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When to Plant Mitsuba in Jefferson 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.

Jefferson County, Montana is in USDA Zone 4b. The average last spring frost is June 15 and the first fall frost is September 7, giving you a growing season of approximately 84 days.

At an elevation of 7,214 feet, Jefferson County receives approximately 21.5 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.

Jefferson County, MT (Zone 4b) Very short season
84 days
Last Spring Frost June 15
84 growing days
First Fall Frost September 7

Jefferson County Soil Profile

Soil Type

Loam

Soil pH

6.4-7.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 28 Transplant: Jun 2 🍅 Harvest: Jul 28 – Sep 22
Recommended (50%) ✗ May not fit
Start indoors: May 4 Transplant: Jun 8 🍅 Harvest: Aug 3 – Sep 28
Safe Start (90%) ✗ May not fit
Start indoors: May 12 Transplant: Jun 16 🍅 Harvest: Aug 11 – Oct 6

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
1.1″/week
You supply
0.3″/week
Watering frequency Only during dry spells
Season total 202 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 966 GDD Excellent fit

Mitsuba Planting Timeline โ€” Jefferson County, MT

Mitsuba Planting Calendar

Activity When Date Range
Start Indoors May 4 May 4 โ€“ May 18
Transplant Outdoors June 8 Jun 8 โ€“ Jun 22
Direct Sow June 8 Jun 8 โ€“ Jun 29
Fall Sowing June 15 Jun 15 โ€“ Jun 29
Harvest August 3 Aug 3 โ€“ Sep 28

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

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March โ€”
April โ€”
May Start Indoors
June Transplant Outdoors Direct Sow Fall Sowing
July โ€”
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

84 days

Growing Tips for Jefferson 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 Jefferson County, MT?

Jefferson County is in Zone 4b with an average last frost of June 15. Plan your Mitsuba planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Jefferson County, MT?

Jefferson County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is June 15 and first fall frost is September 7.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Jefferson 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 Jefferson County, MT. Local conditions may vary. Last updated: April 2026.