When to Plant Watercress in Benton County, OR
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.
Benton County, Oregon is in USDA Zone 8a. The average last spring frost is April 14 and the first fall frost is October 30, giving you a growing season of approximately 199 days.
At an elevation of 97 feet, Benton County receives approximately 53.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Watercress during the growing season. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Watercress root diseases.
Benton County Soil Profile
Soil Type
Silt Loam
Soil pH
5.6-6.2
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 Benton County
How your county's soil matches Watercress's growing requirements.
Soil pH
Your soil pH (5.6–6.2) is more acidic than Watercress prefers (6.5–7.5). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Benton County is excellent for Watercress — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.7%) — Watercress will thrive.
How to Plant Watercress
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Watercress
Sow every 4.6 weeks. Last sowing by Aug 31 to harvest before frost.
For a dedicated fall crop, sow by Aug 21.
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 | — | 8.1" | 0" | ❄️ Dormant |
| Feb | — | 6.1" | 0" | ❄️ Dormant |
| Mar | — | 5.8" | 0" | ❄️ Dormant |
| Apr | 6.5" | 3.6" | 2.9" | 💧 Light watering |
| May | 6.5" | 3.3" | 3.2" | 💧 Light watering |
| Jun | 6.5" | 1.9" | 4.6" | 🚿 Regular watering |
| Jul | 6.5" | 0.9" | 5.6" | 🚿 Regular watering |
| Aug | 6.5" | 0.8" | 5.7" | 🚿 Regular watering |
| Sep | 6.5" | 2.3" | 4.2" | 🚿 Regular watering |
| Oct | 6.5" | 3.8" | 2.7" | 💧 Light watering |
| Nov | — | 8.3" | 0" | ❄️ Dormant |
| Dec | — | 8.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Benton 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 — Benton County, OR
Watercress Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 10 | Mar 10 – Mar 24 |
| Transplant Outdoors | April 14 | Apr 14 – Apr 28 |
| Direct Sow | March 31 | Mar 31 – Apr 21 |
| Harvest | May 26 | May 26 – Jun 30 |
| Fall Sowing | August 21 | Aug 21 – Sep 4 |
Plant 0.5" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | Harvest |
| June | Harvest |
| July | — |
| August | Fall Sowing |
| September | Fall Sowing |
| October | — |
| 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 8a
📆 Growing Season
199 days in Benton County
Growing Tips for Watercress in Benton County
Direct sow Watercress outdoors after April 14 in Benton County when soil has warmed and frost danger has passed.
Your generous 199.0-day season in Benton 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 Benton County, OR?
Benton County is in Zone 8a with an average last frost of April 14. Plan your Watercress planting based on this frost date — see the calendar above for exact timing.
What planting zone is Benton County, OR?
Benton County, Oregon is in USDA Hardiness Zone 8a. The average last spring frost is April 14 and first fall frost is October 30.
Plan Your Garden with Confidence
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