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When to Plant Oregano in Arapahoe County, CO

Arapahoe County, Colorado Zone 6a May

This month in Arapahoe County, Colorado

Your Arapahoe County, Colorado garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.

Avg. last frost May 10
Avg. first frost October 7
Soil temp (4") 37°F
Watering High
Pest pressure Low
Daylight 14.2 hrs
  1. Move oregano from tray to bed

    Water the tray well an hour before you transplant. Roots slide out cleanly and settle in faster.

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Oregano is a robust perennial herb essential to Italian and Greek cuisine. Its pungent, savory leaves intensify in flavor when dried.

Arapahoe County, Colorado is in USDA Zone 6a. The average last spring frost is May 10 and the first fall frost is October 7, giving you a growing season of approximately 150 days.

At an elevation of 7,205 feet, Arapahoe County receives approximately 21.4 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Oregano during the growing season.

Arapahoe County, CO (Zone 6a) Moderate season
150 days
Last Spring Frost May 10
150 growing days
First Fall Frost October 7
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Arapahoe County Soil Profile

Soil Type

Loam

Soil pH

6.2-8.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (11 days to spare)
Transplant: May 8 🍅 Harvest: Jul 10 – Sep 18
Recommended (50%) ✓ Fits season (10 days to spare)
Transplant: May 17 🍅 Harvest: Jul 19 – Sep 27
Safe Start (90%) ✓ Fits season (9 days to spare)
Transplant: May 29 🍅 Harvest: Jul 31 – Oct 9

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 Arapahoe County

How your county's soil matches Oregano's growing requirements.

Soil pH

Your soil pH (6.2–8.3) overlaps with Oregano's range (6.0–8.0), though not a perfect match.

Soil Texture

The loam soil in Arapahoe County is excellent for Oregano — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.5%). Annual compost additions will help Oregano.

How to Plant Oregano

0.5"
Planting Depth
8"
Between Plants
12"
Between Rows

Succession Planting Oregano

2
successive plantings in your 150-day season

Sow every 6.9 weeks. Last sowing by Jul 09 to harvest before frost.

Plant Water Budget

Plant needs
0.3″/week
Rainfall provides
0.6″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Oregano

Oregano needs approximately 0.3 inches of water per week (1.3" per month). Here's how your county's rainfall compares month by month.

Month Oregano Needs Rainfall You Supplement Action
Jan 1.3" 0" ❄️ Dormant
Feb 1.2" 0" ❄️ Dormant
Mar 1.8" 0" ❄️ Dormant
Apr 2.2" 0" ❄️ Dormant
May 1.3" 2.5" 0" ✅ Rainfall sufficient
Jun 1.3" 1.4" 0" ✅ Rainfall sufficient
Jul 1.3" 2" 0" ✅ Rainfall sufficient
Aug 1.3" 2.4" 0" ✅ Rainfall sufficient
Sep 1.3" 1.9" 0" ✅ Rainfall sufficient
Oct 1.3" 1.7" 0" ✅ Rainfall sufficient
Nov 1.5" 0" ❄️ Dormant
Dec 1.3" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Arapahoe County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Oregano 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.

Oregano needs ~1,144 GDD — county provides 2,287 GDD Excellent fit

Oregano Planting Timeline — Arapahoe County, CO

Oregano 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

MonthActivities
January
February
March
April
May Transplant Outdoors
June
July Harvest
August Harvest
September Harvest
October
November
December
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Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.3"/week · Natural rainfall sufficient

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 6–8 · Your soil: acceptable

🗺️ USDA Zone

Zone 6a

📆 Growing Season

150 days in Arapahoe County

Growing Tips for Oregano in Arapahoe County

Direct sow Oregano outdoors after May 10 in Arapahoe County when soil has warmed and frost danger has passed.

General growing tips

Start from seed, cuttings, or divisions. Harvest just before flowering for strongest flavor. Cut plants back to a few inches in spring to encourage vigorous new growth.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Oregano in Arapahoe County, CO?

Arapahoe County is in Zone 6a with an average last frost of May 10. Plan your Oregano planting based on this frost date — see the calendar above for exact timing.

What planting zone is Arapahoe County, CO?

Arapahoe County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is May 10 and first fall frost is October 7.

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Your Arapahoe County Garden Planner — Free

A 24-page printable planner built for Arapahoe County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Arapahoe County, CO. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.