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When to Plant Thai Basil in San Patricio County, TX

San Patricio County, Texas Zone 9b May

This month in San Patricio County, Texas

We've pulled the most time-sensitive tasks for San Patricio County, Texas this May and put them front and centre. Tackle them in order.

Avg. last frost February 12
Avg. first frost December 9
Soil temp (4") 73°F
Watering Low
Pest pressure High
Daylight 13.4 hrs
  1. Basket week: thai basil

    Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.

June will be here before you know it — start on
  • 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.

San Patricio County, Texas is in USDA Zone 9b. The average last spring frost is February 12 and the first fall frost is December 9, giving you a growing season of approximately 300 days.

At an elevation of 2,449 feet, San Patricio County receives approximately 54.7 inches of rainfall annually with predominantly loam soil. Summer highs average 100°F, so Thai Basil may need afternoon shade and extra watering during peak heat. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Thai Basil root diseases.

San Patricio County, TX (Zone 9b) Year-round
300 days
Last Spring Frost February 12
300 growing days
First Fall Frost December 9
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San Patricio County Soil Profile

Soil Type

Loam

Soil pH

6.8-7.2

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (189 days to spare)
Start indoors: Dec 9 Transplant: Jan 27 🍅 Harvest: Mar 24 – May 26
Recommended (50%) ✓ Fits season (174 days to spare)
Start indoors: Jan 1 Transplant: Feb 19 🍅 Harvest: Apr 16 – Jun 18
Safe Start (90%) ✓ Fits season (161 days to spare)
Start indoors: Jan 27 Transplant: Mar 17 🍅 Harvest: May 12 – Jul 14

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 San Patricio County

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

Soil pH

Your soil pH (6.8–7.2) overlaps with Thai Basil's range (6.0–7.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is low (1.9%). Add 2-3 inches of compost before planting 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 300-day season

Sow every 5.7 weeks. Last sowing by Sep 25 to harvest before frost.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.8″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 634 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 4.3" 1.7" 2.6" 🚿 Regular watering
Mar 4.3" 3.8" 0.5" 💧 Light watering
Apr 4.3" 6.4" 0" ✅ Rainfall sufficient
May 4.3" 8.5" 0" ✅ Rainfall sufficient
Jun 4.3" 8.1" 0" ✅ Rainfall sufficient
Jul 4.3" 7.5" 0" ✅ Rainfall sufficient
Aug 4.3" 5.6" 0" ✅ Rainfall sufficient
Sep 4.3" 5" 0" ✅ Rainfall sufficient
Oct 4.3" 3.1" 1.2" 💧 Light watering
Nov 4.3" 2" 2.3" 🚿 Regular watering
Dec 4.3" 1.4" 2.9" 🚿 Regular watering

Water needs are for active growing months only (Feb–Dec in San Patricio 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 ~1,562 GDD — county provides 7,525 GDD Excellent fit

Thai Basil Planting Timeline — San Patricio County, TX

Thai Basil Planting Calendar

Activity When Date Range
Start Indoors January 1 Jan 1 – Jan 15
Transplant Outdoors February 19 Feb 19 – Mar 5
Direct Sow February 19 Feb 19 – Mar 12
Harvest April 16 Apr 16 – Jun 18

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

Month-by-Month Timeline

MonthActivities
January Start Indoors
February Transplant Outdoors Direct Sow
March Transplant Outdoors Direct Sow
April Harvest
May Harvest
June Harvest
July
August
September
October
November
December
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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 9b

📆 Growing Season

300 days in San Patricio County

Growing Tips for Thai Basil in San Patricio County

Direct sow Thai Basil outdoors after February 12 in San Patricio County when soil has warmed and frost danger has passed.

With summer highs reaching 100°F in San Patricio County, 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 San Patricio County, TX?

San Patricio County is in Zone 9b with an average last frost of February 12. Plan your Thai Basil planting based on this frost date — see the calendar above for exact timing.

What planting zone is San Patricio County, TX?

San Patricio County, Texas is in USDA Hardiness Zone 9b. The average last spring frost is February 12 and first fall frost is December 9.

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Your San Patricio County Garden Planner — Free

A 24-page printable planner built for San Patricio County (Zone 9b). 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 San Patricio County, TX. 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.