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When to Plant Onion in Eddy County, ND

Eddy County, North Dakota Zone 4a May

Your May game plan for Eddy County, North Dakota

Your Eddy County, North Dakota garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.

Avg. last frost May 13
Avg. first frost September 27
Soil temp (4") 51°F
Watering Low
Pest pressure Low
Daylight 14.9 hrs
  1. Time to transplant onion

    Your last frost (May 13) has passed. These warm-season crops can handle outdoor soil now.

  2. Plant onion from seed, right in the garden

    Sow every 2 weeks for a continuous harvest. A single big planting means a single big glut.

Before June arrives, get these ready
  • Starting indoors: onion

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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.

Eddy County, North Dakota is in USDA Zone 4a. The average last spring frost is May 13 and the first fall frost is September 27, giving you a growing season of approximately 137 days.

At an elevation of 864 feet, Eddy County receives approximately 29.3 inches of rainfall annually with predominantly loam soil. Summer highs average 78°F, so choose short-season varieties of Onion to ensure they mature before fall.

Eddy County, ND (Zone 4a) Short season
137 days
Last Spring Frost May 13
137 growing days
First Fall Frost September 27
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Eddy County Soil Profile

Soil Type

Loam

Soil pH

6.4-7.4

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 26 Transplant: May 7 🍅 Harvest: Aug 6 – Sep 24
Recommended (50%) ✗ May not fit
Start indoors: Apr 1 Transplant: May 13 🍅 Harvest: Aug 12 – Sep 30
Safe Start (90%) ✓ Fits season (0 days to spare)
Start indoors: Apr 13 Transplant: May 25 🍅 Harvest: Aug 24 – Oct 12

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 Eddy County

How your county's soil matches Onion's growing requirements.

Soil pH

Your soil pH (6.4–7.4) overlaps with Onion's range (6.0–7.0), though not a perfect match.

Soil Texture

The loam soil in Eddy County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (3.6%). Annual compost additions will help Onion.

How to Plant Onion

1"
Planting Depth
6"
Between Plants
12"
Between Rows

Fall planting: Sow 12 weeks before your first frost date for a fall harvest.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.9″/week
You supply
0.1″/week
Watering frequency Only during dry spells
Season total 149 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — 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 0.7" 0" ❄️ Dormant
Feb 0.9" 0" ❄️ Dormant
Mar 2.2" 0" ❄️ Dormant
Apr 3" 0" ❄️ Dormant
May 4.3" 4.8" 0" ✅ Rainfall sufficient
Jun 4.3" 4.3" 0" ✅ Rainfall sufficient
Jul 4.3" 3.5" 0.8" 💧 Light watering
Aug 4.3" 3.7" 0.6" 💧 Light watering
Sep 4.3" 2.4" 1.9" 💧 Light watering
Oct 2.1" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 0.8" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Eddy 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 needs ~892 GDD — county provides 1,164 GDD Excellent fit

Onion Planting Timeline — Eddy County, ND

Onion Planting Calendar

Activity When Date Range
Start Indoors April 1 Apr 1 – Apr 15
Transplant Outdoors May 13 May 13 – May 27
Direct Sow May 6 May 6 – May 27
Harvest August 12 Aug 12 – Sep 30
Fall Sowing July 5 Jul 5 – Jul 19

Plant 1" deep · 6" apart · Rows 12" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April Start Indoors
May Transplant Outdoors Direct Sow
June
July Fall Sowing
August Harvest
September Harvest
October
November
December
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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 4a

📆 Growing Season

137 days in Eddy County

Growing Tips for Onion in Eddy County

Direct sow Onion outdoors after May 13 in Eddy County when soil has warmed and frost danger has passed.

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

Good Companions

Avoid Planting Near

  • Peas
  • Green Beans
  • Asparagus

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Onion in Eddy County, ND?

Eddy County is in Zone 4a with an average last frost of May 13. Plan your Onion planting based on this frost date — see the calendar above for exact timing.

What planting zone is Eddy County, ND?

Eddy County, North Dakota is in USDA Hardiness Zone 4a. The average last spring frost is May 13 and first fall frost is September 27.

🌱

Your Eddy County Garden Planner — Free

A 24-page printable planner built for Eddy County (Zone 4a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Eddy County, ND. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.