When to Plant Potatoes in Washington County, OR
Potatoes are a versatile staple crop that produces tubers underground. They come in hundreds of varieties with varying colors, textures, and maturity dates.
Washington County, Oregon is in USDA Zone 8b. The average last spring frost is April 15 and the first fall frost is October 27, giving you a growing season of approximately 195 days.
At an elevation of 352 feet, Washington County receives approximately 47.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Potatoes during the growing season.
Washington County Soil Profile
Soil Type
Silt Loam
Soil pH
5.8-6.4
Drainage
Well Drained
How Much Potatoes to Grow
For a family of 4, plant approximately 20 potatoes plants in about 40 sq ft. In Washington County's 195-day season, you'll have plenty of time for a full harvest. Plan your garden layout →
Monthly Watering Guide for Potatoes
Potatoes needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Potatoes Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 7.4" | 0" | ❄️ Dormant |
| Feb | — | 5.7" | 0" | ❄️ Dormant |
| Mar | — | 4.2" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3" | 1.3" | 💧 Light watering |
| May | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| Jun | 4.3" | 1.7" | 2.6" | 🚿 Regular watering |
| Jul | 4.3" | 0.6" | 3.7" | 🚿 Regular watering |
| Aug | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Sep | 4.3" | 1.9" | 2.4" | 🚿 Regular watering |
| Oct | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Nov | — | 7.3" | 0" | ❄️ Dormant |
| Dec | — | 8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Washington County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Potatoes Planting Timeline — Washington County, OR
Potatoes Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 25 | Feb 25 – Mar 11 |
| Transplant Outdoors | April 29 | Apr 29 – May 13 |
| Direct Sow | April 22 | Apr 22 – May 13 |
| Harvest | July 8 | Jul 8 – Sep 16 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
70–120 days
🧪 Soil pH
Needs 5–6.5 · Your soil: N/A
🗺️ USDA Zone
Zone 8b
📆 Growing Season
195 days in Washington County
Growing Tips for Washington County
Plant seed potatoes (not grocery store potatoes) 4 inches deep in spring. Hill soil around stems as plants grow to prevent greening. Stop watering when plants die back.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Potatoes in Other Locations
Frequently Asked Questions
When should I plant Potatoes in Washington County, OR?
Washington County is in Zone 8b with an average last frost of April 15. Plan your Potatoes planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, OR?
Washington County, Oregon is in USDA Hardiness Zone 8b. The average last spring frost is April 15 and first fall frost is October 27.
Your Washington County Garden Planner — Free
A 22-page printable planner built for Washington County (Zone 8b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.