Planting Zone 6a: Plants That Grow in USDA Hardiness Zone 6a

USDA hardiness zone 6a covers areas where the coldest winter night averages −10 °F to −5 °F (−23.3 °C to −20.6 °C). 5,183 ZIP codes in 29 states fall in zone 6a, mostly in Illinois, Michigan, Indiana, Ohio and Pennsylvania. PlantoScan lists 220 plants that survive winter outdoors in zone 6a.

Winter low (°F)
−10 °F to −5 °F
Winter low (°C)
−23.3 °C to −20.6 °C
US ZIP codes
5,183
Hardy plants
220

What Temperatures Define Hardiness Zone 6a?

Hardiness zone 6a is defined by an average annual extreme minimum temperature of −10 °F to −5 °F (−23.3 °C to −20.6 °C). This is the colder half of zone 6, which spans −10 °F to 0 °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 6abenefit 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 5b (−15 °F to −10 °F)Warmer: zone 6b (−5 °F to 0 °F) →

Which States Are in Hardiness Zone 6a?

Zone 6a appears in 29 states of the contiguous US. Illinois, Michigan, Indiana, Ohio and Pennsylvania have the most ZIP codes in zone 6a, based on the official 2023 USDA ZIP code table.

  • Illinois · 646 ZIPs
  • Michigan · 640 ZIPs
  • Indiana · 567 ZIPs
  • Ohio · 544 ZIPs
  • Pennsylvania · 510 ZIPs
  • New York · 499 ZIPs
  • Colorado · 274 ZIPs
  • Missouri · 216 ZIPs
  • Nebraska · 206 ZIPs
  • Kansas · 178 ZIPs
  • Massachusetts · 154 ZIPs
  • New Hampshire · 119 ZIPs
  • Maine · 109 ZIPs
  • Utah · 108 ZIPs
  • New Mexico · 64 ZIPs
  • West Virginia · 57 ZIPs
  • Idaho · 52 ZIPs
  • Connecticut · 51 ZIPs
  • Wisconsin · 47 ZIPs
  • Montana · 30 ZIPs
  • Iowa · 29 ZIPs
  • Oregon · 27 ZIPs
  • Washington · 17 ZIPs
  • Nevada · 11 ZIPs
  • Maryland · 9 ZIPs
  • California · 7 ZIPs
  • Arizona · 6 ZIPs
  • Virginia · 4 ZIPs
  • Vermont · 2 ZIPs

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

What Plants Grow in Zone 6a?

220 plants in PlantoScan's catalogue are hardy in zone 6a, meaning zone 6a falls inside their hardiness range. They include 81 trees, 32 shrubs, 49 perennials, herbs & flowers, 14 vines & climbers.

Trees for Zone 6a (81)

Shrubs for Zone 6a (32)

Perennials, Herbs & Flowers for Zone 6a (49)

Vines & Climbers for Zone 6a (14)

Succulents & Cacti for Zone 6a (4)

Grasses for Zone 6a (17)

Ferns for Zone 6a (10)

Other Plants for Zone 6a (13)

Which Popular Plants Aren't Hardy in Zone 6a?

These popular plants need a warmer zone than 6a 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 6a?

Successful zone 6a gardens rely on perennials, shrubs and trees rated to zone 6 or colder. Plants rated right at zone 6a 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 6a — 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.