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When to Plant Soybeans in Foster County, ND

Foster County, North Dakota Zone 4a May

May in Foster County, North Dakota — your action list

Each item below is timed to Foster County, North Dakota's frost dates and soil temperatures. Skip nothing, stress about nothing.

Avg. last frost May 10
Avg. first frost September 30
Soil temp (4") 52°F
Watering Low
Pest pressure Low
Daylight 14.9 hrs
  1. Put soybeans seeds straight in the ground

    Rake a smooth bed, make a shallow furrow, drop seeds at the spacing on the packet, water gently, walk away.

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Soybeans (edamame) are a high-protein legume that fixes nitrogen in the soil. Fresh green soybeans harvested at the edamame stage are a nutritious snack.

Foster County, North Dakota is in USDA Zone 4a. The average last spring frost is May 10 and the first fall frost is September 30, giving you a growing season of approximately 143 days.

At an elevation of 895 feet, Foster County receives approximately 27.7 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Soybeans to ensure they mature before fall.

Foster County, ND (Zone 4a) Short season
143 days
Last Spring Frost May 10
143 growing days
First Fall Frost September 30
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Foster County Soil Profile

Soil Type

Loam

Soil pH

6.5-7.5

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (6 days to spare)
Transplant: May 1 🍅 Harvest: Jul 24 – Sep 18
Recommended (50%) ✓ Fits season (3 days to spare)
Transplant: May 10 🍅 Harvest: Aug 2 – Sep 27
Safe Start (90%) ✓ Fits season (8 days to spare)
Transplant: May 19 🍅 Harvest: Aug 11 – Oct 6

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 Foster County

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

Soil pH

Your soil pH (6.5–7.5) overlaps with Soybeans's range (6.0–7.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is excellent (4.0%) — Soybeans will thrive.

How to Plant Soybeans

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.8″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 285 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Soybeans

Soybeans needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Soybeans Needs Rainfall You Supplement Action
Jan 0.7" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.6" 0" ❄️ Dormant
Apr 3.1" 0" ❄️ Dormant
May 4.3" 4.6" 0" ✅ Rainfall sufficient
Jun 4.3" 4.2" 0.1" 💧 Light watering
Jul 4.3" 3.8" 0.5" 💧 Light watering
Aug 4.3" 3.1" 1.2" 💧 Light watering
Sep 4.3" 2.4" 1.9" 💧 Light watering
Oct 1.7" 0" ❄️ Dormant
Nov 0.8" 0" ❄️ Dormant
Dec 0.8" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Foster County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Soybeans 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.

Soybeans needs ~1,075 GDD — county provides 1,537 GDD Excellent fit

Soybeans Planting Timeline — Foster County, ND

Soybeans Planting Calendar

Activity When Date Range
Direct Sow May 24 May 24 – Jun 14
Harvest August 16 Aug 16 – Oct 11

Plant 1" deep · 15" apart · Rows 24" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April
May Direct Sow
June Direct Sow
July
August Harvest
September Harvest
October Harvest
November
December
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Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Only during dry spells

📅 Days to Maturity

80–120 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 4a

📆 Growing Season

143 days in Foster County

Growing Tips for Soybeans in Foster County

Direct sow Soybeans outdoors after May 10 in Foster County when soil has warmed and frost danger has passed.

Common pests for Soybeans in this region include bean beetles and aphids. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow after soil warms to 60F. Plant in blocks rather than rows for better pollination. Harvest for edamame when pods are plump and bright green.

Companion Planting

Good Companions

Avoid Planting Near

  • Onion
  • Garlic

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Soybeans in Foster County, ND?

Foster County is in Zone 4a with an average last frost of May 10. Plan your Soybeans planting based on this frost date — see the calendar above for exact timing.

What planting zone is Foster County, ND?

Foster County, North Dakota is in USDA Hardiness Zone 4a. The average last spring frost is May 10 and first fall frost is September 30.

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Your Foster County Garden Planner — Free

A 24-page printable planner built for Foster 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 Foster 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.