When to plant Thai Basil in Marshall County County,
The best window to plant Thai Basil in Marshall County County, is April 28–May 19, when soil warms to 50°F. Last frost typically hits April 21; first frost October 13.
When to Plant Thai Basil in Marshall County, IL
Marshall County, Illinois gardeners: here's your June plan
Here's what deserves your attention in Marshall County, Illinois this month. Everything below is tailored to Zone 5b and timed around your local frost dates.
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Fire up the seed-starting tray: thai basil
Starting these indoors now means sturdy transplants ready the moment your soil warms up.
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Start harvesting thai basil
Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.
To set up a strong July, finish these tasks
- First harvests: thai basil
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.
Marshall County, Illinois is in USDA Zone 5b. The average last spring frost is April 21 and the first fall frost is October 13, giving you a growing season of approximately 175 days.
At an elevation of 1,177 feet, Marshall County receives approximately 30.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Thai Basil to ensure they mature before fall.
Marshall County Soil Profile
Soil Type
Silt Loam
Soil pH
6-6.8
Drainage
Well Drained
Thai Basil Planting Risk Windows
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 Marshall County
How your county's soil matches Thai Basil's growing requirements.
Soil pH
Your soil pH (6.0–6.8) is within Thai Basil's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in Marshall County is excellent for Thai Basil — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.2%) — Thai Basil will thrive.
How to Plant Thai Basil
Succession Planting Thai Basil
Sow every 5.7 weeks. Last sowing by Jul 30 to harvest before frost.
Thai Basil Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
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 | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 1.3" | 0" | ❄️ Dormant |
| Mar | — | 2.3" | 0" | ❄️ Dormant |
| Apr | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| May | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Jun | 4.3" | 4" | 0.3" | 💧 Light watering |
| Jul | 4.3" | 3" | 1.3" | 💧 Light watering |
| Aug | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Sep | 4.3" | 2.7" | 1.6" | 💧 Light watering |
| Oct | 4.3" | 2.5" | 1.8" | 💧 Light watering |
| Nov | — | 2" | 0" | ❄️ Dormant |
| Dec | — | 1.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Marshall 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 Planting Timeline — Marshall County, IL
Thai Basil Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 3 | Mar 3 – Mar 17 |
| Transplant Outdoors | May 5 | May 5 – May 19 |
| Direct Sow | April 28 | Apr 28 – May 19 |
| Harvest | June 30 | Jun 30 – Sep 1 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 1-2 times/week
📅 Days to Maturity
50–75 days
🧪 Soil pH
Needs 6–7 · Your soil: ideal
🗺️ USDA Zone
Zone 5b
📆 Growing Season
175 days in Marshall County
Growing Tips for Thai Basil in Marshall County
Direct sow Thai Basil outdoors after April 21 in Marshall 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
Check more plant combinations with our Companion Planting Checker →
Thai Basil in Other Locations
Frequently Asked Questions
When should I plant Thai Basil in Marshall County, IL?
Marshall County is in Zone 5b with an average last frost of April 21. Plan your Thai Basil planting based on this frost date — see the calendar above for exact timing.
What planting zone is Marshall County, IL?
Marshall County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 21 and first fall frost is October 13.
When should I plant Thai Basil in Marshall County County, ?
In Marshall County County, , plant Thai Basil after the last frost (around April 21) and before the first frost (around October 13). Best results when soil holds above 50°F.
What growing zone is Marshall County County, for Thai Basil?
Marshall County County sits in USDA Zone 5b. Thai Basil grows reliably in zones 4a through 11b, so it's a good fit here.
Can Thai Basil grow in Marshall County County's climate?
Yes — Thai Basil grows well in Marshall County County's temperate climate. Marshall County County averages a 175-day frost-free season, with last frost around April 21 and first frost around October 13.
Your Marshall County Garden Planner — Free
A 22-page printable planner built for Marshall County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.