.

Does the planting date change across Alaska?

the interior near Fairbanks (zone 1a-2b) runs roughly 1-2 weeks behind the state average; the southeast coast and panhandle around Sitka (zone 8b) can plant 1-2 weeks earlier.

What else can I plant in Alaska around the same time?

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.