Owosso, MI planting zone & frost dates
Owosso is in USDA hardiness zone 6a. The last spring frost usually comes around May 1 and the first fall frost around October 15, for a growing season of about 164 days.
Planting calendar for Owosso
Dates are counted from the average last spring frost (May 1) 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 6 – Mar 20 Transplant outdoors: May 8 – May 15 |
| Peppers | Start seeds indoors: Feb 20 – Mar 6 Transplant outdoors: May 15 – May 22 |
| Eggplant | Start seeds indoors: Feb 20 – Mar 6 Transplant outdoors: May 15 – May 22 |
| Broccoli | Start seeds indoors: Feb 20 – Mar 6 Transplant outdoors: Apr 3 – Apr 17 |
| Cabbage | Start seeds indoors: Feb 20 – Mar 6 Transplant outdoors: Apr 3 – Apr 17 |
| Onions (sets) | Plant outdoors: Apr 3 – Apr 17 |
| Peas | Sow outdoors: Mar 20 – Apr 3 |
| Spinach | Sow outdoors: Mar 20 – Apr 3 |
| Lettuce | Sow outdoors: Apr 3 – Apr 17 |
| Carrots | Sow outdoors: Apr 3 – Apr 17 |
| Potatoes | Plant outdoors: Apr 3 – Apr 17 |
| Beans | Sow outdoors: May 8 – May 15 |
| Sweet corn | Sow outdoors: May 8 – May 15 |
| Cucumbers | Sow outdoors: May 8 – May 15 |
| Squash & zucchini | Sow outdoors: May 8 – May 15 |
| Basil | Start seeds indoors: Mar 20 – Apr 3 Transplant outdoors: May 8 – May 15 |
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 17 | May 1 | May 17 |
| First 32°F frost in fall is before | Oct 30 | Oct 15 | Oct 1 |
How to read it: in spring there is a 10% chance of a frost after May 17, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 1. A hard freeze (28°F) usually ends around April 20.
Hardiness zone by ZIP code in Owosso
- 48867 zone 6a
Nearby cities
Questions
What growing zone is Owosso, MI?
Owosso 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 Owosso?
The average last spring frost (32°F) in Owosso is May 1. There is still a 10% chance of frost until May 17.
When can I plant tomatoes in Owosso?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 8 – May 15. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Owosso Wwtp, MI (USC00206300), 2.1 km (1.3 mi) from the city center, elevation 222 m, based on 26 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.