Ann Arbor, MI planting zone & frost dates
Ann Arbor is in USDA hardiness zone 6a. The last spring frost usually comes around May 5 and the first fall frost around October 10, for a growing season of about 157 days.
Planting calendar for Ann Arbor
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 15 (8 weeks before the average first fall frost on Oct 10).
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 21 | May 5 | May 20 |
| First 32°F frost in fall is before | Oct 24 | Oct 10 | Sep 28 |
How to read it: in spring there is a 10% chance of a frost after May 20, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 28. A hard freeze (28°F) usually ends around April 24.
Hardiness zone by ZIP code in Ann Arbor
- 48103 zone 6a
- 48104 zone 6a
- 48105 zone 6a
- 48106 zone 6a
- 48107 zone 6a
- 48108 zone 6a
- 48109 zone 6a
- 48113 zone 6a
Nearby cities
Questions
What growing zone is Ann Arbor, MI?
Ann Arbor 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 Ann Arbor?
The average last spring frost (32°F) in Ann Arbor is May 5. There is still a 10% chance of frost until May 20.
When can I plant tomatoes in Ann Arbor?
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 Ann Arbor Se, MI (USC00200228), 5.6 km (3.5 mi) from the city center, elevation 254 m, based on 17 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.