Zone 1b: Gardening in Interior and Arctic Alaska
Zone 1b covers a few remote communities in interior and northwest Alaska where winter lows are among the coldest in the country. Few perennials are rated this cold, so permanent plantings are limited to the toughest zone 2 shrubs and berries under deep snow, while summer vegetable gardens succeed with Alaska-tested varieties and warmed soil.
- Coldest winter night
- -55 to -50°F
- ZIP codes in the zone
- 11
Frost in zone 1b
Frost decides the growing season here. Only 3 of zone 1b's 11 ZIP codes have a nearby weather station with frost records, too few for a zone-wide frost date; where it is measured, the frost-free season is about 94 days. Valley gardens can freeze in June or July. Enter your ZIP code to see the frost dates of your nearest station.
What a zone 1b winter means
Zone 1b is only one half zone milder than the coldest category on the map, and the same rule holds: almost nothing sold as a perennial has been tested this cold. Hardiness ratings stop at zone 2 for nearly all shrubs and fruit, so every permanent planting is an experiment, and snow cover makes the difference between a plant that comes back and one that does not. NDSU Extension notes that snow insulates the soil and limits frost depth, and recommends shoveling extra snow over exposed plants.
Where zone 1b is
The zone’s ZIP codes are scattered across interior and northwest Alaska, in river communities of the Yukon, Koyukuk and Tanana drainages and on the south side of the Brooks Range, such as Bettles, Galena, Tanana and Arctic Village.
Perennials, fruit and shrubs
UAF’s recommended list for the Interior and NDSU’s tree selector point to these as the hardiest choices:
- Fruit rated to zone 2a: ‘Schafer’ apple, the Romance series bush cherries (‘Crimson Passion’, ‘Carmine Jewel’, ‘Romeo’, ‘Juliet’, ‘Valentine’), ‘Early Gold’ pear and red gooseberry. Apples in Alaska are grafted onto very hardy crabapple rootstock (UAF).
- Haskaps (honeyberries): cold-hardy, early-blooming shrubs whose flowers tolerate frost. UAF says at least two compatible varieties that bloom together are needed for fruit.
- Shrubs: common lilac and rugosa rose, both hardy to zone 2 (NDSU).
Low bush forms are easier to keep under the snow. UAF notes that some fruit trees do fine while buried but suffer once they grow above the snow line.
Vegetables
Long days and cool temperatures make for sweet, fast-growing vegetables once the soil warms, according to UAF. Grow varieties from UAF’s Interior list, such as ‘Provider’ and ‘Contender’ snap beans, ‘Cylindra’ beet for its bolting resistance and ‘Waltham 29’ broccoli. Warm the soil with clear plastic, raised mounds 10-12 inches high and rows running north-south, and use row covers for extra heat early in the season.
Where zone 1b is
States with zone 1b ZIP codes, the largest first: Alaska.
Zone 1aZone 2aAll zones and the zone finder
Questions
Which fruit can I try in zone 1b?
Start with the hardiest bush fruit UAF recommends for the Interior, such as red gooseberry and 'Schafer' apple (both rated to zone 2a), the Romance series of bush cherries, and haskaps (honeyberries), which need two compatible varieties to set fruit. Plant where snow collects deepest.
How much does plastic mulch help in zone 1b?
A lot. UAF Extension says clear plastic mulch is needed all season for warm-soil crops such as squash in much of Alaska; on sunny days soil under clear plastic has measured up to 30°F warmer than unmulched soil. Free seedlings as soon as they emerge, or they will sunburn under the film.
Do hardiness zones tell me everything about my garden's climate?
No. A zone only reflects the average coldest night of winter. UAF Extension advises also tracking summer frosts, slope direction, hours of direct sun and day length, because a valley garden can freeze in June or July when nearby higher ground does not.