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When to Plant Basil in Washington County, TX

Washington County, Texas Zone 9a May

What to do in May

A quick May briefing for Washington County, Texas gardeners — what's urgent, what's next, and what can wait.

Avg. last frost March 2
Avg. first frost November 27
Soil temp (4") 71°F
Watering Low
Pest pressure High
Daylight 13.5 hrs
  1. Bring in the basil

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

Coming up in June — start thinking about
  • First harvests: basil

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Basil is a fragrant warm-season herb essential to Italian and Thai cuisines. It comes in many varieties including sweet, Thai, purple, and lemon types.

Washington County, Texas is in USDA Zone 9a. The average last spring frost is March 2 and the first fall frost is November 27, giving you a growing season of approximately 270 days.

At an elevation of 386 feet, Washington County receives approximately 58.9 inches of rainfall annually with predominantly clay soil. Summer highs average 90°F, providing good warmth for Basil during the growing season. Clay soil retains moisture well for Basil, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Basil root diseases.

Washington County, TX (Zone 9a) Year-round
270 days
Last Spring Frost March 2
270 growing days
First Fall Frost November 27
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Washington County Soil Profile

Soil Type

Clay

Soil pH

6.9-8.4

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (147 days to spare)
Start indoors: Jan 4 Transplant: Feb 22 🍅 Harvest: Apr 19 – Jun 21
Recommended (50%) ✓ Fits season (144 days to spare)
Start indoors: Jan 19 Transplant: Mar 9 🍅 Harvest: May 4 – Jul 6
Safe Start (90%) ✓ Fits season (145 days to spare)
Start indoors: Feb 8 Transplant: Mar 29 🍅 Harvest: May 24 – Jul 26

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 Washington County

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

Soil pH

Your soil pH (6.9–8.4) is more alkaline than Basil prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

Your clay soil in Washington County is workable for Basil. Add compost annually to improve structure.

Organic Matter

Organic matter is moderate (2.6%). Annual compost additions will help Basil.

How to Plant Basil

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

Succession Planting Basil

6
successive plantings in your 270-day season

Sow every 5.7 weeks. Last sowing by Sep 13 to harvest before frost.

Plant Water Budget

Plant needs
0.6″/week
Rainfall provides
0.9″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft

Monthly Watering Guide for Basil

Basil needs approximately 0.6 inches of water per week (2.6" per month). Here's how your county's rainfall compares month by month.

Month Basil Needs Rainfall You Supplement Action
Jan 1.6" 0" ❄️ Dormant
Feb 1.9" 0" ❄️ Dormant
Mar 2.6" 4.3" 0" ✅ Rainfall sufficient
Apr 2.6" 5.8" 0" ✅ Rainfall sufficient
May 2.6" 8.3" 0" ✅ Rainfall sufficient
Jun 2.6" 9.9" 0" ✅ Rainfall sufficient
Jul 2.6" 7" 0" ✅ Rainfall sufficient
Aug 2.6" 7.4" 0" ✅ Rainfall sufficient
Sep 2.6" 5.2" 0" ✅ Rainfall sufficient
Oct 2.6" 4.2" 0" ✅ Rainfall sufficient
Nov 2.6" 2" 0.6" 💧 Light watering
Dec 1.4" 0" ❄️ Dormant

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

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.

Basil needs ~1,094 GDD — county provides 4,725 GDD Excellent fit

Basil Planting Timeline — Washington County, TX

Basil Planting Calendar

Activity When Date Range
Start Indoors January 19 Jan 19 – Feb 2
Transplant Outdoors March 9 Mar 9 – Mar 23
Direct Sow March 9 Mar 9 – Mar 30
Harvest May 4 May 4 – Jul 6

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

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.6"/week · Natural rainfall sufficient

📅 Days to Maturity

50–75 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 9a

📆 Growing Season

270 days in Washington County

Growing Tips for Basil in Washington County

Direct sow Basil outdoors after March 02 in Washington County when soil has warmed and frost danger has passed.

With Washington County's clay soil (37% clay), work in 3-4 inches of compost before planting Basil. Avoid tilling when soil is wet to prevent compaction.

General growing tips

Start seeds indoors or direct sow after last frost. Pinch flower buds to extend leaf production. Harvest leaves from the top down, cutting just above a leaf pair.

Recommended Basil Varieties for Washington County

Downy mildew-resistant basil for your humid climate

Prospera (DM-resistant) Amazel Eleonora

Companion Planting

Good Companions

Avoid Planting Near

  • Rue
  • Sage

Check more plant combinations with our Companion Planting Checker →

🌾 Save Your Own Basil Seeds
Life Cycle Annual
Pollination Self-Pollinating
How to Collect Let flower spikes dry brown on the plant.
Storage Store airtight; viable 5 years at 35°F, under 45% humidity.

Isolate 150 ft between varieties. Different basil species can cross.

Frequently Asked Questions

When should I plant Basil in Washington County, TX?

Washington County is in Zone 9a with an average last frost of March 2. Plan your Basil planting based on this frost date — see the calendar above for exact timing.

What planting zone is Washington County, TX?

Washington County, Texas is in USDA Hardiness Zone 9a. The average last spring frost is March 2 and first fall frost is November 27.

🌱

Your Washington County Garden Planner — Free

A 24-page printable planner built for Washington County (Zone 9a). 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 Washington 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.