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When to Plant Leeks in Teton County, ID

Teton County, Idaho Zone 5a May

May to-do list for Teton County, Idaho

Welcome to May in Zone 5a. These are the moves that will have the biggest impact on your growing season.

Avg. last frost May 31
Avg. first frost September 11
Soil temp (4") 35°F
Watering High
Pest pressure Low
Daylight 14.5 hrs
  1. Harden off and plant leeks

    Water the tray well an hour before you transplant. Roots slide out cleanly and settle in faster.

  2. Seed leeks outdoors

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

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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.

Teton County, Idaho is in USDA Zone 5a. The average last spring frost is May 31 and the first fall frost is September 11, giving you a growing season of approximately 103 days.

At an elevation of 6,709 feet, Teton County receives approximately 15.1 inches of rainfall annually with predominantly loam soil. Summer highs average 83°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.

Teton County, ID (Zone 5a) Short season
103 days
Last Spring Frost May 31
103 growing days
First Fall Frost September 11
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Teton County Soil Profile

Soil Type

Loam

Soil pH

6.5-8.4

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 16 Transplant: May 21 🍅 Harvest: Aug 20 – Nov 5
Recommended (50%) ✗ May not fit
Start indoors: Apr 26 Transplant: May 31 🍅 Harvest: Aug 30 – Nov 15
Safe Start (90%) ✗ May not fit
Start indoors: May 17 Transplant: Jun 21 🍅 Harvest: Sep 20 – Dec 6

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 Teton County

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

Soil pH

Your soil pH (6.5–8.4) is more alkaline than Leeks prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.7%). 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
0.6″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 203 gal / 100 sq ft
Drought risk

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 1.1" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.2" 0" ❄️ Dormant
Apr 1.8" 0" ❄️ Dormant
May 3.5" 1.9" 1.6" 💧 Light watering
Jun 3.5" 1.1" 2.4" 🚿 Regular watering
Jul 3.5" 1.4" 2.1" 🚿 Regular watering
Aug 3.5" 1.4" 2.1" 🚿 Regular watering
Sep 3.5" 1.2" 2.3" 🚿 Regular watering
Oct 1.2" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 1" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Teton 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 ~1,470 GDD — county provides 1,261 GDD May not mature

Leeks Planting Timeline — Teton County, ID

Leeks Planting Calendar

Activity When Date Range
Start Indoors April 26 Apr 26 – May 10
Transplant Outdoors May 31 May 31 – Jun 14
Direct Sow May 17 May 17 – Jun 7
Harvest August 30 Aug 30 – Nov 15
Fall Sowing July 3 Jul 3 – Jul 17

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

Month-by-Month Timeline

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

🗺️ USDA Zone

Zone 5a

📆 Growing Season

103 days in Teton County

Growing Tips for Leeks in Teton County

Direct sow Leeks outdoors after May 31 in Teton County when soil has warmed and frost danger has passed.

Your 103.0-day growing season in Teton 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 Teton County, ID?

Teton County is in Zone 5a with an average last frost of May 31. Plan your Leeks planting based on this frost date — see the calendar above for exact timing.

What planting zone is Teton County, ID?

Teton County, Idaho is in USDA Hardiness Zone 5a. The average last spring frost is May 31 and first fall frost is September 11.

🌱

Your Teton County Garden Planner — Free

A 24-page printable planner built for Teton 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.

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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 Teton County, ID. 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.