When to Plant Onion in Boone County, IN
Onions are a fundamental kitchen staple available in yellow, white, and red varieties. Choose long-day, short-day, or intermediate types based on your latitude.
Boone County, Indiana is in USDA Zone 5b. The average last spring frost is April 22 and the first fall frost is October 15, giving you a growing season of approximately 176 days.
At an elevation of 850 feet, Boone County receives approximately 35.3 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Onion to ensure they mature before fall.
Boone County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-6.8
Drainage
Well Drained
Monthly Watering Guide for Onion
Onion needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Onion Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.6" | 0" | ❄️ Dormant |
| Mar | — | 2.6" | 0" | ❄️ Dormant |
| Apr | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| May | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Jun | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Jul | 4.3" | 4" | 0.3" | 💧 Light watering |
| Aug | 4.3" | 3.3" | 1" | 💧 Light watering |
| Sep | 4.3" | 3.4" | 0.9" | 💧 Light watering |
| Oct | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| Nov | — | 2.3" | 0" | ❄️ Dormant |
| Dec | — | 1.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Boone County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion Planting Timeline — Boone County, IN
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 18 | Mar 18 – Apr 1 |
| Transplant Outdoors | April 22 | Apr 22 – May 6 |
| Direct Sow | April 8 | Apr 8 – Apr 29 |
| Harvest | July 22 | Jul 22 – Sep 9 |
| Fall Sowing | August 6 | Aug 6 – Aug 20 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors |
| June | — |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 5b
📆 Growing Season
176 days in Boone County
Growing Tips for Boone County
Start seeds indoors 8-10 weeks before transplanting. Match day-length type to your latitude. Stop watering when tops begin to fall over and cure bulbs for 2-3 weeks before storage.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Boone County, IN?
Boone County is in Zone 5b with an average last frost of April 22. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Boone County, IN?
Boone County, Indiana is in USDA Hardiness Zone 5b. The average last spring frost is April 22 and first fall frost is October 15.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Boone County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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