Blog

When to Plant Rue in Iron County, WI

Iron County, Wisconsin Zone 4a May

Top priorities for Iron County, Wisconsin gardeners in May

If you only do a handful of things in the garden this May, make it these. They're sequenced around your zone's frost timing.

Avg. last frost May 22
Avg. first frost September 25
Soil temp (4") 50°F
Watering Moderate
Pest pressure Low
Daylight 14.8 hrs
  1. Move rue into the garden

    Bring a watering can to the bed. Each transplant gets a drink the moment it's in the ground, not ten minutes later.

Instant PDF download. No spam, unsubscribe any time.

Rue is a bitter, aromatic perennial herb with bluish-green foliage used historically in medicine and as a pest deterrent. Handle with care as its sap can cause skin irritation.

Iron County, Wisconsin is in USDA Zone 4a. The average last spring frost is May 22 and the first fall frost is September 25, giving you a growing season of approximately 126 days.

At an elevation of 841 feet, Iron County receives approximately 32.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 78°F, so choose short-season varieties of Rue to ensure they mature before fall.

Iron County, WI (Zone 4a) Short season
126 days
Last Spring Frost May 22
126 growing days
First Fall Frost September 25

Iron County Soil Profile

Soil Type

Silt Loam

Soil pH

5.7-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Transplant: May 25 🍅 Harvest: Aug 3 – Oct 5
Recommended (50%) ✗ May not fit
Transplant: May 29 🍅 Harvest: Aug 7 – Oct 9
Safe Start (90%) ✗ May not fit
Transplant: Jun 13 🍅 Harvest: Aug 22 – Oct 24

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 Iron County

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

Soil pH

Your soil pH (5.7–6.9) overlaps with Rue's range (6.0–7.5), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is excellent (4.6%) — Rue will thrive.

How to Plant Rue

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

Succession Planting Rue

2
successive plantings in your 126-day season

Sow every 8 weeks. Last sowing by Jun 27 to harvest before frost.

Plant Water Budget

Plant needs
0.5″/week
Rainfall provides
1.1″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft

Monthly Watering Guide for Rue

Rue needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.

Month Rue Needs Rainfall You Supplement Action
Jan 1.2" 0" ❄️ Dormant
Feb 1.4" 0" ❄️ Dormant
Mar 2.4" 0" ❄️ Dormant
Apr 3" 0" ❄️ Dormant
May 2.2" 3.7" 0" ✅ Rainfall sufficient
Jun 2.2" 3.6" 0" ✅ Rainfall sufficient
Jul 2.2" 3.6" 0" ✅ Rainfall sufficient
Aug 2.2" 3.7" 0" ✅ Rainfall sufficient
Sep 2.2" 3.2" 0" ✅ Rainfall sufficient
Oct 2.5" 0" ❄️ Dormant
Nov 2.3" 0" ❄️ Dormant
Dec 1.8" 0" ❄️ Dormant

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

Rue 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.

Rue needs ~680 GDD — county provides 1,071 GDD Excellent fit

Rue Planting Timeline — Iron County, WI

Rue Planting Calendar

Activity When Date Range
Transplant Outdoors May 29 May 29 – Jun 12
Harvest August 7 Aug 7 – Oct 9

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.5"/week · Natural rainfall sufficient

📅 Days to Maturity

70–90 days

🧪 Soil pH

Needs 6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 4a

📆 Growing Season

126 days in Iron County

Growing Tips for Rue in Iron County

Direct sow Rue outdoors after May 22 in Iron County when soil has warmed and frost danger has passed.

General growing tips

Start seeds indoors or direct sow. Plant in well-drained soil. Wear gloves when handling as sap can cause phytophotodermatitis. Prune in early spring.

Companion Planting

Good Companions

Avoid Planting Near

  • Basil
  • Sage

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Rue in Iron County, WI?

Iron County is in Zone 4a with an average last frost of May 22. Plan your Rue planting based on this frost date — see the calendar above for exact timing.

What planting zone is Iron County, WI?

Iron County, Wisconsin is in USDA Hardiness Zone 4a. The average last spring frost is May 22 and first fall frost is September 25.

🌱

Your Iron County Garden Planner — Free

A 24-page printable planner built for Iron County (Zone 4a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

Instant PDF download. No spam, unsubscribe any time.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Iron County, WI. 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.