Blog

When to Plant Thai Basil in St. Bernard Parish, LA

St. Bernard Parish, Louisiana Zone 9b May

What to do in May

Each item below is timed to St. Bernard Parish, Louisiana's frost dates and soil temperatures. Skip nothing, stress about nothing.

Avg. last frost February 2
Avg. first frost December 11
Soil temp (4") 78°F
Watering Low
Pest pressure High
Daylight 13.5 hrs
  1. Start harvesting thai basil

    This is the payoff month. Bring a basket, bring a friend, and get into the beds.

A few tasks this May that'll pay off in June
  • First harvests: thai basil

Instant PDF download. No spam, unsubscribe any time.

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.

St. Bernard Parish, Louisiana is in USDA Zone 9b. The average last spring frost is February 2 and the first fall frost is December 11, giving you a growing season of approximately 312 days.

At an elevation of 455 feet, St. Bernard Parish receives approximately 51.7 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 104°F, so Thai Basil may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Thai Basil will need more frequent watering and organic matter to retain nutrients. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Thai Basil root diseases.

St. Bernard Parish, LA (Zone 9b) Year-round
312 days
Last Spring Frost February 2
312 growing days
First Fall Frost December 11
Share this guide:

St. Bernard Parish Soil Profile

Soil Type

Sandy Loam

Soil pH

5.2-6.5

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (192 days to spare)
Start indoors: Dec 11 Transplant: Jan 29 🍅 Harvest: Mar 26 – May 28
Recommended (50%) ✓ Fits season (186 days to spare)
Start indoors: Dec 22 Transplant: Feb 9 🍅 Harvest: Apr 6 – Jun 8
Safe Start (90%) ✓ Fits season (169 days to spare)
Start indoors: Jan 22 Transplant: Mar 12 🍅 Harvest: May 7 – Jul 9

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 St. Bernard Parish

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

Soil pH

Your soil pH (5.2–6.5) is more acidic than Thai Basil prefers (6.0–7.0). Add garden lime to raise pH.

Soil Texture

Sandy soil in St. Bernard Parish warms quickly in spring but drains fast. Thai Basil will need more frequent watering and regular compost additions to retain nutrients.

Drainage

Drainage is adequate for Thai Basil.

Organic Matter

Organic matter is moderate (2.0%). Annual compost additions will help Thai Basil.

How to Plant Thai Basil

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

Succession Planting Thai Basil

7
successive plantings in your 312-day season

Sow every 5.7 weeks. Last sowing by Sep 27 to harvest before frost.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.7″/week
You supply
0.0″/week
Watering frequency Only during dry spells
Season total 17 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 4.6" 0" ❄️ Dormant
Feb 4.3" 4.4" 0" ✅ Rainfall sufficient
Mar 4.3" 5.3" 0" ✅ Rainfall sufficient
Apr 4.3" 4" 0.3" 💧 Light watering
May 4.3" 4.4" 0" ✅ Rainfall sufficient
Jun 4.3" 4.8" 0" ✅ Rainfall sufficient
Jul 4.3" 5.9" 0" ✅ Rainfall sufficient
Aug 4.3" 4.2" 0.1" 💧 Light watering
Sep 4.3" 3.6" 0.7" 💧 Light watering
Oct 4.3" 3.1" 1.2" 💧 Light watering
Nov 4.3" 3.9" 0.4" 💧 Light watering
Dec 4.3" 3.5" 0.8" 💧 Light watering

Water needs are for active growing months only (Feb–Dec in St. Bernard Parish). 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 ~1,750 GDD — county provides 8,764 GDD Excellent fit

Thai Basil Planting Timeline — St. Bernard Parish, LA

Thai Basil Planting Calendar

Activity When Date Range
Start Indoors December 22 Dec 22 – Jan 5
Transplant Outdoors February 9 Feb 9 – Feb 23
Direct Sow February 9 Feb 9 – Mar 2
Harvest April 6 Apr 6 – Jun 8

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

Month-by-Month Timeline

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

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: too_acidic

🗺️ USDA Zone

Zone 9b

📆 Growing Season

312 days in St. Bernard Parish

Growing Tips for Thai Basil in St. Bernard Parish

Direct sow Thai Basil outdoors after February 02 in St. Bernard Parish when soil has warmed and frost danger has passed.

Sandy soil in St. Bernard Parish dries quickly — mulch Thai Basil with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.

With summer highs reaching 104°F in St. Bernard Parish, provide afternoon shade for Thai Basil and water deeply in the morning.

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 St. Bernard Parish, LA?

St. Bernard Parish is in Zone 9b with an average last frost of February 2. Plan your Thai Basil planting based on this frost date — see the calendar above for exact timing.

What planting zone is St. Bernard Parish, LA?

St. Bernard Parish, Louisiana is in USDA Hardiness Zone 9b. The average last spring frost is February 2 and first fall frost is December 11.

🌱

Your St. Bernard Parish Garden Planner — Free

A 24-page printable planner built for St. Bernard Parish (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

Instant PDF download. No spam, unsubscribe any time.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for St. Bernard Parish, LA. 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.