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When to Plant Basil in Carlton County, MN

Carlton County, Minnesota Zone 4a May

This month in Carlton County, Minnesota

Here's what deserves your attention in Carlton County, Minnesota this month. Everything below is tailored to Zone 4a and timed around your local frost dates.

Avg. last frost May 12
Avg. first frost October 2
Soil temp (4") 49°F
Watering Moderate
Pest pressure Low
Daylight 14.8 hrs
  1. Direct-sow basil

    Thin ruthlessly once seedlings are up. Crowded roots mean smaller crops from every plant.

Coming up in June — start thinking about
  • Transplants going out: basil

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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.

Carlton County, Minnesota is in USDA Zone 4a. The average last spring frost is May 12 and the first fall frost is October 2, giving you a growing season of approximately 143 days.

At an elevation of 516 feet, Carlton County receives approximately 32.8 inches of rainfall annually with predominantly silt loam soil. Summer highs average 82°F, so choose short-season varieties of Basil to ensure they mature before fall.

Carlton County, MN (Zone 4a) Short season
143 days
Last Spring Frost May 12
143 growing days
First Fall Frost October 2

Carlton County Soil Profile

Soil Type

Silt Loam

Soil pH

6.2-7.1

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (2 days to spare)
Start indoors: Mar 10 Transplant: May 26 🍅 Harvest: Jul 21 – Sep 22
Recommended (50%) ✓ Fits season (3 days to spare)
Start indoors: Mar 17 Transplant: Jun 2 🍅 Harvest: Jul 28 – Sep 29
Safe Start (90%) ✗ May not fit
Start indoors: Apr 5 Transplant: Jun 21 🍅 Harvest: Aug 16 – Oct 18

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 Carlton County

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

Soil pH

Your soil pH (6.2–7.1) overlaps with Basil's range (6.0–7.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is excellent (4.5%) — 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 19 to harvest before frost.

Plant Water Budget

Plant needs
0.6″/week
Rainfall provides
1.0″/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 1.5" 0" ❄️ Dormant
Feb 1.5" 0" ❄️ Dormant
Mar 2.5" 0" ❄️ Dormant
Apr 3.1" 0" ❄️ Dormant
May 2.6" 3.4" 0" ✅ Rainfall sufficient
Jun 2.6" 4.1" 0" ✅ Rainfall sufficient
Jul 2.6" 3.5" 0" ✅ Rainfall sufficient
Aug 2.6" 3.4" 0" ✅ Rainfall sufficient
Sep 2.6" 2.7" 0" ✅ Rainfall sufficient
Oct 2.6" 2.8" 0" ✅ Rainfall sufficient
Nov 2.5" 0" ❄️ Dormant
Dec 1.9" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Carlton 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 ~719 GDD — county provides 1,644 GDD Excellent fit

Basil Planting Timeline — Carlton County, MN

Basil Planting Calendar

Activity When Date Range
Start Indoors March 17 Mar 17 – Mar 31
Transplant Outdoors June 2 Jun 2 – Jun 16
Direct Sow May 19 May 19 – Jun 9
Harvest July 28 Jul 28 – Sep 29

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

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors
April
May 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 Carlton County

Growing Tips for Basil in Carlton County

Direct sow Basil outdoors after May 12 in Carlton 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 Carlton County, MN?

Carlton County is in Zone 4a with an average last frost of May 12. Plan your Basil planting based on this frost date — see the calendar above for exact timing.

What planting zone is Carlton County, MN?

Carlton County, Minnesota is in USDA Hardiness Zone 4a. The average last spring frost is May 12 and first fall frost is October 2.

🌱

Your Carlton County Garden Planner — Free

A 24-page printable planner built for Carlton 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 Carlton County, MN. 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.