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When to Plant Leeks in Hinsdale County, CO

Hinsdale County, Colorado Zone 5a May

May in the garden — Hinsdale County, Colorado

A quick May briefing for Hinsdale County, Colorado gardeners — what's urgent, what's next, and what can wait.

Avg. last frost June 18
Avg. first frost September 10
Soil temp (4") 34°F
Watering High
Pest pressure Low
Daylight 14 hrs
To set up a strong June, finish these tasks
  • Transplants going out: leeks
  • Direct-sowing: 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.

Hinsdale County, Colorado is in USDA Zone 5a. The average last spring frost is June 18 and the first fall frost is September 10, giving you a growing season of approximately 84 days.

At an elevation of 6,833 feet, Hinsdale County receives approximately 23.8 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.

Hinsdale County, CO (Zone 5a) Very short season
84 days
Last Spring Frost June 18
84 growing days
First Fall Frost September 10
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Hinsdale County Soil Profile

Soil Type

Loam

Soil pH

6.8-8.1

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: May 1 Transplant: Jun 5 🍅 Harvest: Sep 4 – Nov 20
Recommended (50%) ✗ May not fit
Start indoors: May 14 Transplant: Jun 18 🍅 Harvest: Sep 17 – Dec 3
Safe Start (90%) ✗ May not fit
Start indoors: May 25 Transplant: Jun 29 🍅 Harvest: Sep 28 – Dec 14

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 Hinsdale County

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

Soil pH

Your soil pH (6.8–8.1) is more alkaline than Leeks prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.3%). 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
1.2″/week
Watering frequency Natural rainfall sufficient
Season total 0 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 1.9" 0" ❄️ Dormant
Feb 1.3" 0" ❄️ Dormant
Mar 2" 0" ❄️ Dormant
Apr 2.8" 0" ❄️ Dormant
May 2.5" 0" ❄️ Dormant
Jun 3.5" 1.4" 2.1" 🚿 Regular watering
Jul 3.5" 2.2" 1.3" 💧 Light watering
Aug 3.5" 2.7" 0.8" 💧 Light watering
Sep 3.5" 2.2" 1.3" 💧 Light watering
Oct 1.9" 0" ❄️ Dormant
Nov 1.5" 0" ❄️ Dormant
Dec 1.3" 0" ❄️ Dormant

Water needs are for active growing months only (Jun–Sep in Hinsdale 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 966 GDD May not mature

Leeks Planting Timeline — Hinsdale County, CO

Leeks Planting Calendar

Activity When Date Range
Start Indoors May 14 May 14 – May 28
Transplant Outdoors June 18 Jun 18 – Jul 2
Direct Sow June 4 Jun 4 – Jun 25
Harvest September 17 Sep 17 – Dec 3
Fall Sowing July 2 Jul 2 – Jul 16

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

Month-by-Month Timeline

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

🗺️ USDA Zone

Zone 5a

📆 Growing Season

84 days in Hinsdale County

Growing Tips for Leeks in Hinsdale County

Direct sow Leeks outdoors after June 18 in Hinsdale County when soil has warmed and frost danger has passed.

Your 84.0-day growing season in Hinsdale 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 Hinsdale County, CO?

Hinsdale County is in Zone 5a with an average last frost of June 18. Plan your Leeks planting based on this frost date — see the calendar above for exact timing.

What planting zone is Hinsdale County, CO?

Hinsdale County, Colorado is in USDA Hardiness Zone 5a. The average last spring frost is June 18 and first fall frost is September 10.

🌱

Your Hinsdale County Garden Planner — Free

A 24-page printable planner built for Hinsdale 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 Hinsdale County, CO. 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.