When to Plant Mint in Umatilla County, OR
Umatilla County, Oregon gardeners: here's your May plan
Your Umatilla County, Oregon garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.
Mint is a vigorous perennial herb with refreshing, aromatic leaves used in teas, cocktails, and cooking. It spreads aggressively by underground runners.
Umatilla County, Oregon is in USDA Zone 7a. The average last spring frost is April 23 and the first fall frost is October 20, giving you a growing season of approximately 180 days.
At an elevation of 2,195 feet, Umatilla County receives approximately 14.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Mint during the growing season. With low rainfall, drip irrigation is essential for growing Mint successfully. Mulch heavily to conserve soil moisture.
Umatilla County Soil Profile
Soil Type
Silt Loam
Soil pH
5.2-6.8
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 Umatilla County
How your county's soil matches Mint's growing requirements.
Soil pH
Your soil pH (5.2–6.8) overlaps with Mint's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Umatilla County is excellent for Mint — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.1%) — Mint will thrive.
How to Plant Mint
Succession Planting Mint
Sow every 6.9 weeks. Last sowing by Jul 22 to harvest before frost.
Plant Water Budget
Monthly Watering Guide for Mint
Mint needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.
| Month | Mint Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.8" | 0" | ❄️ Dormant |
| Feb | — | 1.8" | 0" | ❄️ Dormant |
| Mar | — | 1.3" | 0" | ❄️ Dormant |
| Apr | 3" | 1.1" | 1.9" | 🚿 Regular watering |
| May | 3" | 0.9" | 2.1" | 🚿 Regular watering |
| Jun | 3" | 0.6" | 2.4" | 🚿 Regular watering |
| Jul | 3" | 0.3" | 2.7" | 🚿 Regular watering |
| Aug | 3" | 0.3" | 2.7" | 🚿 Regular watering |
| Sep | 3" | 0.6" | 2.4" | 🚿 Regular watering |
| Oct | 3" | 1.4" | 1.6" | 🚿 Regular watering |
| Nov | — | 2.4" | 0" | ❄️ Dormant |
| Dec | — | 2.1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Umatilla County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Mint 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.
Mint Planting Timeline — Umatilla County, OR
Mint Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 30 | Apr 30 – May 14 |
| Harvest | July 2 | Jul 2 – Sep 10 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | Transplant Outdoors |
| June | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
0.7"/week · 1-2 times/week
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
180 days in Umatilla County
Growing Tips for Mint in Umatilla County
Direct sow Mint outdoors after April 23 in Umatilla County when soil has warmed and frost danger has passed.
General growing tips
Always grow mint in containers or with underground barriers to control spreading. Harvest regularly to keep plants compact. Cut plants back in late summer for a fresh fall flush.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Mint in Other Locations
Frequently Asked Questions
When should I plant Mint in Umatilla County, OR?
Umatilla County is in Zone 7a with an average last frost of April 23. Plan your Mint planting based on this frost date — see the calendar above for exact timing.
What planting zone is Umatilla County, OR?
Umatilla County, Oregon is in USDA Hardiness Zone 7a. The average last spring frost is April 23 and first fall frost is October 20.
Your Umatilla County Garden Planner — Free
A 24-page printable planner built for Umatilla County (Zone 7a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.