When to Plant Onion in Johnson County, TX
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.
Johnson County, Texas is in USDA Zone 8a. The average last spring frost is March 18 and the first fall frost is November 12, giving you a growing season of approximately 239 days.
At an elevation of 2,525 feet, Johnson County receives approximately 62.8 inches of rainfall annually with predominantly clay soil. Summer highs average 92°F, providing good warmth for Onion during the growing season. Clay soil retains moisture well for Onion, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Onion root diseases.
Johnson County Soil Profile
Soil Type
Clay
Soil pH
7-7.8
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 — Johnson County, TX
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 11 | Feb 11 – Feb 25 |
| Transplant Outdoors | March 18 | Mar 18 – Apr 1 |
| Direct Sow | March 4 | Mar 4 – Mar 25 |
| Fall Sowing | September 3 | Sep 3 – Sep 17 |
| Harvest | June 17 | Jun 17 – Aug 5 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Transplant Outdoors Direct Sow |
| April | Transplant Outdoors |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | Fall Sowing |
| 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 8a
Growing Season
239 days
Growing Tips for Johnson 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 Johnson County, TX?
Johnson County is in Zone 8a with an average last frost of March 18. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Johnson County, TX?
Johnson County, Texas is in USDA Hardiness Zone 8a. The average last spring frost is March 18 and first fall frost is November 12.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Johnson County gardeners in Zone 8a 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.