When to Plant Onion in Sutton 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.
Sutton County, Texas is in USDA Zone 8a. The average last spring frost is March 28 and the first fall frost is November 10, giving you a growing season of approximately 227 days.
At an elevation of 4,068 feet, Sutton County receives approximately 46 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 103°F, so Onion may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Onion will need more frequent watering and organic matter to retain nutrients.
Sutton County Soil Profile
Soil Type
Sandy Loam
Soil pH
7.8-8.7
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 Sutton County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (7.8–8.7) is more alkaline than Onion prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
Sandy soil in Sutton County warms quickly in spring but drains fast. Onion will need more frequent watering and regular compost additions to retain nutrients.
Organic Matter
Organic matter is low (1.0%). Add 2-3 inches of compost before planting Onion.
How to Plant Onion
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Plant Water Budget
Water stress score is 8/10 — 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 | — | 3.5" | 0" | ❄️ Dormant |
| Feb | — | 3" | 0" | ❄️ Dormant |
| Mar | 4.3" | 2.6" | 1.7" | 💧 Light watering |
| Apr | 4.3" | 1.7" | 2.6" | 🚿 Regular watering |
| May | 4.3" | 1" | 3.3" | 🚿 Regular watering |
| Jun | 4.3" | 1.6" | 2.7" | 🚿 Regular watering |
| Jul | 4.3" | 7.5" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 8.3" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 7.3" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 3.6" | 0.7" | 💧 Light watering |
| Nov | 4.3" | 2.5" | 1.8" | 💧 Light watering |
| Dec | — | 3.4" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Sutton 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 — Sutton County, TX
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 21 | Feb 21 – Mar 7 |
| Transplant Outdoors | March 28 | Mar 28 – Apr 11 |
| Direct Sow | March 14 | Mar 14 – Apr 4 |
| Harvest | June 27 | Jun 27 – Aug 15 |
| Fall Sowing | September 1 | Sep 1 – Sep 15 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors Transplant Outdoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | Fall Sowing |
| October | — |
| November | — |
| 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: too_alkaline
🗺️ USDA Zone
Zone 8a
📆 Growing Season
227 days in Sutton County
Growing Tips for Onion in Sutton County
Direct sow Onion outdoors after March 28 in Sutton County when soil has warmed and frost danger has passed.
Sandy soil in Sutton County dries quickly — mulch Onion with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 103°F in Sutton 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 Sutton County, TX?
Sutton County is in Zone 8a with an average last frost of March 28. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Sutton County, TX?
Sutton County, Texas is in USDA Hardiness Zone 8a. The average last spring frost is March 28 and first fall frost is November 10.
Plan Your Garden with Confidence
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