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When to plant Leeks in Judith Basin County, MT

Aim to plant Leeks in Judith Basin County on or after May 16; the window stays open through June 6. Judith Basin County's 119-day frost-free season gives you just enough for one full spring planting. A second sowing from June 27 to July 11 extends the harvest into fall.

When to Plant Leeks in Judith Basin County, MT

Leeks
Judith Basin County, Montana Zone 4b June

June in the garden — Judith Basin County, Montana

Your garden in Judith Basin County, Montana is working on a schedule, even when you're not. Here's where you should be this June.

Avg. last frost May 23
Avg. first frost September 19
Soil temp (4") 46°F
Watering High
Pest pressure High
Daylight 15.7 hrs
  1. Start your fall crops: leeks

    A row cover ready in the garage extends your harvest by weeks once the nights turn cold.

A few tasks this June that'll pay off in July
  • 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.

Judith Basin County, Montana is in USDA Zone 4b. The average last spring frost is May 23 and the first fall frost is September 19, giving you a growing season of approximately 119 days.

At an elevation of 6,308 feet, Judith Basin County receives approximately 17.7 inches of rainfall annually with predominantly loam soil. Summer highs average 80°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.

Judith Basin County, MT (Zone 4b) Short season
119 days
Last Spring Frost May 23
119 growing days
First Fall Frost September 19

Judith Basin County Soil Profile

Soil Type

Loam

Soil pH

6.5-8.2

Drainage

Well Drained

Leeks Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 4 Transplant: May 16 🍅 Harvest: Aug 15 – Oct 10
Recommended (50%) ✗ May not fit
Start indoors: Apr 11 Transplant: May 23 🍅 Harvest: Aug 22 – Oct 17
Safe Start (90%) ✗ May not fit
Start indoors: Apr 28 Transplant: Jun 9 🍅 Harvest: Sep 8 – Nov 3

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 Judith Basin County

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

Soil pH

Your soil pH (6.5–8.2) is more alkaline than Leeks prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

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 12 weeks before your first frost date for a fall harvest.

Leeks 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 223 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 1.2" 0" ❄️ Dormant
Feb 0.9" 0" ❄️ Dormant
Mar 1.4" 0" ❄️ Dormant
Apr 1.9" 0" ❄️ Dormant
May 3.5" 2.2" 1.3" 💧 Light watering
Jun 3.5" 1.3" 2.2" 🚿 Regular watering
Jul 3.5" 1.7" 1.8" 🚿 Regular watering
Aug 3.5" 1.9" 1.6" 💧 Light watering
Sep 3.5" 1.4" 2.1" 🚿 Regular watering
Oct 1.7" 0" ❄️ Dormant
Nov 1.1" 0" ❄️ Dormant
Dec 1.1" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Judith Basin 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 ~1,200 GDD — county provides 1,190 GDD Tight fit

Leeks Planting Timeline — Judith Basin County, MT

Leeks Planting Calendar

Activity When Date Range
Start Indoors April 11 Apr 11 – Apr 25
Transplant Outdoors May 23 May 23 – Jun 6
Direct Sow May 16 May 16 – Jun 6
Harvest August 22 Aug 22 – Oct 17
Fall Sowing June 27 Jun 27 – Jul 11

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 Fall Sowing
July Fall Sowing
August 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: too_alkaline

🗺️ USDA Zone

Zone 4b

📆 Growing Season

119 days in Judith Basin County

Growing Tips for Leeks in Judith Basin County

Direct sow Leeks outdoors after May 23 in Judith Basin County when soil has warmed and frost danger has passed.

Your 119.0-day growing season in Judith Basin 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 Judith Basin County, MT?

Judith Basin County is in Zone 4b with an average last frost of May 23. Plan your Leeks planting based on this frost date — see the calendar above for exact timing.

What planting zone is Judith Basin County, MT?

Judith Basin County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is May 23 and first fall frost is September 19.

When should I plant Leeks in Judith Basin County, MT?

In Judith Basin County, MT, plant Leeks after the last frost (around May 23) and before the first frost (around September 19). Best results when soil holds above 50°F.

What growing zone is Judith Basin County, MT for Leeks?

Judith Basin County sits in USDA Zone 4b. Leeks grows reliably in zones 3a through 10b, so it's a good fit here.

Can Leeks grow in Judith Basin County's climate?

Yes — Leeks grows well in Judith Basin County's temperate climate. Judith Basin County averages a 119-day frost-free season, with last frost around May 23 and first frost around September 19.

🌱

Your Judith Basin County Garden Planner — Free

A 22-page printable planner built for Judith Basin 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 Judith Basin County, MT. Local conditions may vary. Last updated: June 2026.

Sources & credits

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