When to Plant Blueberries in Knox County, IL
Blueberries are long-lived shrubs producing sweet, antioxidant-rich berries. They require acidic soil and are attractive ornamental plants with fall color and spring flowers.
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 Blueberries 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.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Blueberries Planting Timeline — Knox County, IL
Blueberries Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 8 | May 8 – May 22 |
· 48" apart · Rows 72" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | — |
| July | — |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
730–1095 days
Soil pH
4.5 – 5.5
USDA Zone
Zone 5a
Growing Season
181 days
Growing Tips for Knox County
Plant at least two varieties for cross-pollination. Acidify soil with sulfur or pine needle mulch to maintain pH 4.5-5.5. Protect ripening berries from birds with netting.
Companion Planting
Good Companions
Level Up Your Garden
Blueberries in Other Locations
Frequently Asked Questions
When should I plant Blueberries in Knox County, IL?
Knox County is in Zone 5a with an average last frost of April 17. Plan your Blueberries 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
Get our free Garden Planner — designed to help Knox County gardeners in Zone 5a 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.