When to Plant Shiso in Kalawao County, HI
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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.
Kalawao County, Hawaii is in USDA Zone 11a. The average last spring frost is January 1 and the first fall frost is December 31, giving you a growing season of approximately 364 days.
At an elevation of 402 feet, Kalawao County receives approximately 28.4 inches of rainfall annually with predominantly silty clay soil. Summer highs average 85°F, providing good warmth for Shiso during the growing season. Clay soil retains moisture well for Shiso, but amend with compost to improve drainage and prevent root rot.
Kalawao County Soil Profile
Soil Type
Silty Clay
Soil pH
5.7-6.7
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 Kalawao County
How your county's soil matches Shiso's growing requirements.
Soil pH
Your soil pH (5.7–6.7) is within Shiso's preferred range (5.5–7.0).
Soil Texture
Your silty clay soil in Kalawao County is workable for Shiso. Add compost annually to improve structure.
Organic Matter
Organic matter is moderate (3.9%). Annual compost additions will help Shiso.
How to Plant Shiso
Plant Water Budget
Water stress score is 6/10 — 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 | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Feb | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| Mar | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Apr | 4.3" | 2.6" | 1.7" | 💧 Light watering |
| May | 4.3" | 1.6" | 2.7" | 🚿 Regular watering |
| Jun | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Jul | 4.3" | 0.7" | 3.6" | 🚿 Regular watering |
| Aug | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Sep | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| Oct | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| Nov | 4.3" | 2.9" | 1.4" | 💧 Light watering |
| Dec | 4.3" | 4" | 0.3" | 💧 Light watering |
Water needs are for active growing months only (Jan–Dec in Kalawao 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 — Kalawao County, HI
Shiso Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | November 20 | Nov 20 – Dec 4 |
| Transplant Outdoors | January 8 | Jan 8 – Jan 22 |
| Direct Sow | January 8 | Jan 8 – Jan 29 |
| Harvest | March 5 | Mar 5 – Apr 30 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Transplant Outdoors Direct Sow |
| February | — |
| March | Harvest |
| April | Harvest |
| May | — |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | Start Indoors |
| December | Start Indoors |
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: ideal
🗺️ USDA Zone
Zone 11a
📆 Growing Season
364 days in Kalawao County
Growing Tips for Shiso in Kalawao County
With Kalawao County's clay soil (37% clay), work in 3-4 inches of compost before planting Shiso. Avoid tilling when soil is wet to prevent compaction.
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 Kalawao County, HI?
Kalawao County is in Zone 11a with an average last frost of January 1. Plan your Shiso planting based on this frost date — see the calendar above for exact timing.
What planting zone is Kalawao County, HI?
Kalawao County, Hawaii is in USDA Hardiness Zone 11a. The average last spring frost is January 1 and first fall frost is December 31.
Your Kalawao County Garden Planner — Free
A 24-page printable planner built for Kalawao County (Zone 11a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.