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When to Plant Broccoli Rabe in Poweshiek County, IA

Poweshiek County, Iowa Zone 5b May

This month in Poweshiek County, Iowa

Your garden in Poweshiek County, Iowa is working on a schedule, even when you're not. Here's where you should be this May.

Avg. last frost May 2
Avg. first frost October 7
Soil temp (4") 58°F
Watering Low
Pest pressure Low
Daylight 14.4 hrs
  1. Set out broccoli rabe seedlings

    Your last frost (May 2) has passed. These warm-season crops can handle outdoor soil now.

Looking ahead to June
  • Starting indoors: broccoli rabe
  • First harvests: broccoli rabe

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Broccoli rabe (rapini) is a brassica grown for its slightly bitter, nutty-flavored florets, leaves, and stems. It is a staple in Italian cooking.

Poweshiek County, Iowa is in USDA Zone 5b. The average last spring frost is May 2 and the first fall frost is October 7, giving you a growing season of approximately 158 days.

At an elevation of 1,221 feet, Poweshiek County receives approximately 36 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Broccoli Rabe during the growing season.

Poweshiek County, IA (Zone 5b) Moderate season
158 days
Last Spring Frost May 2
158 growing days
First Fall Frost October 7
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Poweshiek County Soil Profile

Soil Type

Silt Loam

Soil pH

5.9-6.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (85 days to spare)
Start indoors: Mar 18 Transplant: Apr 22 🍅 Harvest: Jun 3 – Jul 8
Recommended (50%) ✓ Fits season (81 days to spare)
Start indoors: Mar 28 Transplant: May 2 🍅 Harvest: Jun 13 – Jul 18
Safe Start (90%) ✓ Fits season (77 days to spare)
Start indoors: Apr 10 Transplant: May 15 🍅 Harvest: Jun 26 – Jul 31

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 Poweshiek County

How your county's soil matches Broccoli Rabe's growing requirements.

Soil pH

Your soil pH (5.9–6.8) overlaps with Broccoli Rabe's range (6.0–7.5), though not a perfect match.

Soil Texture

The silt loam soil in Poweshiek County is excellent for Broccoli Rabe — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is excellent (4.5%) — Broccoli Rabe will thrive.

How to Plant Broccoli Rabe

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

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Succession Planting Broccoli Rabe

4
successive plantings in your 158-day season

Sow every 4.6 weeks. Last sowing by Aug 08 to harvest before frost.

For a dedicated fall crop, sow by Jul 29.

Plant Water Budget

Plant needs
0.8″/week
Rainfall provides
1.0″/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 Broccoli Rabe

Broccoli Rabe 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 Broccoli Rabe Needs Rainfall You Supplement Action
Jan 1.4" 0" ❄️ Dormant
Feb 1.8" 0" ❄️ Dormant
Mar 2.6" 0" ❄️ Dormant
Apr 3.7" 0" ❄️ Dormant
May 3.5" 4.1" 0" ✅ Rainfall sufficient
Jun 3.5" 4.8" 0" ✅ Rainfall sufficient
Jul 3.5" 3.4" 0.1" 💧 Light watering
Aug 3.5" 3.7" 0" ✅ Rainfall sufficient
Sep 3.5" 2.8" 0.7" 💧 Light watering
Oct 3.5" 3" 0.5" 💧 Light watering
Nov 2.7" 0" ❄️ Dormant
Dec 1.9" 0" ❄️ Dormant

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

Broccoli Rabe 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.

Broccoli Rabe needs ~725 GDD — county provides 2,291 GDD Excellent fit

Broccoli Rabe Planting Timeline — Poweshiek County, IA

Broccoli Rabe Planting Calendar

Activity When Date Range
Start Indoors March 28 Mar 28 – Apr 11
Transplant Outdoors May 2 May 2 – May 16
Direct Sow April 18 Apr 18 – May 9
Harvest June 13 Jun 13 – Jul 18
Fall Sowing July 29 Jul 29 – Aug 12

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

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.8"/week · Natural rainfall sufficient

📅 Days to Maturity

40–60 days

🧪 Soil pH

Needs 6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 5b

📆 Growing Season

158 days in Poweshiek County

Growing Tips for Broccoli Rabe in Poweshiek County

Direct sow Broccoli Rabe outdoors after May 02 in Poweshiek County when soil has warmed and frost danger has passed.

Your generous 158.0-day season in Poweshiek County allows multiple plantings of Broccoli Rabe. Sow every 20.0 days for continuous harvest.

Common pests for Broccoli Rabe in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow in spring or fall. Harvest when small yellow flower buds first appear but before they open. Cut the main shoot first to encourage side shoots.

Companion Planting

Good Companions

Avoid Planting Near

  • Strawberries

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Broccoli Rabe in Poweshiek County, IA?

Poweshiek County is in Zone 5b with an average last frost of May 2. Plan your Broccoli Rabe planting based on this frost date — see the calendar above for exact timing.

What planting zone is Poweshiek County, IA?

Poweshiek County, Iowa is in USDA Hardiness Zone 5b. The average last spring frost is May 2 and first fall frost is October 7.

🌱

Your Poweshiek County Garden Planner — Free

A 24-page printable planner built for Poweshiek County (Zone 5b). 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 Poweshiek County, IA. 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.