When to Plant Onion in Thomas County, KS
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.
Thomas County, Kansas is in USDA Zone 5b. The average last spring frost is April 30 and the first fall frost is October 12, giving you a growing season of approximately 165 days.
At an elevation of 810 feet, Thomas County receives approximately 26.4 inches of rainfall annually with predominantly loam soil. Summer highs average 88°F, providing good warmth for Onion during the growing season.
Thomas County Soil Profile
Soil Type
Loam
Soil pH
6.8-7.5
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
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Onion Planting Timeline — Thomas County, KS
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 26 | Mar 26 – Apr 9 |
| Transplant Outdoors | April 30 | Apr 30 – May 14 |
| Direct Sow | April 16 | Apr 16 – May 7 |
| Fall Sowing | August 3 | Aug 3 – Aug 17 |
| Harvest | July 30 | Jul 30 – Sep 17 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| 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
165 days
Growing Tips for Thomas 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 Thomas County, KS?
Thomas County is in Zone 5b with an average last frost of April 30. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Thomas County, KS?
Thomas County, Kansas is in USDA Hardiness Zone 5b. The average last spring frost is April 30 and first fall frost is October 12.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Thomas County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.