When to Plant Borage in Knox County, IL
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.
Knox County, Illinois is in USDA Zone 5a. The average last spring frost is April 17 and the first fall frost is October 15, giving you a growing season of approximately 181 days.
At an elevation of 1,301 feet, Knox County receives approximately 33.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Borage to ensure they mature before fall.
Knox County Soil Profile
Soil Type
Silt Loam
Soil pH
6-6.8
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 Knox County
How your county's soil matches Borage's growing requirements.
Soil pH
Your soil pH (6.0–6.8) is within Borage's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in Knox County is excellent for Borage — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.5%) — Borage will thrive.
How to Plant Borage
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Succession Planting Borage
Sow every 5.7 weeks. Last sowing by Aug 16 to harvest before frost.
For a dedicated fall crop, sow by Aug 06.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
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 | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 1.5" | 0" | ❄️ Dormant |
| Mar | — | 2.4" | 0" | ❄️ Dormant |
| Apr | 2.2" | 3.4" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 3.9" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 4.1" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 3.5" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 2.6" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 2.7" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.5" | 0" | ❄️ Dormant |
| Dec | — | 1.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Knox 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 — Knox County, IL
Borage Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 13 | Mar 13 – Mar 27 |
| Transplant Outdoors | April 10 | Apr 10 – Apr 24 |
| Direct Sow | April 3 | Apr 3 – Apr 24 |
| Harvest | June 5 | Jun 5 – Jul 24 |
| Fall Sowing | August 6 | Aug 6 – Aug 20 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Fall Sowing |
| September | — |
| October | — |
| November | — |
| December | — |
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: ideal
🗺️ USDA Zone
Zone 5a
📆 Growing Season
181 days in Knox County
Growing Tips for Borage in Knox County
Direct sow Borage outdoors after April 17 in Knox County when soil has warmed and frost danger has passed.
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 Knox County, IL?
Knox County is in Zone 5a with an average last frost of April 17. Plan your Borage planting based on this frost date — see the calendar above for exact timing.
What planting zone is Knox County, IL?
Knox County, Illinois is in USDA Hardiness Zone 5a. The average last spring frost is April 17 and first fall frost is October 15.
Plan Your Garden with Confidence
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