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When to Plant Celeriac in Williamson County, TX

Williamson County, Texas Zone 9a May

Top priorities for Williamson County, Texas gardeners in May

If you only do a handful of things in the garden this May, make it these. They're sequenced around your zone's frost timing.

Avg. last frost March 5
Avg. first frost November 22
Soil temp (4") 72°F
Watering Low
Pest pressure High
Daylight 13.6 hrs
June prep starts now
  • First harvests: celeriac

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Celeriac is a celery relative grown for its knobby, flavorful root rather than its stalks. It has a rich celery flavor and is excellent roasted, mashed, or in soups.

Williamson County, Texas is in USDA Zone 9a. The average last spring frost is March 5 and the first fall frost is November 22, giving you a growing season of approximately 262 days.

At an elevation of 1,023 feet, Williamson County receives approximately 53.3 inches of rainfall annually with predominantly clay soil. Summer highs average 94°F, providing good warmth for Celeriac during the growing season. Clay soil retains moisture well for Celeriac, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Celeriac root diseases.

Williamson County, TX (Zone 9a) Long season
262 days
Last Spring Frost March 5
262 growing days
First Fall Frost November 22

Williamson County Soil Profile

Soil Type

Clay

Soil pH

7.1-7.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (124 days to spare)
Start indoors: Jan 24 Transplant: Feb 21 🍅 Harvest: Jun 6 – Jul 11
Recommended (50%) ✓ Fits season (122 days to spare)
Start indoors: Feb 5 Transplant: Mar 5 🍅 Harvest: Jun 18 – Jul 23
Safe Start (90%) ✓ Fits season (110 days to spare)
Start indoors: Mar 9 Transplant: Apr 6 🍅 Harvest: Jul 20 – Aug 24

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 Williamson County

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

Soil pH

Your soil pH (7.1–7.8) is more alkaline than Celeriac prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

Your soil has 46% clay, which can cause forked or stunted roots for Celeriac. Use raised beds with loose, sandy mix for best results.

Drainage

Drainage is adequate for Celeriac.

Organic Matter

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

How to Plant Celeriac

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Fall planting: Sow 8 weeks before your first frost date for a fall harvest.

Plant Water Budget

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

Monthly Watering Guide for Celeriac

Celeriac needs approximately 0.9 inches of water per week (3.9" per month). Here's how your county's rainfall compares month by month.

Month Celeriac Needs Rainfall You Supplement Action
Jan 1.4" 0" ❄️ Dormant
Feb 2" 0" ❄️ Dormant
Mar 3.9" 3.4" 0.5" 💧 Light watering
Apr 3.9" 6.5" 0" ✅ Rainfall sufficient
May 3.9" 7.7" 0" ✅ Rainfall sufficient
Jun 3.9" 7.6" 0" ✅ Rainfall sufficient
Jul 3.9" 6.6" 0" ✅ Rainfall sufficient
Aug 3.9" 6.1" 0" ✅ Rainfall sufficient
Sep 3.9" 5.4" 0" ✅ Rainfall sufficient
Oct 3.9" 3.7" 0.2" 💧 Light watering
Nov 3.9" 1.7" 2.2" 🚿 Regular watering
Dec 1.3" 0" ❄️ Dormant

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

Celeriac 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.

Celeriac needs ~2,255 GDD — county provides 5,371 GDD Excellent fit

Celeriac Planting Timeline — Williamson County, TX

Celeriac Planting Calendar

Activity When Date Range
Start Indoors February 5 Feb 5 – Feb 19
Transplant Outdoors March 5 Mar 5 – Mar 19
Direct Sow February 12 Feb 12 – Mar 5
Harvest June 18 Jun 18 – Jul 23
Fall Sowing September 27 Sep 27 – Oct 11

Plant 1" deep · 15" apart · Rows 24" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.9"/week · Natural rainfall sufficient

📅 Days to Maturity

100–120 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 9a

📆 Growing Season

262 days in Williamson County

Growing Tips for Celeriac in Williamson County

Direct sow Celeriac outdoors after March 05 in Williamson County when soil has warmed and frost danger has passed.

With Williamson County's clay soil (46% clay), work in 3-4 inches of compost before planting Celeriac. Avoid tilling when soil is wet to prevent compaction.

Common pests for Celeriac in this region include carrot rust fly and parsleyworm. Use row covers early in the season and inspect plants weekly.

General growing tips

Start seeds indoors 10-12 weeks before last frost. Remove side roots as they develop to encourage a single large bulb. Harvest after a light frost for best flavor.

Companion Planting

Good Companions

Avoid Planting Near

  • Carrots
  • Parsnip

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Celeriac in Williamson County, TX?

Williamson County is in Zone 9a with an average last frost of March 5. Plan your Celeriac planting based on this frost date — see the calendar above for exact timing.

What planting zone is Williamson County, TX?

Williamson County, Texas is in USDA Hardiness Zone 9a. The average last spring frost is March 5 and first fall frost is November 22.

🌱

Your Williamson County Garden Planner — Free

A 24-page printable planner built for Williamson 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 Williamson County, TX. Local conditions may vary. Last updated: May 2026.

Sources & credits

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