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When to Plant Fennel in Rock County, NE

Rock County, Nebraska Zone 5a May

Rock County, Nebraska gardeners: here's your May plan

May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Rock County, Nebraska.

Avg. last frost May 10
Avg. first frost October 6
Soil temp (4") 55°F
Watering Low
Pest pressure Low
Daylight 14.4 hrs
  1. Get fennel in the ground

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

  2. Seed fennel outdoors

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

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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.

Rock County, Nebraska is in USDA Zone 5a. The average last spring frost is May 10 and the first fall frost is October 6, giving you a growing season of approximately 149 days.

At an elevation of 1,012 feet, Rock County receives approximately 32.4 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Fennel to ensure they mature before fall.

Rock County, NE (Zone 5a) Short season
149 days
Last Spring Frost May 10
149 growing days
First Fall Frost October 6

Rock County Soil Profile

Soil Type

Loam

Soil pH

6.7-7.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (31 days to spare)
Start indoors: Mar 6 Transplant: May 15 🍅 Harvest: Jul 17 – Aug 28
Recommended (50%) ✓ Fits season (30 days to spare)
Start indoors: Mar 15 Transplant: May 24 🍅 Harvest: Jul 26 – Sep 6
Safe Start (90%) ✓ Fits season (30 days to spare)
Start indoors: Mar 27 Transplant: Jun 5 🍅 Harvest: Aug 7 – Sep 18

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 Rock County

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

Soil pH

Your soil pH (6.7–7.3) overlaps with Fennel's range (5.5–7.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is moderate (3.3%). Annual compost additions will help Fennel.

How to Plant Fennel

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

Succession Planting Fennel

2
successive plantings in your 149-day season

Sow every 6.9 weeks. Last sowing by Jul 08 to harvest before frost.

Plant Water Budget

Plant needs
0.6″/week
Rainfall provides
0.9″/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 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 0.9" 0" ❄️ Dormant
Feb 1.2" 0" ❄️ Dormant
Mar 1.9" 0" ❄️ Dormant
Apr 3.8" 0" ❄️ Dormant
May 2.6" 4.6" 0" ✅ Rainfall sufficient
Jun 2.6" 5.6" 0" ✅ Rainfall sufficient
Jul 2.6" 3.5" 0" ✅ Rainfall sufficient
Aug 2.6" 4" 0" ✅ Rainfall sufficient
Sep 2.6" 3.2" 0" ✅ Rainfall sufficient
Oct 2.6" 1.8" 0.8" 💧 Light watering
Nov 1.1" 0" ❄️ Dormant
Dec 0.8" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Rock 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 ~806 GDD — county provides 1,601 GDD Excellent fit

Fennel Planting Timeline — Rock County, NE

Fennel Planting Calendar

Activity When Date Range
Start Indoors March 15 Mar 15 – Mar 29
Transplant Outdoors May 24 May 24 – Jun 7
Direct Sow May 17 May 17 – Jun 7
Harvest July 26 Jul 26 – Sep 6

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 Transplant Outdoors Direct Sow
July Harvest
August Harvest
September Harvest
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: acceptable

🗺️ USDA Zone

Zone 5a

📆 Growing Season

149 days in Rock County

Growing Tips for Fennel in Rock County

Direct sow Fennel outdoors after May 10 in Rock 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 Rock County, NE?

Rock County is in Zone 5a with an average last frost of May 10. Plan your Fennel planting based on this frost date — see the calendar above for exact timing.

What planting zone is Rock County, NE?

Rock County, Nebraska is in USDA Hardiness Zone 5a. The average last spring frost is May 10 and first fall frost is October 6.

🌱

Your Rock County Garden Planner — Free

A 24-page printable planner built for Rock 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 Rock County, NE. 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.