When to Plant Watercress in St. Mary Parish, LA
St. Mary Parish, Louisiana gardeners: here's your May plan
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in St. Mary Parish, Louisiana.
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Bring in the watercress
Taste as you pick. The first ripe produce is the best feedback loop you'll get all season.
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. Mary Parish, Louisiana is in USDA Zone 9b. The average last spring frost is February 14 and the first fall frost is December 5, giving you a growing season of approximately 294 days.
At an elevation of 252 feet, St. Mary Parish receives approximately 48.5 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 95°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.
St. Mary Parish Soil Profile
Soil Type
Sandy Loam
Soil pH
4.8-6.4
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. Mary Parish
How your county's soil matches Watercress's growing requirements.
Soil pH
Your soil pH (4.8–6.4) is more acidic than Watercress prefers (6.5–7.5). Add garden lime to raise pH.
Soil Texture
Sandy soil in St. Mary 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 (2.0%). 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 Oct 06 to harvest before frost.
For a dedicated fall crop, sow by Oct 10.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
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 | — | 3.6" | 0" | ❄️ Dormant |
| Feb | 6.5" | 3.4" | 3.1" | 💧 Light watering |
| Mar | 6.5" | 5.1" | 1.4" | 💧 Light watering |
| Apr | 6.5" | 3.8" | 2.7" | 💧 Light watering |
| May | 6.5" | 3.8" | 2.7" | 💧 Light watering |
| Jun | 6.5" | 3.6" | 2.9" | 💧 Light watering |
| Jul | 6.5" | 5.6" | 0.9" | 💧 Light watering |
| Aug | 6.5" | 5.1" | 1.4" | 💧 Light watering |
| Sep | 6.5" | 3.5" | 3" | 💧 Light watering |
| Oct | 6.5" | 3.1" | 3.4" | 🚿 Regular watering |
| Nov | 6.5" | 3.9" | 2.6" | 💧 Light watering |
| Dec | 6.5" | 4.2" | 2.3" | 💧 Light watering |
Water needs are for active growing months only (Feb–Dec in St. Mary 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. Mary Parish, LA
Watercress Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 17 | Jan 17 – Jan 31 |
| Transplant Outdoors | February 14 | Feb 14 – Feb 28 |
| Direct Sow | January 24 | Jan 24 – Feb 14 |
| Harvest | March 28 | Mar 28 – May 2 |
| Fall Sowing | October 10 | Oct 10 – Oct 24 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Direct Sow |
| February | Transplant Outdoors Direct Sow |
| March | Harvest |
| April | Harvest |
| May | Harvest |
| June | — |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1.5"/week · 1-2 times/week
📅 Days to Maturity
40–60 days
🧪 Soil pH
Needs 6.5–7.5 · Your soil: too_acidic
🗺️ USDA Zone
Zone 9b
📆 Growing Season
294 days in St. Mary Parish
Growing Tips for Watercress in St. Mary Parish
Direct sow Watercress outdoors after February 14 in St. Mary Parish when soil has warmed and frost danger has passed.
Sandy soil in St. Mary Parish dries quickly — mulch Watercress with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.
Your generous 295.0-day season in St. Mary 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. Mary Parish, LA?
St. Mary Parish is in Zone 9b with an average last frost of February 14. Plan your Watercress planting based on this frost date — see the calendar above for exact timing.
What planting zone is St. Mary Parish, LA?
St. Mary Parish, Louisiana is in USDA Hardiness Zone 9b. The average last spring frost is February 14 and first fall frost is December 5.
Your St. Mary Parish Garden Planner — Free
A 24-page printable planner built for St. Mary Parish (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.