When to plant Leeks in Iroquois County, IL
In Iroquois County, plant Leeks in spring between April 4 and April 25, once soil temps hold above 50°F. Iroquois County's last frost averages April 18, so time plantings around the expected last-frost window for best survival. For a fall crop, sow between August 4 and August 18 — roughly 90–150 days before the first frost on October 13.
When to Plant Leeks in Iroquois County, IL
Your July game plan for Iroquois County, Illinois
Welcome to July in Zone 5b. These are the moves that will have the biggest impact on your growing season.
-
Harvest leeks as they ripen
The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.
August will be here before you know it — start on
- First harvests: leeks
- Fall sowing: leeks
Leeks are a mild, sweet allium that produces long white shanks. They are more refined than onions and are a key ingredient in soups, stews, and gratins.
Iroquois County, Illinois is in USDA Zone 5b. The average last spring frost is April 18 and the first fall frost is October 13, giving you a growing season of approximately 178 days.
At an elevation of 1,345 feet, Iroquois County receives approximately 30 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Leeks during the growing season.
Iroquois County Soil Profile
Soil Type
Silt Loam
Soil pH
5.9-6.7
Drainage
Well Drained
Leeks 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 Iroquois County
How your county's soil matches Leeks's growing requirements.
Soil pH
Your soil pH (5.9–6.7) overlaps with Leeks's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Iroquois County is excellent for Leeks — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Leeks.
Organic Matter
Organic matter is excellent (4.5%) — Leeks will thrive.
How to Plant Leeks
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Leeks Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Leeks
Leeks needs approximately 0.8 inches of water per week (3.5" per month). Here's how your county's rainfall compares month by month.
| Month | Leeks Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.3" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 1.9" | 0" | ❄️ Dormant |
| Apr | 3.5" | 2.8" | 0.7" | 💧 Light watering |
| May | 3.5" | 3.8" | 0" | ✅ Rainfall sufficient |
| Jun | 3.5" | 3.6" | 0" | ✅ Rainfall sufficient |
| Jul | 3.5" | 3" | 0.5" | 💧 Light watering |
| Aug | 3.5" | 2.9" | 0.6" | 💧 Light watering |
| Sep | 3.5" | 3.2" | 0.3" | 💧 Light watering |
| Oct | 3.5" | 2.5" | 1" | 💧 Light watering |
| Nov | — | 2" | 0" | ❄️ Dormant |
| Dec | — | 1.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Iroquois County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Leeks 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.
Leeks Planting Timeline — Iroquois County, IL
Leeks Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 14 | Mar 14 – Mar 28 |
| Transplant Outdoors | April 18 | Apr 18 – May 2 |
| Direct Sow | April 4 | Apr 4 – Apr 25 |
| Harvest | July 18 | Jul 18 – Oct 3 |
| Fall Sowing | August 4 | Aug 4 – Aug 18 |
Plant 1" deep · 15" apart · Rows 24" 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 | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.8"/week · 1-2 times/week
📅 Days to Maturity
90–150 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 5b
📆 Growing Season
178 days in Iroquois County
Growing Tips for Leeks in Iroquois County
Direct sow Leeks outdoors after April 18 in Iroquois County when soil has warmed and frost danger has passed.
Common pests for Leeks in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 10-12 weeks before last frost. Transplant into trenches and hill soil around stems as they grow to increase the white portion. Harvest as needed.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Leeks in Other Locations
Frequently Asked Questions
When should I plant Leeks in Iroquois County, IL?
Iroquois County is in Zone 5b with an average last frost of April 18. Plan your Leeks planting based on this frost date — see the calendar above for exact timing.
What planting zone is Iroquois County, IL?
Iroquois County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 18 and first fall frost is October 13.
When should I plant Leeks in Iroquois County, IL?
In Iroquois County, IL, plant Leeks after the last frost (around April 18) and before the first frost (around October 13). Best results when soil holds above 50°F.
What growing zone is Iroquois County, IL for Leeks?
Iroquois County sits in USDA Zone 5b. Leeks grows reliably in zones 3a through 10b, so it's a good fit here.
Can Leeks grow in Iroquois County's climate?
Yes — Leeks grows well in Iroquois County's temperate climate. Iroquois County averages a 178-day frost-free season, with last frost around April 18 and first frost around October 13.
Your Iroquois County Garden Planner — Free
A 22-page printable planner built for Iroquois 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.