USDA Zone 1b
Zone 1 · The Far North
Average annual extreme minimum temperature: -55 to -50 °F (-48.3°C to -45.6°C).
America's coldest gardens — interior and northern Alaska, where winters average −60 to −50°F and the entire growing year fits between early June and late August. Gardening here is real, but it is a transplants-and-season-extension craft.
By the numbers
- Median last frost
- May 29
- Median first frost
- August 28
- Median season
- 91 days
- ZIPs tracked
- 11
Medians across every ZIP we track in zone 1b, derived from NOAA 1991–2020 climate normals. Look up your own ZIP for local dates — within a zone, frost varies by weeks.
Where you'll find zone 1
Zone 1 exists only in Alaska — the northern and central interior. No part of the contiguous 48 states is this cold; the lower 48's coldest pocket (north-central Minnesota) bottoms out at zone 2b.
Vegetables that earn their keep
- Peas — "one of Alaska's most satisfactory vegetables" (UAF)
- Cabbage and the cabbage family
- Carrots, beets, turnips, rutabagas, radishes
- Broccoli and Brussels sprouts
- Kale and kohlrabi
- Lettuce and mustard greens
- Beans (quick varieties)
Fruits & perennials that overwinter
- Apples on cold-hardy crab rootstock: Rescue, Heyer #12, Patterson, Kerr, Norland (UAF, zones 1–2)
- Honeyberry / haskap (Lonicera caerulea) — hardy in zones 1–8
Cool crops, cold soils
The cabbage family and root crops are the backbone of the far-north garden — UAF's blunt assessment is that many popular vegetable varieties simply don't perform in Alaska's cold soils. Tomatoes, corn, and cucumbers are marginal without special protection. Choose varieties bred or proven for the north, and start nearly everything indoors: tomatoes about 8 weeks before set-out, cabbage about 6.
The midnight sun cuts both ways
Alaska's long summer days drive fast growth, but they also push long-day-sensitive crops to bolt — peas bloom early and beets often run to seed before the root fills out (UAF). And the hardiness zone won't warn you about mid-season frost: UAF documented a valley garden that froze on three June nights and two July nights in a year when a nearby upland site never froze at all. Know your site, not just your zone.
Season extension is the whole game
UAF's measurements put clear plastic mulch up to 30°F warmer at the soil surface than bare ground on sunny days — enough to make corn or tomatoes possible in a warm year. Raised beds and mounds 10–12 inches high warm faster and drain better. Between transplants, plastic, and raised soil, the working season stretches well past what the calendar suggests.
Trees are a long bet
Fruit trees here need cold-hardy crab rootstocks — the standard dwarfing rootstocks sold in the lower 48 are not reliably winter-hardy in Alaska (UAF). Young trunks need insulation or shade against winter sunscald for at least their first three winters, and UAF rates moose protection "may be the most important action you take."
Plant guides, timed to your frost dates
Every guide gives its planting calendar relative to your last frost — the dates above (or your ZIP's) drop straight in.