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When to Plant Mitsuba in Lewis and Clark County, MT

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.

Lewis and Clark County, Montana is in USDA Zone 4b. The average last spring frost is May 29 and the first fall frost is September 18, giving you a growing season of approximately 112 days.

At an elevation of 7,064 feet, Lewis and Clark County receives approximately 22.2 inches of rainfall annually with predominantly loam soil. Summer highs average 82ยฐF, so choose short-season varieties of Mitsuba to ensure they mature before fall.

Lewis and Clark County, MT (Zone 4b) Short season
112 days
Last Spring Frost May 29
112 growing days
First Fall Frost September 18

Lewis and Clark County Soil Profile

Soil Type

Loam

Soil pH

6.5-8.1

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (9 days to spare)
Start indoors: Apr 6 Transplant: May 11 🍅 Harvest: Jul 6 – Aug 31
Recommended (50%) ✓ Fits season (7 days to spare)
Start indoors: Apr 17 Transplant: May 22 🍅 Harvest: Jul 17 – Sep 11
Safe Start (90%) ✓ Fits season (1 days to spare)
Start indoors: May 8 Transplant: Jun 12 🍅 Harvest: Aug 7 – Oct 2

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.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.8″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 200 gal / 100 sq ft
Drought risk

Water stress score is 8/10 โ€” consider drought-tolerant varieties and mulching

Mitsuba needs ~690 GDD — county provides 1,288 GDD Excellent fit

Mitsuba Planting Timeline โ€” Lewis and Clark County, MT

Mitsuba Planting Calendar

Activity When Date Range
Start Indoors April 17 Apr 17 โ€“ May 1
Transplant Outdoors May 22 May 22 โ€“ Jun 5
Direct Sow May 22 May 22 โ€“ Jun 12
Fall Sowing June 26 Jun 26 โ€“ Jul 10
Harvest July 17 Jul 17 โ€“ Sep 11

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

Month-by-Month Timeline

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

Growing Conditions

Sun

Partial Shade (3-6 hours)

Water

Moderate โ€” regular watering

Days to Maturity

50โ€“70 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 4b

Growing Season

112 days

Growing Tips for Lewis and Clark County

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

Level Up Your Garden

Frequently Asked Questions

When should I plant Mitsuba in Lewis and Clark County, MT?

Lewis and Clark County is in Zone 4b with an average last frost of May 29. Plan your Mitsuba planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Lewis and Clark County, MT?

Lewis and Clark County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is May 29 and first fall frost is September 18.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Lewis and Clark County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.

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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 Lewis and Clark County, MT. Local conditions may vary. Last updated: April 2026.