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When to plant Mitsuba in Delta County, CO

The best window to plant Mitsuba in Delta County, is April 17–May 8, when soil warms to 50°F. Last frost typically hits May 1; first frost October 8. A second sowing from July 30 to August 13 extends the harvest into fall.

When to Plant Mitsuba in Delta County, CO

Delta County, Colorado Zone 6b August

Your August game plan for Delta County, Colorado

We've pulled the most time-sensitive tasks for Delta County, Colorado this August and put them front and centre. Tackle them in order.

Avg. last frost May 1
Avg. first frost October 8
Soil temp (4") 70°F
Watering High
Pest pressure High
Daylight 13.5 hrs
  1. Harvest mitsuba as they ripen

    The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.

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Mitsuba (Japanese parsley) is a shade-loving herb with trefoil leaves and a mild celery-parsley flavor. It is essential in Japanese cuisine for soups, salads, and garnishes.

Delta County, Colorado is in USDA Zone 6b. The average last spring frost is May 1 and the first fall frost is October 8, giving you a growing season of approximately 160 days.

At an elevation of 4,470 feet, Delta County receives approximately 13.4 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Mitsuba during the growing season. With low rainfall, drip irrigation is essential for growing Mitsuba successfully. Mulch heavily to conserve soil moisture.

Delta County, CO (Zone 6b) Moderate season
160 days
Last Spring Frost May 1
160 growing days
First Fall Frost October 8

Delta County Soil Profile

Soil Type

Loam

Soil pH

6.7-7.8

Drainage

Well Drained

Mitsuba Planting Risk Windows

Early Start (70% safe) ✓ Fits season (60 days to spare)
Start indoors: Mar 18 Transplant: Apr 15 🍅 Harvest: Jun 10 – Aug 5
Recommended (50%) ✓ Fits season (55 days to spare)
Start indoors: Mar 27 Transplant: Apr 24 🍅 Harvest: Jun 19 – Aug 14
Safe Start (90%) ✓ Fits season (56 days to spare)
Start indoors: Apr 12 Transplant: May 10 🍅 Harvest: Jul 5 – Aug 30

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 Delta County

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

Soil pH

Your soil pH (6.7–7.8) is more alkaline than Mitsuba prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.2%). Annual compost additions will help Mitsuba.

How to Plant Mitsuba

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

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Succession Planting Mitsuba

3
successive plantings in your 160-day season

Sow every 5.7 weeks. Last sowing by Jul 30 to harvest before frost.

For a dedicated fall crop, sow by Jul 30.

Mitsuba Water Budget

Plant needs
1.0″/week
Rainfall provides
0.4″/week
You supply
0.8″/week
Watering frequency 2-3 times/week
Season total 1,108 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Mitsuba

Mitsuba needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Mitsuba Needs Rainfall You Supplement Action
Jan 1" 0" ❄️ Dormant
Feb 0.7" 0" ❄️ Dormant
Mar 1.2" 0" ❄️ Dormant
Apr 1.4" 0" ❄️ Dormant
May 4.3" 1.4" 2.9" 🚿 Regular watering
Jun 4.3" 0.9" 3.4" 🚿 Regular watering
Jul 4.3" 1.3" 3" 🚿 Regular watering
Aug 4.3" 1.4" 2.9" 🚿 Regular watering
Sep 4.3" 1.1" 3.2" 🚿 Regular watering
Oct 4.3" 1.1" 3.2" 🚿 Regular watering
Nov 1.1" 0" ❄️ Dormant
Dec 0.8" 0" ❄️ Dormant

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

Mitsuba 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.

Mitsuba needs ~915 GDD — county provides 2,440 GDD Excellent fit

Mitsuba Planting Timeline — Delta County, CO

Mitsuba Planting Calendar

Activity When Date Range
Start Indoors March 27 Mar 27 – Apr 10
Transplant Outdoors April 24 Apr 24 – May 8
Direct Sow April 17 Apr 17 – May 8
Harvest June 19 Jun 19 – Aug 14
Fall Sowing July 30 Jul 30 – Aug 13

Plant 0.5" deep · 8" apart · Rows 12" apart

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors
April Start Indoors Transplant Outdoors Direct Sow
May Transplant Outdoors Direct Sow
June Harvest
July Fall Sowing Harvest
August Fall Sowing Harvest
September
October
November
December

Growing Conditions

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

1"/week · 2-3 times/week

📅 Days to Maturity

50–70 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 6b

📆 Growing Season

160 days in Delta County

Growing Tips for Mitsuba in Delta County

Direct sow Mitsuba outdoors after May 01 in Delta County when soil has warmed and frost danger has passed.

Common pests for Mitsuba in this region include carrot rust fly and parsleyworm. Use row covers early in the season and inspect plants weekly.

Delta County receives only 13" of rain annually. Mitsuba needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Direct sow or start indoors in partial shade. Mitsuba prefers cool, moist conditions. Harvest outer stems as needed. Self-sows readily in shaded garden areas.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Mitsuba in Delta County, CO?

Delta County is in Zone 6b with an average last frost of May 1. Plan your Mitsuba planting based on this frost date — see the calendar above for exact timing.

What planting zone is Delta County, CO?

Delta County, Colorado is in USDA Hardiness Zone 6b. The average last spring frost is May 1 and first fall frost is October 8.

When should I plant Mitsuba in Delta County, CO?

In Delta County, CO, plant Mitsuba after the last frost (around May 1) and before the first frost (around October 8). Best results when soil holds above 50°F.

What growing zone is Delta County, CO for Mitsuba?

Delta County sits in USDA Zone 6b. Mitsuba grows reliably in zones 4a through 9b, so it's a good fit here.

Can Mitsuba grow in Delta County's climate?

Yes — Mitsuba grows well in Delta County's temperate climate. Delta County averages a 160-day frost-free season, with last frost around May 1 and first frost around October 8.

🌱

Your Delta County Garden Planner — Free

A 22-page printable planner built for Delta County (Zone 6b). 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 Delta County, CO. Local conditions may vary. Last updated: August 2026.

Sources & credits

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