Washington, MO planting zone & frost dates
Washington is in USDA hardiness zone 6b. The last spring frost usually comes around April 8 and the first fall frost around October 25, for a growing season of about 199 days.
Planting calendar for Washington
Dates are counted from the average last spring frost (April 8) 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: Feb 11 – Feb 25 Transplant outdoors: Apr 15 – Apr 22 |
| Peppers | Start seeds indoors: Jan 28 – Feb 11 Transplant outdoors: Apr 22 – Apr 29 |
| Eggplant | Start seeds indoors: Jan 28 – Feb 11 Transplant outdoors: Apr 22 – Apr 29 |
| Broccoli | Start seeds indoors: Jan 28 – Feb 11 Transplant outdoors: Mar 11 – Mar 25 |
| Cabbage | Start seeds indoors: Jan 28 – Feb 11 Transplant outdoors: Mar 11 – Mar 25 |
| Onions (sets) | Plant outdoors: Mar 11 – Mar 25 |
| Peas | Sow outdoors: Feb 25 – Mar 11 |
| Spinach | Sow outdoors: Feb 25 – Mar 11 |
| Lettuce | Sow outdoors: Mar 11 – Mar 25 |
| Carrots | Sow outdoors: Mar 11 – Mar 25 |
| Potatoes | Plant outdoors: Mar 11 – Mar 25 |
| Beans | Sow outdoors: Apr 15 – Apr 22 |
| Sweet corn | Sow outdoors: Apr 15 – Apr 22 |
| Cucumbers | Sow outdoors: Apr 15 – Apr 22 |
| Squash & zucchini | Sow outdoors: Apr 15 – Apr 22 |
| Basil | Start seeds indoors: Feb 25 – Mar 11 Transplant outdoors: Apr 15 – Apr 22 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 30 (8 weeks before the average first fall frost on Oct 25).
Useful for zone 6b 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
As an Amazon Associate, FrostZoneMap earns from qualifying purchases, at no extra cost to you.
Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Mar 24 | Apr 8 | Apr 22 |
| First 32°F frost in fall is before | Nov 5 | Oct 25 | Oct 13 |
How to read it: in spring there is a 10% chance of a frost after April 22, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 13. A hard freeze (28°F) usually ends around March 29.
Hardiness zone by ZIP code in Washington
- 63090 zone 6b
Nearby cities
- Union zone 6b, last frost Apr 11
- Wentzville zone 6b, last frost Apr 10
- Lake Saint Louis zone 6b, last frost Apr 10
- Wildwood zone 7a, last frost Apr 12
- Dardenne Prairie zone 6b, last frost Apr 10
- Eureka zone 6b, last frost Apr 12
- O'Fallon zone 6b, last frost Apr 9
- Troy zone 6b, last frost Apr 14
Questions
What growing zone is Washington, MO?
Washington is in USDA Plant Hardiness Zone 6b (average extreme winter low -5°F to 0°F), according to the USDA 2023 map.
When is the last frost in Washington?
The average last spring frost (32°F) in Washington is April 8. There is still a 10% chance of frost until April 22.
When can I plant tomatoes in Washington?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Apr 15 – Apr 22. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Washington, MO (USC00238746), 3.7 km (2.3 mi) from the city center, elevation 148 m, based on 11 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.