What Planting Zones Are in Connecticut?
Connecticut spans USDA hardiness zones 6a to 7b, where the average coldest winter night ranges from −10 °F to 10 °F (−23.3 °C to −12.2 °C). Zone 6b covers the most ZIP codes, 60%, and zones 6a to 7a together cover 99% of the state.
Bars show each zone's share of the 419 Connecticut ZIP codes in the official 2023 USDA ZIP code table; select a zone for its temperatures and hardy plants.
What Hardiness Zone Are Connecticut Cities In?
Bridgeport is in zone 7a, Stamford is in zone 7a, New Haven is in zone 7a and Hartford is in zone 6b. The table lists the zone, winter low and average frost dates for 15 Connecticut cities, using the ZIP code nearest each city center.
| City | ZIP | Zone | Winter low | Last frost | First frost |
|---|---|---|---|---|---|
| Bridgeport | 06608 | 7a | 0 °F to 5 °F | Apr 5 | Nov 6 |
| Stamford | 06905 | 7a | 0 °F to 5 °F | Apr 17 | Oct 23 |
| New Haven | 06510 | 7a | 0 °F to 5 °F | Apr 17 | Oct 27 |
| Hartford | 06103 | 6b | −5 °F to 0 °F | Apr 17 | Oct 26 |
| Waterbury | 06702 | 6b | −5 °F to 0 °F | Apr 26 | Oct 16 |
| Norwalk | 06854 | 7a | 0 °F to 5 °F | Apr 17 | Oct 23 |
| Danbury | 06811 | 6b | −5 °F to 0 °F | Apr 20 | Oct 20 |
| New Britain | 06053 | 6b | −5 °F to 0 °F | Apr 17 | Oct 26 |
| Bristol | 06010 | 6b | −5 °F to 0 °F | Apr 25 | Oct 18 |
| Meriden | 06450 | 6b | −5 °F to 0 °F | Apr 26 | Oct 16 |
| Norwich | 06360 | 6b | −5 °F to 0 °F | Apr 14 | Oct 24 |
| Danielson | 06239 | 6b | −5 °F to 0 °F | Apr 25 | Oct 19 |
| Stonington | 06379 | 7a | 0 °F to 5 °F | Apr 11 | Oct 31 |
| Bantam | 06750 | 6a | −10 °F to −5 °F | May 8 | Oct 5 |
| Fenwick | 06475 | 7a | 0 °F to 5 °F | Apr 6 | Nov 17 |
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 Connecticut 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 Connecticut Are in Each Zone?
Zone 6a, the coldest Connecticut zone, covers 12% of ZIP codes around Torrington and Litchfield. Zone 7a, the warmest with towns, covers 27% around Bridgeport, Stamford and New Haven. The table lists the largest places in every zone.
| Zone | Avg. coldest night | Share of ZIPs | Largest places in this zone |
|---|---|---|---|
| Zone 6a | −10 °F to −5 °F | 12% (51) | Torrington, Litchfield |
| Zone 6b | −5 °F to 0 °F | 60% (252) | Hartford, Waterbury, Danbury, New Britain |
| Zone 7a | 0 °F to 5 °F | 27% (113) | Bridgeport, Stamford, New Haven, Norwalk |
| Zone 7b | 5 °F to 10 °F | <1% (3) | 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 Connecticut Gardeners?
A Connecticut gardener in zone 7b sees winter lows about 15 °F milder than one in zone 6a, 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 Connecticut, a plant labelled “zones 6–7” survives winter in at least 99% 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 Connecticut towns in the same zone can have last frosts weeks apart.
What Plants Grow Well Across Connecticut?
219 plants in PlantoScan's catalogue are hardy in every zone from 6a to 7a, the zones that cover 99% of Connecticut 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
Azalea
Azalea indica
Zone 6a – 9b
AI generated
Arugula
Eruca sativa
Zone 5a – 10b
AI generated
Hardiness ranges come from PlantoScan's plant database; gardeners in Connecticut's colder or warmer edge zones should check each plant's full range.
When Is the Last Frost in Connecticut?
Across most Connecticut ZIP codes, the average last spring frost falls between April 12 and May 3, from April 5 in Bridgeport to May 8 in Bantam. Tender vegetables such as tomatoes go out 1 to 2 weeks after the local date.
The last and first frost dates for Connecticut 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 Connecticut?
- Connecticut spans USDA hardiness zones 6a to 7b on the 2023 USDA Plant Hardiness Zone Map. Zone 6b is the most common, covering 60% of the state's 419 ZIP codes, and zones 6a to 7a together cover 99%.
- What hardiness zone is Bridgeport, Connecticut?
- Bridgeport is in USDA hardiness zone 7a (ZIP 06608), where the average coldest winter night reaches 0 °F to 5 °F. Its average last spring frost is April 5 and its first fall frost November 6.
- What hardiness zone is Stamford, Connecticut?
- Stamford is in USDA hardiness zone 7a (ZIP 06905), where the average coldest winter night reaches 0 °F to 5 °F. Its average last spring frost is April 17 and its first fall frost October 23.
- What hardiness zone is New Haven, Connecticut?
- New Haven is in USDA hardiness zone 7a (ZIP 06510), where the average coldest winter night reaches 0 °F to 5 °F. Its average last spring frost is April 17 and its first fall frost October 27.
- What is the coldest hardiness zone in Connecticut?
- Zone 6a (−10 °F to −5 °F) is the coldest zone in Connecticut, found in 51 ZIP codes around Torrington and Litchfield. The warmest is zone 7b (5 °F to 10 °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.