When to plant Leeks in Grundy County, IA
Grundy County gardeners should plant Leeks between April 14 and May 5 in spring. With Grundy County's Zone 5a climate (last frost April 28), Leeks needs 90–150 days to mature — plant by May 12 for a full harvest. A second sowing from July 31 to August 14 extends the harvest into fall.
When to Plant Leeks in Grundy County, IA
June in Grundy County, Iowa — your action list
Each item below is timed to Grundy County, Iowa's frost dates and soil temperatures. Skip nothing, stress about nothing.
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Fire up the seed-starting tray: leeks
Give them 6–8 weeks indoors before the last frost and you'll transplant into warm soil with seedlings that are already leaping.
Before July arrives, get these ready
- 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.
Grundy County, Iowa is in USDA Zone 5a. The average last spring frost is April 28 and the first fall frost is October 9, giving you a growing season of approximately 164 days.
At an elevation of 984 feet, Grundy County receives approximately 30.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Leeks to ensure they mature before fall.
Grundy County Soil Profile
Soil Type
Silt Loam
Soil pH
6-7.2
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 Grundy County
How your county's soil matches Leeks's growing requirements.
Soil pH
Your soil pH (6.0–7.2) overlaps with Leeks's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Grundy County is excellent for Leeks — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.9%). Annual compost additions will help Leeks.
How to Plant Leeks
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Leeks Water Budget
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 | — | 1.2" | 0" | ❄️ Dormant |
| Mar | — | 2.1" | 0" | ❄️ Dormant |
| Apr | 3.5" | 3.2" | 0.3" | 💧 Light watering |
| May | 3.5" | 3.3" | 0.2" | 💧 Light watering |
| Jun | 3.5" | 4.1" | 0" | ✅ Rainfall sufficient |
| Jul | 3.5" | 3.1" | 0.4" | 💧 Light watering |
| Aug | 3.5" | 3.6" | 0" | ✅ Rainfall sufficient |
| Sep | 3.5" | 2.5" | 1" | 💧 Light watering |
| Oct | 3.5" | 2.6" | 0.9" | 💧 Light watering |
| Nov | — | 1.9" | 0" | ❄️ Dormant |
| Dec | — | 1.5" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Grundy 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 — Grundy County, IA
Leeks Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 24 | Mar 24 – Apr 7 |
| Transplant Outdoors | April 28 | Apr 28 – May 12 |
| Direct Sow | April 14 | Apr 14 – May 5 |
| Harvest | July 28 | Jul 28 – Oct 13 |
| Fall Sowing | July 31 | Jul 31 – Aug 14 |
Plant 1" deep · 15" apart · Rows 24" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Fall Sowing Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.8"/week · Only during dry spells
📅 Days to Maturity
90–150 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 5a
📆 Growing Season
164 days in Grundy County
Growing Tips for Leeks in Grundy County
Direct sow Leeks outdoors after April 28 in Grundy 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 Grundy County, IA?
Grundy County is in Zone 5a with an average last frost of April 28. Plan your Leeks planting based on this frost date — see the calendar above for exact timing.
What planting zone is Grundy County, IA?
Grundy County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is April 28 and first fall frost is October 9.
When should I plant Leeks in Grundy County, IA?
In Grundy County, IA, plant Leeks after the last frost (around April 28) and before the first frost (around October 9). Best results when soil holds above 50°F.
What growing zone is Grundy County, IA for Leeks?
Grundy County sits in USDA Zone 5a. Leeks grows reliably in zones 3a through 10b, so it's a good fit here.
Can Leeks grow in Grundy County's climate?
Yes — Leeks grows well in Grundy County's temperate climate. Grundy County averages a 164-day frost-free season, with last frost around April 28 and first frost around October 9.
Your Grundy County Garden Planner — Free
A 22-page printable planner built for Grundy County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.