When to Plant Shiso in Washington County, UT
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.
Washington County, Utah is in USDA Zone 8a. The average last spring frost is April 6 and the first fall frost is November 1, giving you a growing season of approximately 209 days.
At an elevation of 3,524 feet, Washington County receives approximately 12.7 inches of rainfall annually with predominantly loam soil. Summer highs average 90°F, providing good warmth for Shiso during the growing season. With low rainfall, drip irrigation is essential for growing Shiso successfully. Mulch heavily to conserve soil moisture.
Washington County Soil Profile
Soil Type
Loam
Soil pH
6.7-8
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 Washington County
How your county's soil matches Shiso's growing requirements.
Soil pH
Your soil pH (6.7–8.0) is more alkaline than Shiso prefers (5.5–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Washington County is excellent for Shiso — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Shiso.
Organic Matter
Organic matter is moderate (2.4%). Annual compost additions will help Shiso.
How to Plant Shiso
Succession Planting Shiso
Sow every 5.7 weeks. Last sowing by Aug 23 to harvest before frost.
Plant Water Budget
Water stress score is 10/10 — consider drought-tolerant varieties and mulching
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" | 0" | ❄️ Dormant |
| Feb | — | 0.6" | 0" | ❄️ Dormant |
| Mar | — | 1.1" | 0" | ❄️ Dormant |
| Apr | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| May | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| Jun | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Jul | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| Aug | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| Sep | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Oct | 4.3" | 1.2" | 3.1" | 🚿 Regular watering |
| Nov | 4.3" | 1" | 3.3" | 🚿 Regular watering |
| Dec | — | 0.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Nov in Washington 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 — Washington County, UT
Shiso Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 16 | Feb 16 – Mar 2 |
| Transplant Outdoors | April 20 | Apr 20 – May 4 |
| Direct Sow | April 13 | Apr 13 – May 4 |
| Harvest | June 15 | Jun 15 – Aug 10 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Harvest |
| August | 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 5.5–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 8a
📆 Growing Season
209 days in Washington County
Growing Tips for Shiso in Washington County
Direct sow Shiso outdoors after April 06 in Washington County when soil has warmed and frost danger has passed.
Washington County receives only 13" of rain annually. Shiso needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
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 Washington County, UT?
Washington County is in Zone 8a with an average last frost of April 6. Plan your Shiso planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, UT?
Washington County, Utah is in USDA Hardiness Zone 8a. The average last spring frost is April 6 and first fall frost is November 1.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Washington County gardeners in Zone 8a organize planting dates, track what's growing, and never miss a planting window.
Get Your Free Garden Planner →Free download. Plan your entire garden season in minutes.