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When to Plant Basil in Foster County, ND

Foster County, North Dakota Zone 4a May

May in the garden — Foster County, North Dakota

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.

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. Get basil in the ground

    Pinch off the lowest leaves on each seedling before you plant — it reduces water loss while the roots catch up.

  2. Outdoor sowing time: basil

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

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Basil is a fragrant warm-season herb essential to Italian and Thai cuisines. It comes in many varieties including sweet, Thai, purple, and lemon types.

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 Basil 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

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)
Start indoors: Mar 6 Transplant: May 22 🍅 Harvest: Jul 17 – Sep 18
Recommended (50%) ✓ Fits season (3 days to spare)
Start indoors: Mar 15 Transplant: May 31 🍅 Harvest: Jul 26 – Sep 27
Safe Start (90%) ✓ Fits season (8 days to spare)
Start indoors: Mar 24 Transplant: Jun 9 🍅 Harvest: Aug 4 – 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 Basil's growing requirements.

Soil pH

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

Soil Texture

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

Organic Matter

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

How to Plant Basil

0.5"
Planting Depth
8"
Between Plants
12"
Between Rows

Succession Planting Basil

3
successive plantings in your 143-day season

Sow every 5.7 weeks. Last sowing by Jul 17 to harvest before frost.

Plant Water Budget

Plant needs
0.6″/week
Rainfall provides
0.8″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Basil

Basil needs approximately 0.6 inches of water per week (2.6" per month). Here's how your county's rainfall compares month by month.

Month Basil 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 2.6" 4.6" 0" ✅ Rainfall sufficient
Jun 2.6" 4.2" 0" ✅ Rainfall sufficient
Jul 2.6" 3.8" 0" ✅ Rainfall sufficient
Aug 2.6" 3.1" 0" ✅ Rainfall sufficient
Sep 2.6" 2.4" 0.2" 💧 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.

Basil 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.

Basil needs ~672 GDD — county provides 1,537 GDD Excellent fit

Basil Planting Timeline — Foster County, ND

Basil Planting Calendar

Activity When Date Range
Start Indoors March 15 Mar 15 – Mar 29
Transplant Outdoors May 31 May 31 – Jun 14
Direct Sow May 17 May 17 – Jun 7
Harvest July 26 Jul 26 – Sep 27

Plant 0.5" deep · 8" apart · Rows 12" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.6"/week · Natural rainfall sufficient

📅 Days to Maturity

50–75 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 4a

📆 Growing Season

143 days in Foster County

Growing Tips for Basil in Foster County

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

General growing tips

Start seeds indoors or direct sow after last frost. Pinch flower buds to extend leaf production. Harvest leaves from the top down, cutting just above a leaf pair.

Companion Planting

Good Companions

Avoid Planting Near

  • Rue
  • Sage

Check more plant combinations with our Companion Planting Checker →

🌾 Save Your Own Basil Seeds
Life Cycle Annual
Pollination Self-Pollinating
How to Collect Let flower spikes dry brown on the plant.
Storage Store airtight; viable 5 years at 35°F, under 45% humidity.

Isolate 150 ft between varieties. Different basil species can cross.

Frequently Asked Questions

When should I plant Basil in Foster County, ND?

Foster County is in Zone 4a with an average last frost of May 10. Plan your Basil 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.

🌱

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.