When to Plant Onion in Hidalgo 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.
Hidalgo County, Texas is in USDA Zone 9b. The average last spring frost is February 6 and the first fall frost is December 18, giving you a growing season of approximately 315 days.
At an elevation of 4,081 feet, Hidalgo County receives approximately 67 inches of rainfall annually with predominantly loam soil. Summer highs average 100°F, so Onion may need afternoon shade and extra watering during peak heat. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Onion root diseases.
Hidalgo County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.8
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.
Soil Compatibility in Hidalgo County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (6.2–7.8) overlaps with Onion's range (6.0–7.0), though not a perfect match.
Soil Texture
The loam soil in Hidalgo County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Onion.
How to Plant Onion
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Plant Water Budget
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 | 4.3" | 2.1" | 2.2" | 🚿 Regular watering |
| Mar | 4.3" | 3.6" | 0.7" | 💧 Light watering |
| Apr | 4.3" | 6.7" | 0" | ✅ Rainfall sufficient |
| May | 4.3" | 10.1" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 9.4" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 9.3" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 8.7" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 6.9" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Nov | 4.3" | 2.5" | 1.8" | 💧 Light watering |
| Dec | 4.3" | 1.8" | 2.5" | 🚿 Regular watering |
Water needs are for active growing months only (Feb–Dec in Hidalgo 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 — Hidalgo County, TX
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 9 | Jan 9 – Jan 23 |
| Transplant Outdoors | February 6 | Feb 6 – Feb 20 |
| Direct Sow | January 16 | Jan 16 – Feb 6 |
| Harvest | May 8 | May 8 – Jun 26 |
| Fall Sowing | October 23 | Oct 23 – Nov 6 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Direct Sow |
| February | Transplant Outdoors Direct Sow |
| March | — |
| April | — |
| May | Harvest |
| June | Harvest |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | Fall Sowing |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 9b
📆 Growing Season
315 days in Hidalgo County
Growing Tips for Onion in Hidalgo County
Direct sow Onion outdoors after February 06 in Hidalgo County when soil has warmed and frost danger has passed.
With summer highs reaching 100°F in Hidalgo County, provide afternoon shade for Onion and water deeply in the morning.
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
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Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Hidalgo County, TX?
Hidalgo County is in Zone 9b with an average last frost of February 6. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Hidalgo County, TX?
Hidalgo County, Texas is in USDA Hardiness Zone 9b. The average last spring frost is February 6 and first fall frost is December 18.
Plan Your Garden with Confidence
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