When to Plant Borage in Kauai County, HI
Borage is a self-seeding annual herb with star-shaped blue flowers that attract pollinators. Its leaves have a cucumber-like flavor and the flowers are edible.
Kauai 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 577 feet, Kauai County receives approximately 89.5 inches of rainfall annually with predominantly silty clay soil. Summer highs average 90°F, providing good warmth for Borage during the growing season. Clay soil retains moisture well for Borage, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Borage root diseases.
Kauai County Soil Profile
Soil Type
Silty Clay
Soil pH
5.5-6.7
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 Kauai County
How your county's soil matches Borage's growing requirements.
Soil pH
Your soil pH (5.5–6.7) overlaps with Borage's range (6.0–7.0), though not a perfect match.
Soil Texture
Your silty clay soil in Kauai County is workable for Borage. Add compost annually to improve structure.
Organic Matter
Organic matter is excellent (4.5%) — Borage will thrive.
How to Plant Borage
Fall planting: Sow 8 weeks before your first frost date for a fall harvest.
Plant Water Budget
Monthly Watering Guide for Borage
Borage needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Borage Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | 2.2" | 12.1" | 0" | ✅ Rainfall sufficient |
| Feb | 2.2" | 8.6" | 0" | ✅ Rainfall sufficient |
| Mar | 2.2" | 10.5" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 8.4" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 5.3" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 2.5" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 2.2" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 3.1" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 4.3" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 9.8" | 0" | ✅ Rainfall sufficient |
| Nov | 2.2" | 9.3" | 0" | ✅ Rainfall sufficient |
| Dec | 2.2" | 13.3" | 0" | ✅ Rainfall sufficient |
Water needs are for active growing months only (Jan–Dec in Kauai County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Borage 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.
Borage Planting Timeline — Kauai County, HI
Borage Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | December 4 | Dec 4 – Dec 18 |
| Transplant Outdoors | December 25 | Dec 25 – Jan 8 |
| Direct Sow | December 11 | Dec 11 – Jan 1 |
| Harvest | February 19 | Feb 19 – Apr 9 |
| Fall Sowing | November 5 | Nov 5 – Nov 19 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Transplant Outdoors Direct Sow |
| February | Harvest |
| March | Harvest |
| April | Harvest |
| May | — |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | Fall Sowing |
| December | Start Indoors Transplant Outdoors Direct Sow |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
50–60 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 11a
📆 Growing Season
364 days in Kauai County
Growing Tips for Borage in Kauai County
With Kauai County's clay soil (31% clay), work in 3-4 inches of compost before planting Borage. Avoid tilling when soil is wet to prevent compaction.
With 90" of annual rainfall in Kauai County, ensure good drainage for Borage — excess moisture can promote root rot and fungal diseases.
General growing tips
Direct sow in spring as borage does not transplant well. Allow some plants to go to seed for next year. Young leaves are best; older leaves become bristly.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Borage in Other Locations
Frequently Asked Questions
When should I plant Borage in Kauai County, HI?
Kauai County is in Zone 11a with an average last frost of January 1. Plan your Borage planting based on this frost date — see the calendar above for exact timing.
What planting zone is Kauai County, HI?
Kauai County, Hawaii is in USDA Hardiness Zone 11a. The average last spring frost is January 1 and first fall frost is December 31.
Plan Your Garden with Confidence
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