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When to Plant Basil in Fremont County, CO

Fremont County, Colorado Zone 6a May

May in Fremont County, Colorado — your action list

We've pulled the most time-sensitive tasks for Fremont County, Colorado this May and put them front and centre. Tackle them in order.

Avg. last frost May 23
Avg. first frost September 25
Soil temp (4") 38°F
Watering High
Pest pressure Low
Daylight 14.1 hrs
  1. Scatter basil into prepared beds

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

June will be here before you know it — start on
  • Transplants going out: basil

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Basil is a fragrant warm-season herb essential to Italian and Thai cuisines. It comes in many varieties including sweet, Thai, purple, and lemon types.

Fremont County, Colorado is in USDA Zone 6a. The average last spring frost is May 23 and the first fall frost is September 25, giving you a growing season of approximately 125 days.

At an elevation of 6,575 feet, Fremont County receives approximately 18.5 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Basil to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Basil successfully. Mulch heavily to conserve soil moisture.

Fremont County, CO (Zone 6a) Short season
125 days
Last Spring Frost May 23
125 growing days
First Fall Frost September 25
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Fremont County Soil Profile

Soil Type

Loam

Soil pH

6.7-8.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 23 Transplant: May 25 🍅 Harvest: Jul 20 – Sep 21
Recommended (50%) ✗ May not fit
Start indoors: Apr 4 Transplant: Jun 6 🍅 Harvest: Aug 1 – Oct 3
Safe Start (90%) ✗ May not fit
Start indoors: Apr 27 Transplant: Jun 29 🍅 Harvest: Aug 24 – Oct 26

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 Fremont County

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

Soil pH

Your soil pH (6.7–8.3) is more alkaline than Basil prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

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

How to Plant Basil

0.5"
Planting Depth
8"
Between Plants
12"
Between Rows

Succession Planting Basil

2
successive plantings in your 125-day season

Sow every 5.7 weeks. Last sowing by Jul 12 to harvest before frost.

Plant Water Budget

Plant needs
0.6″/week
Rainfall provides
0.6″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Basil

Basil needs approximately 0.6 inches of water per week (2.6" per month). Here's how your county's rainfall compares month by month.

Month Basil Needs Rainfall You Supplement Action
Jan 1.5" 0" ❄️ Dormant
Feb 1.1" 0" ❄️ Dormant
Mar 1.6" 0" ❄️ Dormant
Apr 2.2" 0" ❄️ Dormant
May 2.6" 2" 0.6" 💧 Light watering
Jun 2.6" 1.5" 1.1" 💧 Light watering
Jul 2.6" 1.4" 1.2" 💧 Light watering
Aug 2.6" 1.7" 0.9" 💧 Light watering
Sep 2.6" 1.5" 1.1" 💧 Light watering
Oct 1.7" 0" ❄️ Dormant
Nov 1.4" 0" ❄️ Dormant
Dec 1" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Fremont County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Basil 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.

Basil needs ~812 GDD — county provides 1,625 GDD Excellent fit

Basil Planting Timeline — Fremont County, CO

Basil Planting Calendar

Activity When Date Range
Start Indoors April 4 Apr 4 – Apr 18
Transplant Outdoors June 6 Jun 6 – Jun 20
Direct Sow May 30 May 30 – Jun 20
Harvest August 1 Aug 1 – Oct 3

Plant 0.5" deep · 8" apart · Rows 12" apart

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.6"/week · Natural rainfall sufficient

📅 Days to Maturity

50–75 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 6a

📆 Growing Season

125 days in Fremont County

Growing Tips for Basil in Fremont County

Direct sow Basil outdoors after May 23 in Fremont County when soil has warmed and frost danger has passed.

General growing tips

Start seeds indoors or direct sow after last frost. Pinch flower buds to extend leaf production. Harvest leaves from the top down, cutting just above a leaf pair.

Companion Planting

Good Companions

Avoid Planting Near

  • Rue
  • Sage

Check more plant combinations with our Companion Planting Checker →

🌾 Save Your Own Basil Seeds
Life Cycle Annual
Pollination Self-Pollinating
How to Collect Let flower spikes dry brown on the plant.
Storage Store airtight; viable 5 years at 35°F, under 45% humidity.

Isolate 150 ft between varieties. Different basil species can cross.

Frequently Asked Questions

When should I plant Basil in Fremont County, CO?

Fremont County is in Zone 6a with an average last frost of May 23. Plan your Basil planting based on this frost date — see the calendar above for exact timing.

What planting zone is Fremont County, CO?

Fremont County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is May 23 and first fall frost is September 25.

🌱

Your Fremont County Garden Planner — Free

A 24-page printable planner built for Fremont County (Zone 6a). 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 Fremont 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.