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When to plant Thai Basil in Adams County County,

Spring Thai Basil in Adams County County goes in April 21–May 12, once nighttime temps stop dipping near freezing.

When to Plant Thai Basil in Adams County, IL

Adams County, Illinois Zone 6a June

June to-do list for Adams County, Illinois

A quick June briefing for Adams County, Illinois gardeners — what's urgent, what's next, and what can wait.

Avg. last frost April 14
Avg. first frost October 20
Soil temp (4") 69°F
Watering Low
Pest pressure High
Daylight 14.8 hrs
  1. Get thai basil seeds going inside

    Give them 6–8 weeks indoors before the last frost and you'll transplant into warm soil with seedlings that are already leaping.

  2. Collect thai basil at their peak

    Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.

Before July arrives, get these ready
  • First harvests: thai basil

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Thai basil has a distinctive anise-licorice flavor with sturdy purple stems and small leaves. It is essential in Thai, Vietnamese, and other Southeast Asian cuisines.

Adams County, Illinois is in USDA Zone 6a. The average last spring frost is April 14 and the first fall frost is October 20, giving you a growing season of approximately 189 days.

At an elevation of 1,390 feet, Adams County receives approximately 33.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Thai Basil during the growing season.

Adams County, IL (Zone 6a) Moderate season
189 days
Last Spring Frost April 14
189 growing days
First Fall Frost October 20

Adams County Soil Profile

Soil Type

Silt Loam

Soil pH

6.2-7.3

Drainage

Well Drained

Thai Basil Planting Risk Windows

Early Start (70% safe) ✓ Fits season (53 days to spare)
Start indoors: Feb 19 Transplant: Apr 23 🍅 Harvest: Jun 18 – Aug 20
Recommended (50%) ✓ Fits season (56 days to spare)
Start indoors: Feb 24 Transplant: Apr 28 🍅 Harvest: Jun 23 – Aug 25
Safe Start (90%) ✓ Fits season (54 days to spare)
Start indoors: Mar 10 Transplant: May 12 🍅 Harvest: Jul 7 – Sep 8

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 Adams County

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

Soil pH

Your soil pH (6.2–7.3) overlaps with Thai Basil's range (6.0–7.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is excellent (5.0%) — Thai Basil will thrive.

How to Plant Thai Basil

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

Succession Planting Thai Basil

4
successive plantings in your 189-day season

Sow every 5.7 weeks. Last sowing by Aug 06 to harvest before frost.

Thai Basil Water Budget

Plant needs
1.0″/week
Rainfall provides
0.7″/week
You supply
0.3″/week
Watering frequency Only during dry spells
Season total 445 gal / 100 sq ft

Monthly Watering Guide for Thai Basil

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

Month Thai Basil Needs Rainfall You Supplement Action
Jan 1.5" 0" ❄️ Dormant
Feb 1.3" 0" ❄️ Dormant
Mar 2.1" 0" ❄️ Dormant
Apr 4.3" 3" 1.3" 💧 Light watering
May 4.3" 4" 0.3" 💧 Light watering
Jun 4.3" 4.5" 0" ✅ Rainfall sufficient
Jul 4.3" 3.7" 0.6" 💧 Light watering
Aug 4.3" 3.5" 0.8" 💧 Light watering
Sep 4.3" 3.1" 1.2" 💧 Light watering
Oct 4.3" 2.5" 1.8" 💧 Light watering
Nov 2.3" 0" ❄️ Dormant
Dec 1.6" 0" ❄️ Dormant

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

Thai 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.

Thai Basil needs ~859 GDD — county provides 2,598 GDD Excellent fit

Thai Basil Planting Timeline — Adams County, IL

Thai Basil Planting Calendar

Activity When Date Range
Start Indoors February 24 Feb 24 – Mar 10
Transplant Outdoors April 28 Apr 28 – May 12
Direct Sow April 21 Apr 21 – May 12
Harvest June 23 Jun 23 – Aug 25

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Only during dry spells

📅 Days to Maturity

50–75 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 6a

📆 Growing Season

189 days in Adams County

Growing Tips for Thai Basil in Adams County

Direct sow Thai Basil outdoors after April 14 in Adams County when soil has warmed and frost danger has passed.

General growing tips

Start seeds indoors or direct sow after last frost. Thai basil holds up better to heat in cooking than sweet basil. Pinch flowers to prolong leaf production.

Companion Planting

Good Companions

Avoid Planting Near

  • Rue
  • Sage

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Thai Basil in Adams County, IL?

Adams County is in Zone 6a with an average last frost of April 14. Plan your Thai Basil planting based on this frost date — see the calendar above for exact timing.

What planting zone is Adams County, IL?

Adams County, Illinois is in USDA Hardiness Zone 6a. The average last spring frost is April 14 and first fall frost is October 20.

When should I plant Thai Basil in Adams County, ?

In Adams County, , plant Thai Basil after the last frost (around April 14) and before the first frost (around October 20). Best results when soil holds above 50°F.

What growing zone is Adams County, for Thai Basil?

Adams County sits in USDA Zone 6a. Thai Basil grows reliably in zones 4a through 11b, so it's a good fit here.

Can Thai Basil grow in Adams County's climate?

Yes — Thai Basil grows well in Adams County's temperate climate. Adams County averages a 189-day frost-free season, with last frost around April 14 and first frost around October 20.

🌱

Your Adams County Garden Planner — Free

A 22-page printable planner built for Adams County (Zone 6a). 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 Adams County, IL. Local conditions may vary. Last updated: June 2026.

Sources & credits

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