Gardening in Alaska

Hardiness zones in Alaska

A USDA hardiness zone tells you the average annual minimum winter temperature for a location, nothing more. It does not describe summer heat, rainfall, humidity, or the kind of soil in your yard. Alaska spans zones 1a through 8b, based on readings from 112 weather stations across the state. That is the widest zone range covered on this site. A frost-hardy shrub that thrives in Juneau can die outright in Fairbanks or Barrow. Find your own zone first, then check a plant's listed range against it before you buy or plant anything. A plant rated for zone 6 will likely struggle or fail outdoors in a zone 2 yard. This holds true even if it grows well a few hundred miles to the south. Use the frost dates below alongside your zone, since they tell you when to plant and when to bring tender plants in.

• Zone 1a
• Zone 1b
• Zone 2a
• Zone 2b
• Zone 3a
• Zone 3b
• Zone 4a
• Zone 4b
• Zone 5a
• Zone 5b
• Zone 6a
• Zone 6b
• Zone 7a
• Zone 7b
• Zone 8a
• Zone 8b

Frost dates

Your last frost date marks the point in spring when the risk of a freeze drops low enough to plant tender crops outdoors. Across Alaska's weather stations, the average last spring frost can come as early as April 11 in the mildest spots. In the coldest spots, it can hold off until as late as June 12. That six-week spread means a gardener on the southern coast can be planting tomatoes while one farther north is still watching for snow. The first fall frost works the same way in reverse, closing out the growing season. It arrives as early as August 21 in some parts of the state and as late as November 5 in others. Wherever you garden, treat these dates as averages, not guarantees, since a frost can still strike earlier or later than normal. Check a local source for your own station if one is close by. Plan a buffer of a week or two around both dates, just to be safe. Hold off on tender seedlings until after your last frost date. Bring in or cover sensitive plants as the first fall frost date in your area gets close.

Climate

Alaska's climate varies more than any other state covered on this site, from the near-arctic north to the maritime southeast coast. The hardiness zones recorded here stretch from 1a, the coldest, to 8b, the mildest, a range pulled from 112 weather stations spread across the state. No single statewide climate exists; a gardener in one zone faces a completely different growing year than a gardener three zones away. The length of the frost-free growing season reflects that same spread. Some stations report as few as 26 frost-free days a year, while others report as many as 202. A season of 26 days limits you to only the fastest, hardiest crops started indoors and moved out late. A season of 202 days opens the door to a far wider range of vegetables, flowers, and even some fruiting shrubs. The state's weather stations sit far apart, across very different terrain. So the zone and frost figures here are averages for each station, not one forecast for the whole state. Use the zone and frost data for the station closest to you rather than treating any single number as true for the whole state. Elevation, distance from the coast, and latitude all push your local conditions away from the statewide range in ways these figures alone cannot capture.

Season length

The frost-free growing season is the stretch of days between your last spring frost and your first fall frost. It is the window for anything that can't handle a freeze. Across Alaska, that window swings wildly depending on where you garden. On the short end, a weather station records as few as 26 frost-free days a year. On the long end, another logs as many as 202. That gap of more than six months separates two very different gardens. One needs cold-hardy, fast-maturing plants, and the other can grow almost anything suited to its zone. Count the frost-free days for your own station before choosing what to plant, rather than assuming a statewide average applies to your yard.