Portland, ME planting zone & frost dates
Portland is in USDA hardiness zone 6a. The last spring frost usually comes around April 26 and the first fall frost around October 15, for a growing season of about 170 days.
Planting calendar for Portland
Dates are counted from the average last spring frost (April 26) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Mar 1 – Mar 15 Transplant outdoors: May 3 – May 10 |
| Peppers | Start seeds indoors: Feb 15 – Mar 1 Transplant outdoors: May 10 – May 17 |
| Eggplant | Start seeds indoors: Feb 15 – Mar 1 Transplant outdoors: May 10 – May 17 |
| Broccoli | Start seeds indoors: Feb 15 – Mar 1 Transplant outdoors: Mar 29 – Apr 12 |
| Cabbage | Start seeds indoors: Feb 15 – Mar 1 Transplant outdoors: Mar 29 – Apr 12 |
| Onions (sets) | Plant outdoors: Mar 29 – Apr 12 |
| Peas | Sow outdoors: Mar 15 – Mar 29 |
| Spinach | Sow outdoors: Mar 15 – Mar 29 |
| Lettuce | Sow outdoors: Mar 29 – Apr 12 |
| Carrots | Sow outdoors: Mar 29 – Apr 12 |
| Potatoes | Plant outdoors: Mar 29 – Apr 12 |
| Beans | Sow outdoors: May 3 – May 10 |
| Sweet corn | Sow outdoors: May 3 – May 10 |
| Cucumbers | Sow outdoors: May 3 – May 10 |
| Squash & zucchini | Sow outdoors: May 3 – May 10 |
| Basil | Start seeds indoors: Mar 15 – Mar 29 Transplant outdoors: May 3 – May 10 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 20 (8 weeks before the average first fall frost on Oct 15).
Useful for zone 6a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 16 | Apr 26 | May 7 |
| First 32°F frost in fall is before | Oct 30 | Oct 15 | Oct 2 |
How to read it: in spring there is a 10% chance of a frost after May 7, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 2. A hard freeze (28°F) usually ends around April 14.
Hardiness zone by ZIP code in Portland
- 04101 zone 6a
- 04102 zone 6a
- 04103 zone 6a
- 04104 zone 6a
- 04109 zone 6a
- 04112 zone 6a
- 04122 zone 6a
- 04123 zone 6a
- 04124 zone 6a
Nearby cities
- South Portland zone 6a, last frost Apr 26
- South Portland Gardens zone 6a, last frost Apr 26
- Westbrook zone 5b, last frost Apr 26
- West Scarborough zone 6a, last frost Apr 26
- Saco zone 5b, last frost May 9
- Biddeford zone 5b, last frost May 9
- Brunswick zone 5b, last frost May 2
- Auburn zone 5b, last frost Apr 25
Questions
What growing zone is Portland, ME?
Portland is in USDA Plant Hardiness Zone 6a (average extreme winter low -10°F to -5°F), according to the USDA 2023 map.
When is the last frost in Portland?
The average last spring frost (32°F) in Portland is April 26. There is still a 10% chance of frost until May 7.
When can I plant tomatoes in Portland?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 3 – May 10. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Portland Intl Jetport, ME (USW00014764), 3.4 km (2.1 mi) from the city center, elevation 14 m, based on 30 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.