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When to Plant Leeks in Oneida County, WI

Oneida County, Wisconsin Zone 4b May

What to do in May

May is a pivotal month for Oneida County, Wisconsin gardens. Focus on these tasks first and you'll set up the rest of the season for success.

Avg. last frost May 20
Avg. first frost September 28
Soil temp (4") 55°F
Watering Low
Pest pressure Low
Daylight 14.7 hrs
  1. Time to transplant leeks

    Harden off for 7 days — a little more sun each day — before planting. That's the difference between a seedling that thrives and one that stalls.

  2. Outdoor sowing time: leeks

    Sow every 2 weeks for a continuous harvest. A single big planting means a single big glut.

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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.

Oneida County, Wisconsin is in USDA Zone 4b. The average last spring frost is May 20 and the first fall frost is September 28, giving you a growing season of approximately 131 days.

At an elevation of 569 feet, Oneida County receives approximately 39.8 inches of rainfall annually with predominantly silt loam soil. Summer highs average 82°F, so choose short-season varieties of Leeks to ensure they mature before fall.

Oneida County, WI (Zone 4b) Short season
131 days
Last Spring Frost May 20
131 growing days
First Fall Frost September 28
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Oneida County Soil Profile

Soil Type

Silt Loam

Soil pH

6.3-7.1

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 3 Transplant: May 15 🍅 Harvest: Aug 14 – Oct 9
Recommended (50%) ✗ May not fit
Start indoors: Apr 8 Transplant: May 20 🍅 Harvest: Aug 19 – Oct 14
Safe Start (90%) ✗ May not fit
Start indoors: Apr 21 Transplant: Jun 2 🍅 Harvest: Sep 1 – Oct 27

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 Oneida County

How your county's soil matches Leeks's growing requirements.

Soil pH

Your soil pH (6.3–7.1) overlaps with Leeks's range (6.0–7.0), though not a perfect match.

Soil Texture

The silt loam soil in Oneida County is excellent for Leeks — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is excellent (4.3%) — Leeks will thrive.

How to Plant Leeks

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Fall planting: Sow 12 weeks before your first frost date for a fall harvest.

Plant Water Budget

Plant needs
0.8″/week
Rainfall provides
1.3″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft

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 1.9" 0" ❄️ Dormant
Feb 1.6" 0" ❄️ Dormant
Mar 2.7" 0" ❄️ Dormant
Apr 4.2" 0" ❄️ Dormant
May 3.5" 4.9" 0" ✅ Rainfall sufficient
Jun 3.5" 4.6" 0" ✅ Rainfall sufficient
Jul 3.5" 4.4" 0" ✅ Rainfall sufficient
Aug 3.5" 3.9" 0" ✅ Rainfall sufficient
Sep 3.5" 3.5" 0" ✅ Rainfall sufficient
Oct 3.3" 0" ❄️ Dormant
Nov 2.5" 0" ❄️ Dormant
Dec 2.3" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Oneida 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 needs ~1,380 GDD — county provides 1,506 GDD Good fit

Leeks Planting Timeline — Oneida County, WI

Leeks Planting Calendar

Activity When Date Range
Start Indoors April 8 Apr 8 – Apr 22
Transplant Outdoors May 20 May 20 – Jun 3
Direct Sow May 13 May 13 – Jun 3
Harvest August 19 Aug 19 – Oct 14
Fall Sowing July 6 Jul 6 – Jul 20

Plant 1" deep · 15" apart · Rows 24" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April Start Indoors
May Transplant Outdoors Direct Sow
June Transplant Outdoors Direct Sow
July Fall Sowing
August Harvest
September Harvest
October Harvest
November
December
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Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.8"/week · Natural rainfall sufficient

📅 Days to Maturity

90–150 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 4b

📆 Growing Season

131 days in Oneida County

Growing Tips for Leeks in Oneida County

Direct sow Leeks outdoors after May 20 in Oneida County when soil has warmed and frost danger has passed.

Your 131.0-day growing season in Oneida County is tight for Leeks (90.0-150.0 days to maturity). Start indoors and choose early-maturing varieties.

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

  • Peas
  • Green Beans

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Leeks in Oneida County, WI?

Oneida County is in Zone 4b with an average last frost of May 20. Plan your Leeks planting based on this frost date — see the calendar above for exact timing.

What planting zone is Oneida County, WI?

Oneida County, Wisconsin is in USDA Hardiness Zone 4b. The average last spring frost is May 20 and first fall frost is September 28.

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Your Oneida County Garden Planner — Free

A 24-page printable planner built for Oneida County (Zone 4b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Oneida County, WI. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.