Planting Zone 3b: Plants That Grow in USDA Hardiness Zone 3b

USDA hardiness zone 3b covers areas where the coldest winter night averages −35 °F to −30 °F (−37.2 °C to −34.4 °C). 204 ZIP codes in 5 states fall in zone 3b, mostly in Minnesota, North Dakota, Montana, Maine and Wisconsin. PlantoScan lists 104 plants that survive winter outdoors in zone 3b.

Winter low (°F)
−35 °F to −30 °F
Winter low (°C)
−37.2 °C to −34.4 °C
US ZIP codes
204
Hardy plants
104

What Temperatures Define Hardiness Zone 3b?

Hardiness zone 3b is defined by an average annual extreme minimum temperature of −35 °F to −30 °F (−37.2 °C to −34.4 °C). This is the warmer half of zone 3, which spans −40 °F to −30 °F in total.

The value is a 30-year average of each winter's single coldest night, taken from 1991–2020 weather records for the 2023 USDA map. Individual winters regularly run a few degrees colder, so plants rated exactly to zone 3bbenefit from mulch and a sheltered spot. Gardeners who don't know their zone yet can look up their USDA hardiness zone by ZIP code before comparing plants.

← Colder: zone 3a (−40 °F to −35 °F)Warmer: zone 4a (−30 °F to −25 °F) →

Which States Are in Hardiness Zone 3b?

Zone 3b appears in 5 states of the contiguous US. Minnesota, North Dakota, Montana, Maine and Wisconsin have the most ZIP codes in zone 3b, based on the official 2023 USDA ZIP code table.

  • Minnesota · 123 ZIPs
  • North Dakota · 54 ZIPs
  • Montana · 25 ZIPs
  • Maine · 1 ZIPs
  • Wisconsin · 1 ZIPs

Hardiness zones follow elevation and water, not state lines, so most states span several zones.

What Plants Grow in Zone 3b?

104 plants in PlantoScan's catalogue are hardy in zone 3b, meaning zone 3b falls inside their hardiness range. They include 28 trees, 12 shrubs, 31 perennials, herbs & flowers, 7 vines & climbers.

Trees for Zone 3b (28)

Shrubs for Zone 3b (12)

Perennials, Herbs & Flowers for Zone 3b (31)

Vines & Climbers for Zone 3b (7)

Succulents & Cacti for Zone 3b (3)

Grasses for Zone 3b (6)

Ferns for Zone 3b (8)

Other Plants for Zone 3b (9)

Which Popular Plants Aren't Hardy in Zone 3b?

These popular plants need a warmer zone than 3b to survive winter outdoors. Grow them as houseplants, in containers that move indoors before the first frost, or as annuals replanted each spring.

How Do You Garden Successfully in Zone 3b?

Successful zone 3b gardens rely on perennials, shrubs and trees rated to zone 3 or colder. Plants rated right at zone 3b survive typical winters but benefit from mulch, windbreaks and a spot near a warm wall.

A hardiness zone describes winter cold only. Planting dates follow your local last spring frost and first fall frost, which differ by weeks within zone 3b — a last frost date calculator by ZIP code gives the dates for your garden. Summer heat, rainfall and soil drainage decide whether a hardy plant thrives. Microclimates matter as well: raised beds, slopes and paved areas warm up faster, while low ground collects cold air on still nights.

Zone temperatures and ZIP codes: 2023 USDA Plant Hardiness Zone Map, USDA Agricultural Research Service and the PRISM Climate Group, Oregon State University. Plant hardiness ranges come from PlantoScan's plant database and are estimates — local conditions, cultivars and winter protection change what survives.