When to Plant Watercress in St. Tammany Parish, LA
May to-do list for St. Tammany Parish, Louisiana
Welcome to May in Zone 9a. These are the moves that will have the biggest impact on your growing season.
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Harvest watercress as they ripen
Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.
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.
St. Tammany Parish, Louisiana is in USDA Zone 9a. The average last spring frost is February 20 and the first fall frost is November 23, giving you a growing season of approximately 276 days.
At an elevation of 321 feet, St. Tammany Parish receives approximately 57.9 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 96°F, so Watercress may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Watercress will need more frequent watering and organic matter to retain nutrients. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Watercress root diseases.
St. Tammany Parish Soil Profile
Soil Type
Sandy Loam
Soil pH
4.8-6.1
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 St. Tammany Parish
How your county's soil matches Watercress's growing requirements.
Soil pH
Your soil pH (4.8–6.1) is more acidic than Watercress prefers (6.5–7.5). Add garden lime to raise pH.
Soil Texture
Sandy soil in St. Tammany Parish warms quickly in spring but drains fast. Watercress will need more frequent watering and regular compost additions to retain nutrients.
Drainage
Drainage is adequate for Watercress.
Organic Matter
Organic matter is moderate (2.1%). 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 24 to harvest before frost.
For a dedicated fall crop, sow by Sep 28.
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 | — | 4.5" | 0" | ❄️ Dormant |
| Feb | 6.5" | 4.5" | 2" | 💧 Light watering |
| Mar | 6.5" | 5.8" | 0.7" | 💧 Light watering |
| Apr | 6.5" | 4.2" | 2.3" | 💧 Light watering |
| May | 6.5" | 5.2" | 1.3" | 💧 Light watering |
| Jun | 6.5" | 4.6" | 1.9" | 💧 Light watering |
| Jul | 6.5" | 6.8" | 0" | ✅ Rainfall sufficient |
| Aug | 6.5" | 5.3" | 1.2" | 💧 Light watering |
| Sep | 6.5" | 4.2" | 2.3" | 💧 Light watering |
| Oct | 6.5" | 4.1" | 2.4" | 💧 Light watering |
| Nov | 6.5" | 4.3" | 2.2" | 💧 Light watering |
| Dec | — | 4.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Feb–Nov in St. Tammany Parish). 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 — St. Tammany Parish, LA
Watercress Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 23 | Jan 23 – Feb 6 |
| Transplant Outdoors | February 20 | Feb 20 – Mar 6 |
| Direct Sow | January 30 | Jan 30 – Feb 20 |
| Harvest | April 3 | Apr 3 – May 8 |
| Fall Sowing | September 28 | Sep 28 – Oct 12 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Direct Sow |
| February | Start Indoors Transplant Outdoors Direct Sow |
| March | Transplant Outdoors |
| 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: too_acidic
🗺️ USDA Zone
Zone 9a
📆 Growing Season
276 days in St. Tammany Parish
Growing Tips for Watercress in St. Tammany Parish
Direct sow Watercress outdoors after February 20 in St. Tammany Parish when soil has warmed and frost danger has passed.
Sandy soil in St. Tammany Parish dries quickly — mulch Watercress with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
With summer highs reaching 96°F in St. Tammany Parish, provide afternoon shade for Watercress and water deeply in the morning.
Your generous 277.0-day season in St. Tammany Parish 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 St. Tammany Parish, LA?
St. Tammany Parish is in Zone 9a with an average last frost of February 20. Plan your Watercress planting based on this frost date — see the calendar above for exact timing.
What planting zone is St. Tammany Parish, LA?
St. Tammany Parish, Louisiana is in USDA Hardiness Zone 9a. The average last spring frost is February 20 and first fall frost is November 23.
Your St. Tammany Parish Garden Planner — Free
A 24-page printable planner built for St. Tammany Parish (Zone 9a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.