When to Plant Onion in Caldwell County, MO
Onions are a fundamental kitchen staple available in yellow, white, and red varieties. Choose long-day, short-day, or intermediate types based on your latitude.
Caldwell County, Missouri is in USDA Zone 5b. The average last spring frost is April 13 and the first fall frost is October 22, giving you a growing season of approximately 192 days.
At an elevation of 1,389 feet, Caldwell County receives approximately 34 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Onion to ensure they mature before fall.
Caldwell County Soil Profile
Soil Type
Silt Loam
Soil pH
5.6-7.1
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Plant Water Budget
Onion Planting Timeline — Caldwell County, MO
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 9 | Mar 9 – Mar 23 |
| Transplant Outdoors | April 13 | Apr 13 – Apr 27 |
| Direct Sow | March 30 | Mar 30 – Apr 20 |
| Fall Sowing | August 13 | Aug 13 – Aug 27 |
| Harvest | July 13 | Jul 13 – Aug 31 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | — |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
90–120 days
Soil pH
6 – 7
USDA Zone
Zone 5b
Growing Season
192 days
Growing Tips for Caldwell County
Start seeds indoors 8-10 weeks before transplanting. Match day-length type to your latitude. Stop watering when tops begin to fall over and cure bulbs for 2-3 weeks before storage.
Companion Planting
Good Companions
Avoid Planting Near
Level Up Your Garden
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Caldwell County, MO?
Caldwell County is in Zone 5b with an average last frost of April 13. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Caldwell County, MO?
Caldwell County, Missouri is in USDA Hardiness Zone 5b. The average last spring frost is April 13 and first fall frost is October 22.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Caldwell County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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