When to Plant Thai Basil in USDA Zone 4b
May to-do list for Zone 4b
Each item below is timed to Zone 4b's frost dates and soil temperatures. Skip nothing, stress about nothing.
-
Sow thai basil where they'll grow
Rake a smooth bed, make a shallow furrow, drop seeds at the spacing on the packet, water gently, walk away.
Get ahead of June
- Transplants going out: 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.
In Zone 4b, the average last spring frost is around May 1 and the first fall frost is around October 3, giving you a growing season of approximately 155 days.
Thai Basil Planting Timeline — Zone 4b
Where Is USDA Zone 4b?
The map below highlights the states that contain Zone 4b. Click any state to see the Thai Basil planting schedule for that location.
Thai Basil Planting Calendar — Zone 4b
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 6 | Mar 6 – Mar 20 |
| Transplant Outdoors | May 22 | May 22 – Jun 5 |
| Direct Sow | May 8 | May 8 – May 29 |
| Harvest | July 17 | Jul 17 – Sep 18 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Free Zone 4b Planting Calendar PDF
Know exactly when to plant every crop in your zone. Get a printable month-by-month calendar customized for Zone 4b with start dates, transplant windows, and harvest times.
Growing Conditions
Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
Days to Maturity
50–75 days
Soil pH
6 – 7
Zone Temperature Range
°F to °F average annual minimum
Growing Season
155 days (Zone average)
Planting Specifications
| Planting Depth | 0.5 inches |
| Plant Spacing | 8 inches apart |
| Row Spacing | 12 inches between rows |
Succession Planting Thai Basil in Zone
Sow every 5.7 weeks for continuous harvest throughout the season.
Growing Tips for Thai Basil in Zone
Zone has a short growing season (~155 days). Start Thai Basil indoors early and use season-extension techniques like row covers and cold frames.
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
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Saving Thai Basil Seeds
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Breathable fabric pots that promote healthy root growth and prevent overwatering.
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Start seeds indoors with reusable cell trays and humidity domes.
Related Plants
Thai Basil in Other Zones
Thai Basil by State
- Alabama
- Alaska
- Arizona
- Arkansas
- California
- Colorado
- Connecticut
- Delaware
- Florida
- Georgia
- Hawaii
- Idaho
- Illinois
- Indiana
- Iowa
- Kansas
- Kentucky
- Louisiana
- Maine
- Maryland
- Massachusetts
- Michigan
- Minnesota
- Mississippi
- Missouri
- Montana
- Nebraska
- Nevada
- New Hampshire
- New Jersey
- New Mexico
- New York
- North Carolina
- North Dakota
- Ohio
- Oklahoma
- Oregon
- Pennsylvania
- Rhode Island
- South Carolina
- South Dakota
- Tennessee
- Texas
- Utah
- Vermont
- Virginia
- Washington
- West Virginia
- Wisconsin
- Wyoming
Frequently Asked Questions
When should I plant Thai Basil in Zone 4b?
In Zone 4b, plan your Thai Basil planting around the average last frost date of May 1. Start seeds indoors around March 6. Direct sow outdoors around May 8. Transplant seedlings around May 22.
Can Thai Basil grow in Zone 4b?
Yes, Thai Basil can grow well in Zone 4b, hardy in USDA zones 4a through 11b. Zone 4b has a growing season of approximately 155 days, which is sufficient for Thai Basil (50-75 days to maturity).
When can I harvest Thai Basil in Zone 4b?
In Zone 4b, expect to harvest Thai Basil from July 17 – September 18. Thai Basil takes 50-75 days from planting to harvest.
What is the last frost date for Zone 4b?
The average last spring frost in Zone 4b is around May 1, and the first fall frost is around October 3. This gives a growing season of approximately 155 days. These are 50% probability dates — actual frost dates vary year to year.
What should I plant next to Thai Basil?
Good companion plants for Thai Basil include Tomatoes, Peppers, Eggplant. These companions can help with pest control, pollination, and nutrient sharing.
Your Free Printable Garden Planner
A 24-page printable planner tailored to your zone. Planting dates, monthly task lists, harvest log, seed inventory, and succession charts — everything you need to plan a full season.