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Zone 3b: What Grows and How to Garden There

Zone 3b grows a wide range of hardy fruit, including zone 3 apples on standard rootstock, hardy pears, plums, bush cherries and haskaps, along with lilacs, rugosa roses, peonies, daylilies, hostas and spring bulbs. Plants rated zone 4 are risky, and the short season calls for early vegetable varieties and warmed soil.

Coldest winter night
-35 to -30°F
ZIP codes in the zone
222
Typical last frost
May 17
Typical first frost
September 24
Frost-free season
About 129 days

Frost dates in zone 3b

Hardiness zones measure winter cold, so places in one zone can have quite different springs. Across zone 3b, the typical last frost ranges from about May 12 to May 29, and the first fall frost from September 13 to October 1 (the earliest and latest tenth of ZIP codes). For a typical place in the zone:

  • May 4Risky: a later frost happens in 9 years out of 10
  • May 17Typical last frost
  • May 30Safe: a later frost only 1 year in 10

What a zone 3b winter means

Zone 3b is the colder edge of the northern plains and north woods. Most perennials sold in the region are rated to zone 3 or 4, so read tags: zone 3 plants are dependable, zone 4 plants need shelter and snow cover. NDSU Extension’s advice for growing anything outside your zone is to be ready to protect it, and to accept that one especially cold winter may be its last. The University of Vermont adds that lower zones usually mean a shorter season too, because the ground takes longer to warm in spring.

Where zone 3b is

Zone 3b runs along the northern tier: northern Minnesota around International Falls and Roseau, parts of North Dakota and northern Montana, the far north of Maine, and parts of Orleans and Essex counties in Vermont’s Northeast Kingdom. In Alaska it includes parts of the Fairbanks area and other interior communities.

Fruit trees and small fruit

  • Apples: zone 3 apples on standard, hardy rootstock. NDSU says dwarfing rootstocks are not hardy in zone 3. The Carrington station recommends ‘Hazen’, ‘Honeycrisp’ and ‘Zestar’ in North Dakota, though NDSU calls the last two marginal in zone 3; ‘Haralson’ is the standard cooking apple of the Upper Midwest.
  • Pears: ‘Golden Spice’, ‘Summercrisp’ and ‘Ure’.
  • Plums: ‘Pembina’, ‘Pipestone’, ‘Toka’ and ‘Waneta’ at Carrington; SDSU rates ‘Underwood’, ‘Black Ice’ and ‘LaCrescent’ very hardy.
  • Cherries: Saskatchewan bush cherries (‘Carmine Jewel’, ‘Romeo’, ‘Juliet’), hardy to zone 3 in Montana trials, and the tree-type ‘Evans’.
  • Grapes: NDSU calls ‘Valiant’ the easiest, hardiest grape for North Dakota.
  • Berries: haskaps (‘Indigo Gem’, ‘Tundra’, ‘Borealis’ with pollinizers), juneberries, and currants such as ‘Red Lake’.

Perennials, bulbs and shrubs

Lilacs and rugosa roses are hardy to zone 2. Peonies, daylilies, hostas, Siberian iris and daffodils are long-lived. Delphinium, lupine and hybrid tulips are shorter-lived and may need replanting.

Short-season vegetables

Wyoming Extension notes that where the season is under about 100 days, sweet corn, tomatoes, peppers, squash and melons often fail without help. Choose early varieties bred in the northern US or Canada, use transplants, and lay clear plastic early in spring, which can warm soil 10-15°F in a few days.

What to plant each month in zone 3b

For a typical place in the zone. Your own dates may be a couple of weeks earlier or later; enter your ZIP code to see them.

  1. January

    Start indoors: onions

  2. February

    Start indoors: collard greens, leeks, onions, petunias, ranunculus

  3. March

    Start indoors: black-eyed susans, broccoli, cabbages, cauliflower, chives, collard greens, ginger, kale, leeks, lettuce, marigolds, onions, oregano, parsley, peppers, petunias, ranunculus, rosemary, sage, snapdragons

  4. April

    Start indoors: basil, black-eyed susans, cabbages, celery, chives, cilantro, collard greens, eggplants, ginger, lettuce, marigolds, nasturtiums, peppers, ranunculus, sage, snapdragons, spinach, swiss chard, tomatoes, zinnias

    Plant or sow outdoors: beets, black-eyed susans, blackberries, blueberries, broccoli, cabbages, carrots, cauliflower, chives, cilantro, collard greens, figs, garlic, gladioli, grapes, grass seed, hollyhocks, kale, leeks, lettuce, onions, parsley, peas, poppies, radishes, ranunculus, raspberries, rhubarb, roses, spinach, strawberries, swiss chard, turnips, wildflowers

  5. May

    Start indoors: basil, cantaloupes, cosmos, cucumbers, okra, pumpkins, ranunculus, watermelons, winter squash, zucchini

    Plant or sow outdoors: asparagus, beets, black-eyed susans, blackberries, broccoli, cabbages, carrots, cauliflower, chives, cilantro, dahlias, dill, figs, garden mums, ginger, gladioli, grapes, green onions, kentucky bluegrass, lavenders, leeks, lettuce, lilies, marigolds, mints, nasturtiums, onions, oregano, parsley, perennial ryegrass, petunias, potatoes, radishes, ranunculus, rosemary, roses, sage, snapdragons, spinach, sunflowers, sweet corn, sweet peas, swiss chard, tall fescue, thyme, turnips, zinnias

  6. June

    Start indoors: cosmos, okra

    Plant or sow outdoors: asparagus, basil, bermudagrass, cantaloupes, celery, centipedegrass, cosmos, cucumbers, eggplants, garden mums, ginger, green beans, green onions, kentucky bluegrass, okra, peanuts, peppers, perennial ryegrass, pumpkins, st. augustinegrass, sunflowers, sweet peas, sweet potatoes, tall fescue, tomatoes, watermelons, winter squash, zoysiagrass, zucchini

    Plant for fall: brussels sprouts, collard greens, lettuce, swiss chard

  7. July

    Plant or sow outdoors: bermudagrass, celery, centipedegrass, cosmos, green onions, okra, peanuts, st. augustinegrass, sweet potatoes, zoysiagrass

    Plant for fall: azaleas, bearded irises, beets, broccoli, cabbages, carrots, cauliflower, clematis, collard greens, coneflowers, daylilies, hostas, hydrangeas, kale, lettuce, peas, radishes, roses, saffron, snapdragons, spinach, swiss chard, turnips

  8. August

    Plant or sow outdoors: bermudagrass, centipedegrass, zoysiagrass

    Plant for fall: azaleas, bearded irises, beets, broccoli, cabbages, cauliflower, clematis, coneflowers, crocuses, daffodils, daylilies, grass seed, hostas, hyacinths, hydrangeas, kale, lilies, ornamental alliums, peonies, radishes, roses, saffron, spinach, tulips, turnips

  9. September

    Plant for fall: crocuses, daffodils, daylilies, garlic, hyacinths, lilies, ornamental alliums, peonies, tulips

  10. October

    Plant for fall: crocuses, garlic, hyacinths, ornamental alliums, tulips

Planting schedules for zone 3b

Where zone 3b is

States with zone 3b ZIP codes, the largest first: Minnesota, North Dakota, Alaska, Montana, Maine.

Zone 3aZone 4aAll zones and the zone finder

Questions

Which pear trees are hardy in zone 3b?

NDSU's Carrington station reports many confirmations of hardiness in North Dakota for 'Golden Spice', 'Summercrisp' and 'Ure', and success with 'Nova' and 'Patten'. 'Gem', 'Gourmet', 'Parker' and 'Harrow Delight' are probably not hardy in zone 3.

Do tulips and daffodils survive zone 3b winters?

Yes. Plant them in fall, tulips and daffodils 6-8 inches deep and crocus and grape hyacinths 3-4 inches deep (Iowa State). A layer of mulch after planting helps prevent freeze-thaw heaving. Daffodils return for decades; hybrid tulips often fade within a few years.

Should I mulch perennials for winter in zone 3b?

Snow is the best mulch. Where snow is unreliable, Wisconsin Extension suggests leaving perennials unpruned and mulching crowns 6-8 inches deep with straw or evergreen boughs around Thanksgiving or before the first snow. The goal is to stop freeze-thaw cycles, not to keep the ground from freezing.