When to Plant Watercress in Williamson County, TX
What to do 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.
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Pick watercress
The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.
Watercress is a semi-aquatic plant with a peppery, tangy flavor rich in vitamins and minerals. It grows naturally along streams and can be cultivated in containers with standing water.
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 Watercress during the growing season. Clay soil retains moisture well for Watercress, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Watercress root diseases.
Williamson County Soil Profile
Soil Type
Clay
Soil pH
7.1-7.8
Drainage
Well Drained
Plant Planting Risk Windows
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 Watercress's growing requirements.
Soil pH
Your soil pH (7.1–7.8) overlaps with Watercress's range (6.5–7.5), though not a perfect match.
Soil Texture
Heavy clay soil (46% clay) in Williamson County compacts easily and drains slowly. Amend with compost and avoid working soil when wet.
Drainage
Drainage is adequate for Watercress.
Organic Matter
Organic matter is moderate (2.6%). Annual compost additions will help Watercress.
How to Plant Watercress
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Succession Planting Watercress
Sow every 4.6 weeks. Last sowing by Sep 23 to harvest before frost.
For a dedicated fall crop, sow by Sep 27.
Plant Water Budget
Monthly Watering Guide for Watercress
Watercress needs approximately 1.5 inches of water per week (6.5" per month). Here's how your county's rainfall compares month by month.
| Month | Watercress Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 2" | 0" | ❄️ Dormant |
| Mar | 6.5" | 3.4" | 3.1" | 💧 Light watering |
| Apr | 6.5" | 6.5" | 0" | ✅ Rainfall sufficient |
| May | 6.5" | 7.7" | 0" | ✅ Rainfall sufficient |
| Jun | 6.5" | 7.6" | 0" | ✅ Rainfall sufficient |
| Jul | 6.5" | 6.6" | 0" | ✅ Rainfall sufficient |
| Aug | 6.5" | 6.1" | 0.4" | 💧 Light watering |
| Sep | 6.5" | 5.4" | 1.1" | 💧 Light watering |
| Oct | 6.5" | 3.7" | 2.8" | 💧 Light watering |
| Nov | 6.5" | 1.7" | 4.8" | 🚿 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.
Watercress 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.
Watercress Planting Timeline — Williamson County, TX
Watercress 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 | April 16 | Apr 16 – May 21 |
| Fall Sowing | September 27 | Sep 27 – Oct 11 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors Direct Sow |
| March | Transplant Outdoors Direct Sow |
| April | Harvest |
| May | Harvest |
| June | — |
| July | — |
| August | — |
| September | Fall Sowing |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1.5"/week · Only during dry spells
📅 Days to Maturity
40–60 days
🧪 Soil pH
Needs 6.5–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 9a
📆 Growing Season
262 days in Williamson County
Growing Tips for Watercress in Williamson County
Direct sow Watercress 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 Watercress. Avoid tilling when soil is wet to prevent compaction.
Your generous 262.0-day season in Williamson County allows multiple plantings of Watercress. Sow every 20.0 days for continuous harvest.
Common pests for Watercress in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Grow in containers with trays of water kept fresh. Provide partial shade and cool conditions. Harvest stems by cutting above water level. Replace water frequently to prevent stagnation.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Watercress in Other Locations
Frequently Asked Questions
When should I plant Watercress in Williamson County, TX?
Williamson County is in Zone 9a with an average last frost of March 5. Plan your Watercress 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.