When to plant Onion in Lee County, IL
Lee County's spring Onion window runs April 8 through April 29. time plantings around the expected last-frost window for best survival. A second sowing from August 5 to August 19 extends the harvest into fall.
When to Plant Onion in Lee County, IL
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.
Lee County, Illinois is in USDA Zone 5b. The average last spring frost is April 22 and the first fall frost is October 14, giving you a growing season of approximately 175 days.
At an elevation of 1,010 feet, Lee County receives approximately 33.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Onion to ensure they mature before fall.
Lee County Soil Profile
Soil Type
Silt Loam
Soil pH
6.3-6.9
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" | 0" | ❄️ Dormant |
| Apr | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| May | 4.3" | 4.4" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 4.2" | 0.1" | 💧 Light watering |
| Jul | 4.3" | 3.3" | 1" | 💧 Light watering |
| Aug | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Sep | 4.3" | 2.9" | 1.4" | 💧 Light watering |
| Oct | 4.3" | 2.7" | 1.6" | 💧 Light watering |
| Nov | — | 2.7" | 0" | ❄️ Dormant |
| Dec | — | 1.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Lee County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion Planting Timeline — Lee County, IL
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 5 | Aug 5 – Aug 19 |
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
175 days in Lee County
Growing Tips for Lee 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 Lee County, IL?
Lee 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 Lee County, IL?
Lee County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 22 and first fall frost is October 14.
When should I plant Onion in Lee County, IL?
In Lee County, IL, plant Onion after the last frost (around April 22) and before the first frost (around October 14). Best results when soil holds above 50°F.
What growing zone is Lee County, IL for Onion?
Lee County sits in USDA Zone 5b. Onion grows reliably in zones 3a through 10b, so it's a good fit here.
Can Onion grow in Lee County's climate?
Yes — Onion grows well in Lee County's temperate climate. Lee County averages a 175-day frost-free season, with last frost around April 22 and first frost around October 14.
Your Lee County Garden Planner — Free
A 22-page printable planner built for Lee County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.