When to Plant Onion in Robertson 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.
Robertson County, Texas is in USDA Zone 9a. The average last spring frost is March 7 and the first fall frost is November 16, giving you a growing season of approximately 254 days.
At an elevation of 85 feet, Robertson County receives approximately 61.1 inches of rainfall annually with predominantly clay soil. Summer highs average 93°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.
Robertson County Soil Profile
Soil Type
Clay
Soil pH
6.8-8
Drainage
Well Drained
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 | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 2.2" | 0" | ❄️ Dormant |
| Mar | 4.3" | 4.3" | 0" | ✅ Rainfall sufficient |
| Apr | 4.3" | 5.6" | 0" | ✅ Rainfall sufficient |
| May | 4.3" | 10" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 8.4" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 8.3" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 8.2" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 5.2" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 3.7" | 0.6" | 💧 Light watering |
| Nov | 4.3" | 2.3" | 2" | 💧 Light watering |
| Dec | — | 1.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Robertson County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion Planting Timeline — Robertson County, TX
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 7 | Feb 7 – Feb 21 |
| Transplant Outdoors | March 7 | Mar 7 – Mar 21 |
| Direct Sow | February 14 | Feb 14 – Mar 7 |
| Harvest | June 6 | Jun 6 – Jul 25 |
| Fall Sowing | September 21 | Sep 21 – Oct 5 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors Direct Sow |
| March | Transplant Outdoors Direct Sow |
| April | — |
| May | — |
| June | Harvest |
| July | Harvest |
| August | — |
| September | Fall Sowing |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 9a
📆 Growing Season
254 days in Robertson County
Growing Tips for Robertson 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
Check more plant combinations with our Companion Planting Checker →
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Robertson County, TX?
Robertson County is in Zone 9a with an average last frost of March 7. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Robertson County, TX?
Robertson County, Texas is in USDA Hardiness Zone 9a. The average last spring frost is March 7 and first fall frost is November 16.
Your Robertson County Garden Planner — Free
A 22-page printable planner built for Robertson County (Zone 9a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.