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When to Plant Thyme in Grand Forks County, ND

Grand Forks County, North Dakota Zone 4a May

This month in Grand Forks County, North Dakota

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

Avg. last frost May 11
Avg. first frost September 30
Soil temp (4") 51°F
Watering Low
Pest pressure Low
Daylight 15 hrs
  1. Move thyme into the garden

    Plant tomatoes deep — bury the stem up to the first true leaves to grow extra roots. Everything else goes in at the same depth it grew in the tray.

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Thyme is a low-growing perennial herb with tiny, aromatic leaves and a warm, earthy flavor. It is one of the most versatile culinary and medicinal herbs.

Grand Forks County, North Dakota is in USDA Zone 4a. The average last spring frost is May 11 and the first fall frost is September 30, giving you a growing season of approximately 142 days.

At an elevation of 572 feet, Grand Forks County receives approximately 27.7 inches of rainfall annually with predominantly loam soil. Summer highs average 79°F, so choose short-season varieties of Thyme to ensure they mature before fall.

Grand Forks County, ND (Zone 4a) Short season
142 days
Last Spring Frost May 11
142 growing days
First Fall Frost September 30
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Grand Forks County Soil Profile

Soil Type

Loam

Soil pH

6.8-7.4

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (3 days to spare)
Transplant: May 11 🍅 Harvest: Jul 20 – Sep 21
Recommended (50%) ✓ Fits season (2 days to spare)
Transplant: May 18 🍅 Harvest: Jul 27 – Sep 28
Safe Start (90%) ✓ Fits season (4 days to spare)
Transplant: May 30 🍅 Harvest: Aug 8 – Oct 10

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 Grand Forks County

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

Soil pH

Your soil pH (6.8–7.4) is within Thyme's preferred range (6.0–8.0).

Soil Texture

The loam soil in Grand Forks County is excellent for Thyme — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (3.3%). Annual compost additions will help Thyme.

How to Plant Thyme

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

Succession Planting Thyme

2
successive plantings in your 142-day season

Sow every 8 weeks. Last sowing by Jul 02 to harvest before frost.

Plant Water Budget

Plant needs
0.3″/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 Thyme

Thyme needs approximately 0.3 inches of water per week (1.3" per month). Here's how your county's rainfall compares month by month.

Month Thyme Needs Rainfall You Supplement Action
Jan 0.8" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.9" 0" ❄️ Dormant
Apr 3.2" 0" ❄️ Dormant
May 1.3" 4.1" 0" ✅ Rainfall sufficient
Jun 1.3" 4.6" 0" ✅ Rainfall sufficient
Jul 1.3" 3" 0" ✅ Rainfall sufficient
Aug 1.3" 3.6" 0" ✅ Rainfall sufficient
Sep 1.3" 2.5" 0" ✅ Rainfall sufficient
Oct 1.8" 0" ❄️ Dormant
Nov 0.8" 0" ❄️ Dormant
Dec 0.6" 0" ❄️ Dormant

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

Thyme 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.

Thyme needs ~740 GDD — county provides 1,313 GDD Excellent fit

Thyme Planting Timeline — Grand Forks County, ND

Thyme Planting Calendar

Activity When Date Range
Transplant Outdoors May 18 May 18 – Jun 1
Harvest July 27 Jul 27 – Sep 28

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

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.3"/week · Natural rainfall sufficient

📅 Days to Maturity

70–90 days

🧪 Soil pH

Needs 6–8 · Your soil: ideal

🗺️ USDA Zone

Zone 4a

📆 Growing Season

142 days in Grand Forks County

Growing Tips for Thyme in Grand Forks County

Direct sow Thyme outdoors after May 11 in Grand Forks County when soil has warmed and frost danger has passed.

General growing tips

Start from seed, cuttings, or divisions. Plant in well-drained, lean soil. Prune lightly after flowering. Replace plants every 3-4 years when they become woody.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Thyme in Grand Forks County, ND?

Grand Forks County is in Zone 4a with an average last frost of May 11. Plan your Thyme planting based on this frost date — see the calendar above for exact timing.

What planting zone is Grand Forks County, ND?

Grand Forks County, North Dakota is in USDA Hardiness Zone 4a. The average last spring frost is May 11 and first fall frost is September 30.

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Your Grand Forks County Garden Planner — Free

A 24-page printable planner built for Grand Forks 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 Grand Forks 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.