When to Plant Onion in San Miguel County, NM
What to do in May
Your garden in San Miguel County, New Mexico is working on a schedule, even when you're not. Here's where you should be this May.
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Transplant onion outside
Harden off for 7 days — a little more sun each day — before planting. That's the difference between a seedling that thrives and one that stalls.
June will be here before you know it — start on
- Starting indoors: 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.
San Miguel County, New Mexico is in USDA Zone 6b. The average last spring frost is May 10 and the first fall frost is October 7, giving you a growing season of approximately 150 days.
At an elevation of 7,435 feet, San Miguel County receives approximately 14.4 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 84°F, so choose short-season varieties of Onion to ensure they mature before fall. Sandy soil warms quickly in spring — great for early planting — but Onion will need more frequent watering and organic matter to retain nutrients. With low rainfall, drip irrigation is essential for growing Onion successfully. Mulch heavily to conserve soil moisture.
San Miguel County Soil Profile
Soil Type
Sandy Loam
Soil pH
7.2-8.5
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 San Miguel County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (7.2–8.5) is more alkaline than Onion prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
Sandy soil in San Miguel County warms quickly in spring but drains fast. Onion will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Onion.
Organic Matter
Organic matter is low (0.8%). 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 10/10 — 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 | — | 1.1" | 0" | ❄️ Dormant |
| Feb | — | 0.9" | 0" | ❄️ Dormant |
| Mar | — | 0.8" | 0" | ❄️ Dormant |
| Apr | — | 0.5" | 0" | ❄️ Dormant |
| May | 4.3" | 0.4" | 3.9" | 🚿 Regular watering |
| Jun | 4.3" | 0.5" | 3.8" | 🚿 Regular watering |
| Jul | 4.3" | 2.5" | 1.8" | 💧 Light watering |
| Aug | 4.3" | 2.7" | 1.6" | 💧 Light watering |
| Sep | 4.3" | 1.8" | 2.5" | 🚿 Regular watering |
| Oct | 4.3" | 1.3" | 3" | 🚿 Regular watering |
| Nov | — | 0.9" | 0" | ❄️ Dormant |
| Dec | — | 1.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in San Miguel 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 — San Miguel County, NM
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 5 | Apr 5 – Apr 19 |
| Transplant Outdoors | May 10 | May 10 – May 24 |
| Direct Sow | April 26 | Apr 26 – May 17 |
| Harvest | August 9 | Aug 9 – Sep 27 |
| Fall Sowing | July 29 | Jul 29 – Aug 12 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Fall Sowing |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 2-3 times/week
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 6b
📆 Growing Season
150 days in San Miguel County
Growing Tips for Onion in San Miguel County
Direct sow Onion outdoors after May 10 in San Miguel County when soil has warmed and frost danger has passed.
Sandy soil in San Miguel County dries quickly — mulch Onion with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
Common pests for Onion in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
San Miguel County receives only 14" of rain annually. Onion needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
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 San Miguel County, NM?
San Miguel County is in Zone 6b with an average last frost of May 10. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is San Miguel County, NM?
San Miguel County, New Mexico is in USDA Hardiness Zone 6b. The average last spring frost is May 10 and first fall frost is October 7.
Your San Miguel County Garden Planner — Free
A 24-page printable planner built for San Miguel County (Zone 6b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.