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When to Plant Leeks in Sheridan County, WY

Sheridan County, Wyoming Zone 5a May

This month in Sheridan County, Wyoming

May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Sheridan County, Wyoming.

Avg. last frost May 20
Avg. first frost September 20
Soil temp (4") 41°F
Watering High
Pest pressure Low
Daylight 14.6 hrs
  1. Move leeks from tray to bed

    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

    Thin ruthlessly once seedlings are up. Crowded roots mean smaller crops from every plant.

Looking ahead to June
  • Starting indoors: leeks

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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.

Sheridan County, Wyoming is in USDA Zone 5a. The average last spring frost is May 20 and the first fall frost is September 20, giving you a growing season of approximately 123 days.

At an elevation of 5,266 feet, Sheridan County receives approximately 14.7 inches of rainfall annually with predominantly loam soil. Summer highs average 82°F, so choose short-season varieties of Leeks to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Leeks successfully. Mulch heavily to conserve soil moisture.

Sheridan County, WY (Zone 5a) Short season
123 days
Last Spring Frost May 20
123 growing days
First Fall Frost September 20

Sheridan County Soil Profile

Soil Type

Loam

Soil pH

6.6-7.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 9 Transplant: May 14 🍅 Harvest: Aug 13 – Oct 29
Recommended (50%) ✗ May not fit
Start indoors: Apr 15 Transplant: May 20 🍅 Harvest: Aug 19 – Nov 4
Safe Start (90%) ✗ May not fit
Start indoors: May 6 Transplant: Jun 10 🍅 Harvest: Sep 9 – Nov 25

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 Sheridan County

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

Soil pH

Your soil pH (6.6–7.8) is more alkaline than Leeks prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Drainage

Drainage is adequate for Leeks.

Organic Matter

Organic matter is moderate (2.6%). Annual compost additions will help Leeks.

How to Plant Leeks

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

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Plant Water Budget

Plant needs
0.8″/week
Rainfall provides
0.5″/week
You supply
0.7″/week
Watering frequency 1-2 times/week
Season total 707 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — 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 1.1" 0" ❄️ Dormant
Feb 0.9" 0" ❄️ Dormant
Mar 1.2" 0" ❄️ Dormant
Apr 1.4" 0" ❄️ Dormant
May 3.5" 1.9" 1.6" 💧 Light watering
Jun 3.5" 1" 2.5" 🚿 Regular watering
Jul 3.5" 1.1" 2.4" 🚿 Regular watering
Aug 3.5" 1.7" 1.8" 🚿 Regular watering
Sep 3.5" 1.1" 2.4" 🚿 Regular watering
Oct 1.2" 0" ❄️ Dormant
Nov 1.1" 0" ❄️ Dormant
Dec 0.9" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Sheridan 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 1,414 GDD Good fit

Leeks Planting Timeline — Sheridan County, WY

Leeks Planting Calendar

Activity When Date Range
Start Indoors April 15 Apr 15 – Apr 29
Transplant Outdoors May 20 May 20 – Jun 3
Direct Sow May 6 May 6 – May 27
Harvest August 19 Aug 19 – Nov 4
Fall Sowing July 12 Jul 12 – Jul 26

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
July Fall Sowing
August Harvest
September Harvest
October Harvest
November Harvest
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: too_alkaline

🗺️ USDA Zone

Zone 5a

📆 Growing Season

123 days in Sheridan County

Growing Tips for Leeks in Sheridan County

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

Your 123.0-day growing season in Sheridan 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 Sheridan County, WY?

Sheridan County is in Zone 5a 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 Sheridan County, WY?

Sheridan County, Wyoming is in USDA Hardiness Zone 5a. The average last spring frost is May 20 and first fall frost is September 20.

🌱

Your Sheridan County Garden Planner — Free

A 24-page printable planner built for Sheridan 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.

Instant PDF download. No spam, unsubscribe any time.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Sheridan County, WY. 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.