Alpena, MI planting zone & frost dates
Alpena is in USDA hardiness zone 5b. The last spring frost usually comes around May 5 and the first fall frost around October 17, for a growing season of about 163 days.
Planting calendar for Alpena
Dates are counted from the average last spring frost (May 5) 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 10 – Mar 24 Transplant outdoors: May 12 – May 19 |
| Peppers | Start seeds indoors: Feb 24 – Mar 10 Transplant outdoors: May 19 – May 26 |
| Eggplant | Start seeds indoors: Feb 24 – Mar 10 Transplant outdoors: May 19 – May 26 |
| Broccoli | Start seeds indoors: Feb 24 – Mar 10 Transplant outdoors: Apr 7 – Apr 21 |
| Cabbage | Start seeds indoors: Feb 24 – Mar 10 Transplant outdoors: Apr 7 – Apr 21 |
| Onions (sets) | Plant outdoors: Apr 7 – Apr 21 |
| Peas | Sow outdoors: Mar 24 – Apr 7 |
| Spinach | Sow outdoors: Mar 24 – Apr 7 |
| Lettuce | Sow outdoors: Apr 7 – Apr 21 |
| Carrots | Sow outdoors: Apr 7 – Apr 21 |
| Potatoes | Plant outdoors: Apr 7 – Apr 21 |
| Beans | Sow outdoors: May 12 – May 19 |
| Sweet corn | Sow outdoors: May 12 – May 19 |
| Cucumbers | Sow outdoors: May 12 – May 19 |
| Squash & zucchini | Sow outdoors: May 12 – May 19 |
| Basil | Start seeds indoors: Mar 24 – Apr 7 Transplant outdoors: May 12 – May 19 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 22 (8 weeks before the average first fall frost on Oct 17).
Useful for zone 5b 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 21 | May 5 | May 21 |
| First 32°F frost in fall is before | Nov 1 | Oct 17 | Sep 30 |
How to read it: in spring there is a 10% chance of a frost after May 21, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 30. A hard freeze (28°F) usually ends around April 23.
Hardiness zone by ZIP code in Alpena
- 49707 zone 5b
Nearby cities
- Bay City zone 6a, last frost Apr 27
- Midland zone 6a, last frost Apr 29
- Sault Ste. Marie zone 5a, last frost May 9
- Saginaw Township North zone 6a, last frost Apr 29
- Saginaw zone 6a, last frost Apr 29
- Mount Pleasant zone 6a, last frost Apr 30
- Beecher zone 6a, last frost May 3
- Flint zone 6a, last frost May 6
Questions
What growing zone is Alpena, MI?
Alpena is in USDA Plant Hardiness Zone 5b (average extreme winter low -15°F to -10°F), according to the USDA 2023 map.
When is the last frost in Alpena?
The average last spring frost (32°F) in Alpena is May 5. There is still a 10% chance of frost until May 21.
When can I plant tomatoes in Alpena?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 12 – May 19. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Alpena Wwtp, MI (USW00014814), 0.4 km (0.2 mi) from the city center, elevation 180 m, based on 28 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.