What Planting Zones Are in Maine?
Maine spans USDA hardiness zones 3b to 7a, where the average coldest winter night ranges from −35 °F to 5 °F (−37.2 °C to −15 °C). Zone 5a covers the most ZIP codes, 32%, and zones 5a to 6a together cover 86% of the state.
- Zone 3b<1% · 1 ZIP
- Zone 4a5% · 26 ZIPs
- Zone 4b6% · 30 ZIPs
- Zone 5a32% · 151 ZIPs
- Zone 5b31% · 150 ZIPs
- Zone 6a23% · 109 ZIPs
- Zone 6b2% · 10 ZIPs
- Zone 7a<1% · 1 ZIP
Bars show each zone's share of the 478 Maine ZIP codes in the official 2023 USDA ZIP code table; select a zone for its temperatures and hardy plants.
What Hardiness Zone Are Maine Cities In?
Portland is in zone 6a, Lewiston is in zone 5b, Bangor is in zone 5a and South Portland is in zone 6a. The table lists the zone, winter low and average frost dates for 17 Maine cities, using the ZIP code nearest each city center.
| City | ZIP | Zone | Winter low | Last frost | First frost |
|---|---|---|---|---|---|
| Portland | 04108 | 6a | −10 °F to −5 °F | Apr 26 | Oct 15 |
| Lewiston | 04240 | 5b | −15 °F to −10 °F | Apr 25 | Oct 19 |
| Bangor | 04401 | 5a | −20 °F to −15 °F | May 4 | Oct 4 |
| South Portland | 04106 | 6a | −10 °F to −5 °F | Apr 26 | Oct 15 |
| Auburn | 04210 | 5b | −15 °F to −10 °F | Apr 25 | Oct 19 |
| Sanford | 04073 | 5b | −15 °F to −10 °F | May 16 | Sep 30 |
| Biddeford | 04046 | 6a | −10 °F to −5 °F | May 9 | Oct 3 |
| Westbrook | 04092 | 5b | −15 °F to −10 °F | Apr 26 | Oct 15 |
| Saco | 04064 | 6a | −10 °F to −5 °F | Apr 26 | Oct 15 |
| Augusta | 04330 | 5b | −15 °F to −10 °F | Apr 27 | Oct 16 |
| Ellsworth | 04684 | 5b | −15 °F to −10 °F | May 8 | Oct 9 |
| Bath | 04530 | 6a | −10 °F to −5 °F | May 10 | Oct 6 |
| Presque Isle | 04769 | 4a | −30 °F to −25 °F | May 14 | Sep 26 |
| Rockland | 04841 | 6a | −10 °F to −5 °F | Apr 27 | Oct 19 |
| Belfast | 04915 | 5b | −15 °F to −10 °F | May 7 | Oct 5 |
| Calais | 04619 | 5b | −15 °F to −10 °F | May 5 | Oct 13 |
| Eastport | 04631 | 6a | −10 °F to −5 °F | Apr 29 | Oct 25 |
Zone: 2023 USDA ZIP code table for the ZIP code nearest each city's Census center point. Frost dates: 50% (median) dates from the nearest NOAA station, 1991–2020 normals. Cities: the largest Maine places by 2024 Census population estimates, spread across the state, plus the largest place in each common zone. Large cities can span two half zones.
Which Parts of Maine Are in Each Zone?
Zone 4a, the coldest Maine zone with towns, covers 5% of ZIP codes around Presque Isle and Caribou. Zone 6a, the warmest with towns, covers 23% around Portland, South Portland and Biddeford. The table lists the largest places in every zone.
| Zone | Avg. coldest night | Share of ZIPs | Largest places in this zone |
|---|---|---|---|
| Zone 3b | −35 °F to −30 °F | <1% (1) | Rural ZIP codes only |
| Zone 4a | −30 °F to −25 °F | 5% (26) | Presque Isle, Caribou |
| Zone 4b | −25 °F to −20 °F | 6% (30) | Rural ZIP codes only |
| Zone 5a | −20 °F to −15 °F | 32% (151) | Bangor, Brewer, Old Town |
| Zone 5b | −15 °F to −10 °F | 31% (150) | Lewiston, Auburn, Sanford, Westbrook |
| Zone 6a | −10 °F to −5 °F | 23% (109) | Portland, South Portland, Biddeford, Saco |
| Zone 6b | −5 °F to 0 °F | 2% (10) | Rural ZIP codes only |
| Zone 7a | 0 °F to 5 °F | <1% (1) | Rural ZIP codes only |
Places: incorporated places with 1,000+ residents, assigned the zone of the ZIP code nearest their Census center point.
What Do the Hardiness Zones Mean for Maine Gardeners?
A Maine gardener in zone 7a sees winter lows about 35 °F milder than one in zone 3b, so a shrub or perennial that thrives in one part of the state can die in another. Choose plants rated to your own ZIP code's zone or colder.
Hardiness zones follow latitude, elevation and large bodies of water rather than state lines. Higher ground and inland valleys that trap cold air usually sit in colder half zones, while cities, coasts and large lakes moderate winter lows. Within Maine, a plant labelled “zones 5–6” survives winter in at least 86% of ZIP codes, but plants at the edge of their range benefit from mulch and a sheltered spot. Enter a ZIP code in the USDA hardiness zone finder by ZIP code to check your exact half zone before buying perennials.
A zone describes winter cold only. Summer heat, humidity, rainfall and soil decide whether a cold-hardy plant thrives, and planting dates for vegetables follow frost dates, not zones: two Maine towns in the same zone can have last frosts weeks apart.
What Plants Grow Well Across Maine?
199 plants in PlantoScan's catalogue are hardy in every zone from 5a to 6a, the zones that cover 86% of Maine ZIP codes. Popular examples include hydrangea, peony and daisy.
Hydrangea
Hydrangea macrophylla
Zone 5 – 9
AI generated
Peony
Paeonia lactiflora
Zone 3 – 8
AI generated
- DaisyBellis perennisPlantoScan
Daisy
Bellis perennis
Zone 4a – 8b
Chrysanthemum
Chrysanthemum morifolium
Zone 5a – 9b
PlantoscanAI generated
Poppy
Papaver somniferum
Zone 3a – 9b
AI generated
Carnation
Dianthus caryophyllus
Zone 5a – 9b
AI generated
Daffodil
Narcissus poeticus
Zone 3 – 8
AI generated
Arugula
Eruca sativa
Zone 5a – 10b
AI generated
Alfalfa
Medicago sativa
Zone 3a – 10a
AI generated
Hardiness ranges come from PlantoScan's plant database; gardeners in Maine's colder or warmer edge zones should check each plant's full range.
When Is the Last Frost in Maine?
Across most Maine ZIP codes, the average last spring frost falls between April 27 and May 16, from April 25 in Lewiston to May 16 in Sanford. Tender vegetables such as tomatoes go out 1 to 2 weeks after the local date.
The last and first frost dates for Maine cities include the safer 90% planting date, the fall frost date, growing season length and a tomato planting table for each city.
Frequently Asked Questions
- What planting zone is Maine?
- Maine spans USDA hardiness zones 3b to 7a on the 2023 USDA Plant Hardiness Zone Map. Zone 5a is the most common, covering 32% of the state's 478 ZIP codes, and zones 5a to 6a together cover 86%.
- What hardiness zone is Portland, Maine?
- Portland is in USDA hardiness zone 6a (ZIP 04108), where the average coldest winter night reaches −10 °F to −5 °F. Its average last spring frost is April 26 and its first fall frost October 15.
- What hardiness zone is Lewiston, Maine?
- Lewiston is in USDA hardiness zone 5b (ZIP 04240), where the average coldest winter night reaches −15 °F to −10 °F. Its average last spring frost is April 25 and its first fall frost October 19.
- What hardiness zone is Bangor, Maine?
- Bangor is in USDA hardiness zone 5a (ZIP 04401), where the average coldest winter night reaches −20 °F to −15 °F. Its average last spring frost is May 4 and its first fall frost October 4.
- What is the coldest hardiness zone in Maine?
- Zone 3b (−35 °F to −30 °F) is the coldest zone in Maine, found in 1 ZIP code. The warmest is zone 7a (0 °F to 5 °F).
Zones: 2023 USDA Plant Hardiness Zone Map ZIP code table, USDA Agricultural Research Service and the PRISM Climate Group, Oregon State University, used without changes. Frost dates: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals. City locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. PlantoScan is not affiliated with or endorsed by these agencies.