When to Plant Onions in Connecticut
In Connecticut, the time to plant onions outside runs from Mar 8 – Mar 22 in Bridgeport to Apr 10 – Apr 24 in Torrington. In Bridgeport, it's Mar 8 – Mar 22. The average last spring frost differs by about 5 weeks across the state (Apr 5 in Bridgeport, May 8 in Torrington), so use the dates for the town nearest you.
Onions are cold-hardy. Plant sets or transplants early so they grow leaves before long summer days trigger bulbing.
- Start indoors: 10–12 weeks before the last frost.
- Plant outside: 2–4 weeks before the last frost.
Onions planting dates in Connecticut by city
| City | Zone | Start indoors | Plant outside |
|---|---|---|---|
| Ansonia | 6b | Jan 31 – Feb 14 | Mar 28 – Apr 11 |
| Bridgeport | 7a | Jan 11 – Jan 25 | Mar 8 – Mar 22 |
| Bristol | 6b | Jan 31 – Feb 14 | Mar 28 – Apr 11 |
| Danbury | 6b | Feb 6 – Feb 20 | Apr 3 – Apr 17 |
| Derby | 6b | Jan 31 – Feb 14 | Mar 28 – Apr 11 |
| Groton | 7a | Jan 22 – Feb 5 | Mar 19 – Apr 2 |
| Hartford | 6b | Jan 23 – Feb 6 | Mar 20 – Apr 3 |
| Meriden | 6b | Feb 1 – Feb 15 | Mar 29 – Apr 12 |
| Middletown | 6b | Feb 1 – Feb 15 | Mar 29 – Apr 12 |
| Milford city | 7a | Jan 11 – Jan 25 | Mar 8 – Mar 22 |
| Naugatuck | 6b | Jan 24 – Feb 7 | Mar 21 – Apr 4 |
| New Britain | 6b | Jan 23 – Feb 6 | Mar 20 – Apr 3 |
| New Haven | 7a | Jan 23 – Feb 6 | Mar 20 – Apr 3 |
| New London | 7a | Jan 22 – Feb 5 | Mar 19 – Apr 2 |
| Norwalk | 7a | Jan 23 – Feb 6 | Mar 20 – Apr 3 |
| Norwich | 6b | Jan 20 – Feb 3 | Mar 17 – Mar 31 |
| Shelton | 6b | Jan 31 – Feb 14 | Mar 28 – Apr 11 |
| Stamford | 7a | Jan 23 – Feb 6 | Mar 20 – Apr 3 |
| Torrington | 6a | Feb 13 – Feb 27 | Apr 10 – Apr 24 |
| Waterbury | 6b | Feb 1 – Feb 15 | Mar 29 – Apr 12 |
| West Haven | 7a | Jan 23 – Feb 6 | Mar 20 – Apr 3 |
Calculated from each town's average (50%) frost dates, from the nearest NOAA station (1991–2020). Typical dates for the 2027 planting season, based on NOAA's 1991–2020 averages. They are long-term odds, not a forecast: always check your local forecast before planting. Zones: 2023 USDA Plant Hardiness Zone Map (USDA-ARS and Oregon State University). Not the official map; see planthardiness.ars.usda.gov.
See all frost dates in Connecticut, or the general guide to when to plant onions.
Getting beds ready? Work out how much raised bed soil, compost or mulch you need with our sister site, Yard Coverage.