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When to Plant Fennel in Prowers County, CO

Prowers County, Colorado Zone 6a May

Your May gardening checklist

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

Avg. last frost April 30
Avg. first frost October 10
Soil temp (4") 44°F
Watering High
Pest pressure Low
Daylight 14.1 hrs
  1. Set out fennel seedlings

    Pinch off the lowest leaves on each seedling before you plant — it reduces water loss while the roots catch up.

  2. Scatter fennel into prepared beds

    Keep the top inch of soil moist until germination — a gentle morning watering for 5–7 days does the job.

Looking ahead to June
  • Starting indoors: fennel

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Florence fennel is grown for its swollen bulb-like stem base, which has a mild anise flavor. It is crisp raw in salads and sweet when roasted or braised.

Prowers County, Colorado is in USDA Zone 6a. The average last spring frost is April 30 and the first fall frost is October 10, giving you a growing season of approximately 163 days.

At an elevation of 6,074 feet, Prowers County receives approximately 24.7 inches of rainfall annually with predominantly loam soil. Summer highs average 88°F, providing good warmth for Fennel during the growing season.

Prowers County, CO (Zone 6a) Moderate season
163 days
Last Spring Frost April 30
163 growing days
First Fall Frost October 10

Prowers County Soil Profile

Soil Type

Loam

Soil pH

6.2-8.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (44 days to spare)
Start indoors: Mar 1 Transplant: May 10 🍅 Harvest: Jul 12 – Aug 23
Recommended (50%) ✓ Fits season (44 days to spare)
Start indoors: Mar 5 Transplant: May 14 🍅 Harvest: Jul 16 – Aug 27
Safe Start (90%) ✓ Fits season (45 days to spare)
Start indoors: Mar 18 Transplant: May 27 🍅 Harvest: Jul 29 – Sep 9

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 Prowers County

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

Soil pH

Your soil pH (6.2–8.3) is more alkaline than Fennel prefers (5.5–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.1%). Annual compost additions will help Fennel.

How to Plant Fennel

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

Succession Planting Fennel

3
successive plantings in your 163-day season

Sow every 6.9 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 Fennel

Fennel 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 Fennel Needs Rainfall You Supplement Action
Jan 1.5" 0" ❄️ Dormant
Feb 1.5" 0" ❄️ Dormant
Mar 2.1" 0" ❄️ Dormant
Apr 2.6" 2.8" 0" ✅ Rainfall sufficient
May 2.6" 2.6" 0" ✅ Rainfall sufficient
Jun 2.6" 1.5" 1.1" 💧 Light watering
Jul 2.6" 2.1" 0.5" 💧 Light watering
Aug 2.6" 2.9" 0" ✅ Rainfall sufficient
Sep 2.6" 2.3" 0.3" 💧 Light watering
Oct 2.6" 2.4" 0.2" 💧 Light watering
Nov 1.6" 0" ❄️ Dormant
Dec 1.4" 0" ❄️ Dormant

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

Fennel 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.

Fennel needs ~1,200 GDD — county provides 2,608 GDD Excellent fit

Fennel Planting Timeline — Prowers County, CO

Fennel Planting Calendar

Activity When Date Range
Start Indoors March 5 Mar 5 – Mar 19
Transplant Outdoors May 14 May 14 – May 28
Direct Sow May 7 May 7 – May 28
Harvest July 16 Jul 16 – Aug 27

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.6"/week · Natural rainfall sufficient

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 5.5–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 6a

📆 Growing Season

163 days in Prowers County

Growing Tips for Fennel in Prowers County

Direct sow Fennel outdoors after April 30 in Prowers County when soil has warmed and frost danger has passed.

Common pests for Fennel in this region include carrot rust fly and parsleyworm. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow in late summer for fall harvest to reduce bolting. Hill soil around bulbs as they enlarge. Harvest when bulbs are tennis-ball sized before they elongate.

Companion Planting

Good Companions

Avoid Planting Near

  • Tomatoes
  • Peppers
  • Beans

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Fennel in Prowers County, CO?

Prowers County is in Zone 6a with an average last frost of April 30. Plan your Fennel planting based on this frost date — see the calendar above for exact timing.

What planting zone is Prowers County, CO?

Prowers County, Colorado is in USDA Hardiness Zone 6a. The average last spring frost is April 30 and first fall frost is October 10.

🌱

Your Prowers County Garden Planner — Free

A 24-page printable planner built for Prowers 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 Prowers 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.