When to Plant Shiso in Mackinac County, MI
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.
Mackinac County, Michigan is in USDA Zone 4b. The average last spring frost is May 12 and the first fall frost is October 10, giving you a growing season of approximately 151 days.
At an elevation of 1,335 feet, Mackinac County receives approximately 35.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 80°F, so choose short-season varieties of Shiso to ensure they mature before fall.
Mackinac County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-6.9
Drainage
Well Drained
Plant Planting Risk Windows
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 Mackinac County
How your county's soil matches Shiso's growing requirements.
Soil pH
Your soil pH (6.2–6.9) is within Shiso's preferred range (5.5–7.0).
Soil Texture
The silt loam soil in Mackinac County is excellent for Shiso — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.1%) — Shiso will thrive.
How to Plant Shiso
Succession Planting Shiso
Sow every 5.7 weeks. Last sowing by Aug 01 to harvest before frost.
Plant Water Budget
Monthly Watering Guide for Shiso
Shiso needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Shiso Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.5" | 0" | ❄️ Dormant |
| Apr | — | 3.3" | 0" | ❄️ Dormant |
| May | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Jun | 4.3" | 4.5" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 4" | 0.3" | 💧 Light watering |
| Aug | 4.3" | 3.6" | 0.7" | 💧 Light watering |
| Sep | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| Oct | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| Nov | — | 2.7" | 0" | ❄️ Dormant |
| Dec | — | 2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Mackinac County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Shiso 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.
Shiso Planting Timeline — Mackinac County, MI
Shiso Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 17 | Mar 17 – Mar 31 |
| Transplant Outdoors | June 2 | Jun 2 – Jun 16 |
| Direct Sow | May 19 | May 19 – Jun 9 |
| Harvest | July 28 | Jul 28 – Sep 22 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | — |
| May | Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Partial Shade (3-6 hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
50–70 days
🧪 Soil pH
Needs 5.5–7 · Your soil: ideal
🗺️ USDA Zone
Zone 4b
📆 Growing Season
151 days in Mackinac County
Growing Tips for Shiso in Mackinac County
Direct sow Shiso outdoors after May 12 in Mackinac County when soil has warmed and frost danger has passed.
General growing tips
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
Check more plant combinations with our Companion Planting Checker →
Shiso in Other Locations
Frequently Asked Questions
When should I plant Shiso in Mackinac County, MI?
Mackinac County is in Zone 4b with an average last frost of May 12. Plan your Shiso planting based on this frost date — see the calendar above for exact timing.
What planting zone is Mackinac County, MI?
Mackinac County, Michigan is in USDA Hardiness Zone 4b. The average last spring frost is May 12 and first fall frost is October 10.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Mackinac County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.
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