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When to Plant Shiso in Butte County, CA

Shiso (perilla) is a fragrant Japanese herb with large, ruffled leaves in green or purple varieties. It has a unique flavor combining mint, basil, and anise.

Butte County, California is in USDA Zone 9a. The average last spring frost is April 20 and the first fall frost is November 10, giving you a growing season of approximately 204 days.

At an elevation of 144 feet, Butte County receives approximately 44.8 inches of rainfall annually with predominantly loam soil. Summer highs average 90ยฐF, providing good warmth for Shiso during the growing season.

Butte County, CA (Zone 9a) Long season
204 days
Last Spring Frost April 20
204 growing days
First Fall Frost November 10

Butte County Soil Profile

Soil Type

Loam

Soil pH

6.8-7.7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (80 days to spare)
Start indoors: Feb 12 Transplant: Apr 2 🍅 Harvest: May 28 – Jul 23
Recommended (50%) ✓ Fits season (85 days to spare)
Start indoors: Mar 9 Transplant: Apr 27 🍅 Harvest: Jun 22 – Aug 17
Safe Start (90%) ✓ Fits season (85 days to spare)
Start indoors: Apr 12 Transplant: May 31 🍅 Harvest: Jul 26 – Sep 20

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
0.9″/week
You supply
0.5″/week
Watering frequency 1-2 times/week
Season total 823 gal / 100 sq ft
Drought risk

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

Shiso needs ~1,050 GDD — county provides 3,570 GDD Excellent fit

Shiso Planting Timeline โ€” Butte County, CA

Shiso Planting Calendar

Activity When Date Range
Start Indoors March 9 Mar 9 โ€“ Mar 23
Transplant Outdoors April 27 Apr 27 โ€“ May 11
Direct Sow April 27 Apr 27 โ€“ May 18
Harvest June 22 Jun 22 โ€“ Aug 17

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

Month-by-Month Timeline

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

5.5 โ€“ 7

USDA Zone

Zone 9a

Growing Season

204 days

Growing Tips for Butte County

Direct sow after last frost or start indoors. Both green and red varieties are available. Pinch tips to encourage bushiness. Self-sows prolifically; deadhead to control.

Companion Planting

Good Companions

Level Up Your Garden

Frequently Asked Questions

When should I plant Shiso in Butte County, CA?

Butte County is in Zone 9a with an average last frost of April 20. Plan your Shiso planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Butte County, CA?

Butte County, California is in USDA Hardiness Zone 9a. The average last spring frost is April 20 and first fall frost is November 10.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Butte County gardeners in Zone 9a 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 Butte County, CA. Local conditions may vary. Last updated: April 2026.