When to Plant Mint in Washington County, CO
May in Washington County, Colorado — your action list
A quick May briefing for Washington County, Colorado gardeners — what's urgent, what's next, and what can wait.
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Move mint from tray to bed
Bring a watering can to the bed. Each transplant gets a drink the moment it's in the ground, not ten minutes later.
Mint is a vigorous perennial herb with refreshing, aromatic leaves used in teas, cocktails, and cooking. It spreads aggressively by underground runners.
Washington County, Colorado is in USDA Zone 5b. The average last spring frost is May 10 and the first fall frost is October 5, giving you a growing season of approximately 148 days.
At an elevation of 6,091 feet, Washington County receives approximately 13 inches of rainfall annually with predominantly loam soil. Summer highs average 85°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.
Washington County Soil Profile
Soil Type
Loam
Soil pH
6.8-8.3
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 Washington County
How your county's soil matches Mint's growing requirements.
Soil pH
Your soil pH (6.8–8.3) is more alkaline than Mint prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Washington County is excellent for Mint — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.2%). Annual compost additions will help Mint.
How to Plant Mint
Succession Planting Mint
Sow every 6.9 weeks. Last sowing by Jul 07 to harvest before frost.
Plant Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
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" | 0" | ❄️ Dormant |
| Feb | — | 0.7" | 0" | ❄️ Dormant |
| Mar | — | 1" | 0" | ❄️ Dormant |
| Apr | — | 1.4" | 0" | ❄️ Dormant |
| May | 3" | 1.5" | 1.5" | 🚿 Regular watering |
| Jun | 3" | 1" | 2" | 🚿 Regular watering |
| Jul | 3" | 1.2" | 1.8" | 🚿 Regular watering |
| Aug | 3" | 1.5" | 1.5" | 🚿 Regular watering |
| Sep | 3" | 1.1" | 1.9" | 🚿 Regular watering |
| Oct | 3" | 1.1" | 1.9" | 🚿 Regular watering |
| Nov | — | 0.9" | 0" | ❄️ Dormant |
| Dec | — | 0.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Washington 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 — Washington County, CO
Mint Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 17 | May 17 – May 31 |
| Harvest | July 19 | Jul 19 – Sep 27 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| 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: too_alkaline
🗺️ USDA Zone
Zone 5b
📆 Growing Season
148 days in Washington County
Growing Tips for Mint in Washington County
Direct sow Mint outdoors after May 10 in Washington 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 Washington County, CO?
Washington County is in Zone 5b with an average last frost of May 10. Plan your Mint planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, CO?
Washington County, Colorado is in USDA Hardiness Zone 5b. The average last spring frost is May 10 and first fall frost is October 5.
Your Washington County Garden Planner — Free
A 24-page printable planner built for Washington County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.