When to plant Onion in Thomas County, KS
Thomas County sits in USDA Zone 6a. Plant Onion between April 16 (after last frost on April 30) and May 7. A second sowing from August 3 to August 17 extends the harvest into fall.
When to Plant Onion in Thomas County, KS
Your August planting checklist for Thomas County, Kansas
Welcome to August in Zone 6a. These are the moves that will have the biggest impact on your growing season.
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Harvest onion as they ripen
Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.
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Plant your fall garden: onion
Fall crops get sweeter with a light frost. Don't be afraid of cool nights.
Looking ahead to September
- First harvests: onion
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 6a. 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
Onion 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.
Soil Compatibility in Thomas County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (6.8–7.5) is more alkaline than Onion prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Thomas County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.1%) — Onion will thrive.
How to Plant Onion
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Onion Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Onion
Onion needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Onion Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 2.1" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.2" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| May | 4.3" | 3.2" | 1.1" | 💧 Light watering |
| Jun | 4.3" | 2" | 2.3" | 🚿 Regular watering |
| Jul | 4.3" | 2.3" | 2" | 💧 Light watering |
| Aug | 4.3" | 2.6" | 1.7" | 💧 Light watering |
| Sep | 4.3" | 2.1" | 2.2" | 🚿 Regular watering |
| Oct | 4.3" | 2.3" | 2" | 💧 Light watering |
| Nov | — | 1.7" | 0" | ❄️ Dormant |
| Dec | — | 1.5" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Thomas County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
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 |
| Harvest | July 30 | Jul 30 – Sep 17 |
| Fall Sowing | August 3 | Aug 3 – Aug 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
1"/week · 1-2 times/week
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 6a
📆 Growing Season
165 days in Thomas County
Growing Tips for Onion in Thomas County
Direct sow Onion outdoors after April 30 in Thomas County when soil has warmed and frost danger has passed.
Common pests for Onion in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
General growing tips
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
Check more plant combinations with our Companion Planting Checker →
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Thomas County, KS?
Thomas County is in Zone 6a 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 6a. The average last spring frost is April 30 and first fall frost is October 12.
When should I plant Onion in Thomas County, KS?
In Thomas County, KS, plant Onion after the last frost (around April 30) and before the first frost (around October 12). Best results when soil holds above 50°F.
What growing zone is Thomas County, KS for Onion?
Thomas County sits in USDA Zone 6a. Onion grows reliably in zones 3a through 10b, so it's a good fit here.
Can Onion grow in Thomas County's climate?
Yes — Onion grows well in Thomas County's temperate climate. Thomas County averages a 165-day frost-free season, with last frost around April 30 and first frost around October 12.
Your Thomas County Garden Planner — Free
A 22-page printable planner built for Thomas County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.