When to Plant Onion in Lake 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.
Lake County, Illinois is in USDA Zone 5b. The average last spring frost is April 21 and the first fall frost is October 20, giving you a growing season of approximately 182 days.
At an elevation of 1,080 feet, Lake County receives approximately 33.5 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.
Lake County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-6.9
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
Onion Planting Timeline — Lake County, IL
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 17 | Mar 17 – Mar 31 |
| Transplant Outdoors | April 21 | Apr 21 – May 5 |
| Direct Sow | April 7 | Apr 7 – Apr 28 |
| Fall Sowing | August 11 | Aug 11 – Aug 25 |
| Harvest | July 21 | Jul 21 – Sep 8 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | 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
6 – 7
USDA Zone
Zone 5b
Growing Season
182 days
Growing Tips for Lake 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
Level Up Your Garden
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Lake County, IL?
Lake County is in Zone 5b with an average last frost of April 21. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Lake County, IL?
Lake County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 21 and first fall frost is October 20.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Lake County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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