Zone 1a covers 5 ZIP codes in Alaska on the 2023 map. Cities in it include Circle, Allakaket and Stevens Village in Alaska.

USDA hardiness zone 1a, -60°F to -55°F

Planting Zone 1a: Where It Is and What Grows

Q: What does zone 1a mean?

Zone 1a means the coldest night of the winter averages -60°F to -55°F, measured over 1991 to 2020. It is an average of each winter's lowest temperature, so some winters go colder.

Q: What can I plant in zone 1a?

None of the plants listed here are rated for zone 1a. The hardiest of them are rated down to zone 2a: arrowwood viburnum, red twig dogwood, red maple, paper birch, Colorado blue spruce and asparagus. Gardens this cold lean on annual vegetables grown in the short summer.

Q: What is the difference between zone 1a and 1b?

Five degrees. Zone 1a averages -60°F to -55°F and 1b averages -55°F to -50°F, so 1a is the colder half. A plant rated for zone 1 suits both.

Q: Will a plant rated for zone 1b survive in zone 1a?

Not reliably. A plant rated down to 1b is rated for winter lows of -55°F to -50°F, and a typical zone 1a winter reaches -60°F to -55°F. Choose plants whose range on the tag includes 1a.

The coldest night of the winter averages -60°F to -55°F in zone 1a. Where it is on the 2023 USDA map, the towns in it and the zones either side.

5 ZIP codes

Where zone 1a is

Zone 1a covers 5 ZIP codes in Alaska: Alaska (5).

Cities and towns in zone 1a

Tap a town for its own frost dates and this month’s jobs; a hill or a valley a few miles off can be half a zone either side.

Either side

The zones next to 1a

Each half zone is five degrees. Zone 1b is five degrees warmer at -55°F to -50°F.

Zone 1b, warmer-55°F to -50°F

Questions

Zone 1a questions

What does zone 1a mean?

Where is zone 1a?

What can I plant in zone 1a?

What is the difference between zone 1a and 1b?

Will a plant rated for zone 1b survive in zone 1a?

Your own dates, by ZIP

Find your zone by ZIPYour zone, your frost dates and this month’s jobs for your address.Seed starting calendarWhen to start each vegetable indoors, by ZIP.Frost dates by ZIPYour last spring and first fall frost, with the odds either side.First frost forecastWhen the first fall frost usually arrives, state by state.Soil temperatureWhen the ground is warm enough to sow.When to plant garlicThe fall planting window by ZIP.

Sources. USDA Plant Hardiness Zone Map, ZIP code tables (2023 and 2012), PRISM Climate Group, Oregon State University; USDA Plant Hardiness Zone Map; USDA Unveils Updated Plant Hardiness Zone Map (USDA Agricultural Research Service, November 15, 2023); NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal, by station (v1.0.1); NC State Extension Gardener Plant Toolbox. Zone frost dates are the medians of the NOAA 1991 to 2020 station normals inside the zone.