When to Plant Scallions in Yuma County, AZ
This month in Yuma County, Arizona
If you only do a handful of things in the garden this May, make it these. They're sequenced around your zone's frost timing.
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Start harvesting scallions
Check every 1–2 days. Many of these get tough or go to seed if you wait too long.
Scallions (green onions) are mild-flavored alliums harvested for their slender green tops and white bases. They are quick-growing and perfect for succession planting.
Yuma County, Arizona is in USDA Zone 10a. The average last spring frost is February 10 and the first fall frost is December 1, giving you a growing season of approximately 294 days.
At an elevation of 4,781 feet, Yuma County receives approximately 9.4 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 92°F, providing good warmth for Scallions during the growing season. Sandy soil warms quickly in spring — great for early planting — but Scallions will need more frequent watering and organic matter to retain nutrients. With low rainfall, drip irrigation is essential for growing Scallions successfully. Mulch heavily to conserve soil moisture.
Yuma County Soil Profile
Soil Type
Sandy Loam
Soil pH
6.9-8.4
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 Yuma County
How your county's soil matches Scallions's growing requirements.
Soil pH
Your soil pH (6.9–8.4) is more alkaline than Scallions prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
Sandy soil in Yuma County warms quickly in spring but drains fast. Scallions will need more frequent watering and regular compost additions to retain nutrients.
Organic Matter
Organic matter is low (0.8%). Add 2-3 inches of compost before planting Scallions.
How to Plant Scallions
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Succession Planting Scallions
Sow every 5.7 weeks. Last sowing by Sep 22 to harvest before frost.
For a dedicated fall crop, sow by Oct 06.
Plant Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Scallions
Scallions needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Scallions Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 0.6" | 0" | ❄️ Dormant |
| Feb | 4.3" | 0.5" | 3.8" | 🚿 Regular watering |
| Mar | 4.3" | 0.5" | 3.8" | 🚿 Regular watering |
| Apr | 4.3" | 0.3" | 4" | 🚿 Regular watering |
| May | 4.3" | 0.2" | 4.1" | 🚿 Regular watering |
| Jun | 4.3" | 0.3" | 4" | 🚿 Regular watering |
| Jul | 4.3" | 1.8" | 2.5" | 🚿 Regular watering |
| Aug | 4.3" | 1.9" | 2.4" | 🚿 Regular watering |
| Sep | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| Oct | 4.3" | 0.8" | 3.5" | 🚿 Regular watering |
| Nov | 4.3" | 0.5" | 3.8" | 🚿 Regular watering |
| Dec | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
Water needs are for active growing months only (Feb–Dec in Yuma County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Scallions 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.
Scallions Planting Timeline — Yuma County, AZ
Scallions Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 13 | Jan 13 – Jan 27 |
| Transplant Outdoors | February 10 | Feb 10 – Feb 24 |
| Direct Sow | January 20 | Jan 20 – Feb 10 |
| Harvest | April 7 | Apr 7 – May 5 |
| Fall Sowing | October 6 | Oct 6 – Oct 20 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Direct Sow |
| February | Transplant Outdoors Direct Sow |
| March | — |
| April | Harvest |
| May | Harvest |
| June | — |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 2-3 times/week
📅 Days to Maturity
50–70 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 10a
📆 Growing Season
294 days in Yuma County
Growing Tips for Scallions in Yuma County
Direct sow Scallions outdoors after February 10 in Yuma County when soil has warmed and frost danger has passed.
Sandy soil in Yuma County dries quickly — mulch Scallions with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
Common pests for Scallions in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
Yuma County receives only 9" of rain annually. Scallions needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Direct sow every 3 weeks for continuous harvest. Thin to 1 inch apart or grow in clusters. Harvest when pencil-thick by pulling or cutting at soil level.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Scallions in Other Locations
Frequently Asked Questions
When should I plant Scallions in Yuma County, AZ?
Yuma County is in Zone 10a with an average last frost of February 10. Plan your Scallions planting based on this frost date — see the calendar above for exact timing.
What planting zone is Yuma County, AZ?
Yuma County, Arizona is in USDA Hardiness Zone 10a. The average last spring frost is February 10 and first fall frost is December 1.
Your Yuma County Garden Planner — Free
A 24-page printable planner built for Yuma County (Zone 10a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.