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When to Plant Impatiens in Forest County, WI

Forest County, Wisconsin Zone 4b June

Top priorities for Forest County, Wisconsin gardeners in June

A quick June briefing for Forest County, Wisconsin gardeners — what's urgent, what's next, and what can wait.

Avg. last frost May 20
Avg. first frost September 30
Soil temp (4") 64°F
Watering Low
Pest pressure High
Daylight 15.5 hrs
  1. Plant out impatiens

    Plant tomatoes deep — bury the stem up to the first true leaves to grow extra roots. Everything else goes in at the same depth it grew in the tray.

Looking ahead to July
  • Starting indoors: impatiens

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Impatiens (Impatiens walleriana) are the go-to annual for shaded beds and containers. They produce a continuous carpet of flat-faced blooms from transplant until frost, needing little deadheading. Their preference for consistent moisture and part-shade makes them ideal under trees and along north-facing borders.

Forest County, Wisconsin is in USDA Zone 4b. The average last spring frost is May 20 and the first fall frost is September 30, giving you a growing season of approximately 133 days.

At an elevation of 556 feet, Forest County receives approximately 34.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Impatiens to ensure they mature before fall.

Annual Blooms in Summer Pollinator-friendly
Forest County, WI (Zone 4b) Short season
133 days
Last Spring Frost May 20
133 growing days
First Fall Frost September 30
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Forest County Soil Profile

Soil Type

Silt Loam

Soil pH

5.8-6.7

Drainage

Well Drained

Impatiens Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 13 Transplant: May 29 🌸 Bloom: Aug 14 – Oct 16
Recommended (50%) ✗ May not fit
Start indoors: Mar 18 Transplant: Jun 3 🌸 Bloom: Aug 19 – Oct 21
Safe Start (90%) ✗ May not fit
Start indoors: Mar 29 Transplant: Jun 14 🌸 Bloom: Aug 30 – Nov 1

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 Forest County

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

Soil pH

Your soil pH (5.8–6.7) overlaps with Impatiens's range (6.0–6.5), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is excellent (4.2%) — Impatiens will thrive.

How to Plant Impatiens

10"
Between Plants
12"
Between Rows

Succession Planting Impatiens

2
successive plantings in your 133-day season

Sow every 6.9 weeks. Last sowing by Jul 17 to harvest before frost.

Impatiens Water Budget

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

Monthly Watering Guide for Impatiens

Impatiens needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Impatiens Needs Rainfall You Supplement Action
Jan 1.2" 0" ❄️ Dormant
Feb 1.4" 0" ❄️ Dormant
Mar 2.3" 0" ❄️ Dormant
Apr 3.1" 0" ❄️ Dormant
May 4.3" 4" 0.3" 💧 Light watering
Jun 4.3" 4.1" 0.2" 💧 Light watering
Jul 4.3" 3.6" 0.7" 💧 Light watering
Aug 4.3" 4.1" 0.2" 💧 Light watering
Sep 4.3" 3.4" 0.9" 💧 Light watering
Oct 2.5" 0" ❄️ Dormant
Nov 2.4" 0" ❄️ Dormant
Dec 2.1" 0" ❄️ Dormant

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

Impatiens 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.

Impatiens needs ~827 GDD — county provides 1,629 GDD Excellent fit

Impatiens Planting Timeline — Forest County, WI

Impatiens Planting Calendar

Activity When Date Range
Start Indoors March 18 Mar 18 – Apr 1
Transplant Outdoors June 3 Jun 3 – Jun 17
Bloom August 19 Aug 19 – Oct 21

· 10" apart · Rows 12" apart

Month-by-Month Timeline

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

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

1"/week · Natural rainfall sufficient

📅 Days to Maturity

60–75 days

🧪 Soil pH

Needs 6–6.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 4b

📆 Growing Season

133 days in Forest County

Growing Tips for Impatiens in Forest County

Direct sow Impatiens outdoors after May 20 in Forest County when soil has warmed and frost danger has passed.

General growing tips

Start seeds indoors 8–10 weeks before last frost at 70–75°F; germination requires light — do not cover seeds. Transplant after last frost once nights consistently exceed 50°F. Water regularly — wilting causes bud drop and they rarely fully recover the same flush. Watch for impatiens downy mildew (IDM); consider New Guinea impatiens as a resistant alternative in affected regions. Pinch tips at planting to encourage branching.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Impatiens in Forest County, WI?

Forest County is in Zone 4b with an average last frost of May 20. Plan your Impatiens planting based on this frost date — see the calendar above for exact timing.

What planting zone is Forest County, WI?

Forest County, Wisconsin is in USDA Hardiness Zone 4b. The average last spring frost is May 20 and first fall frost is September 30.

🌱

Your Forest County Garden Planner — Free

A 22-page printable planner built for Forest County (Zone 4b). 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 Forest County, WI. Local conditions may vary. Last updated: June 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.