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When to Plant Ageratum in Rolette County, ND

Rolette County, North Dakota Zone 3b June

Your June planting checklist for Rolette County, North Dakota

Each item below is timed to Rolette County, North Dakota's frost dates and soil temperatures. Skip nothing, stress about nothing.

Avg. last frost May 17
Avg. first frost September 22
Soil temp (4") 61°F
Watering Low
Pest pressure Moderate
Daylight 15.9 hrs
Before July arrives, get these ready
  • Starting indoors: ageratum
  • First harvests: ageratum

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Ageratum (Ageratum houstonianum), the floss flower, produces clusters of fluffy, powder-puff blooms in the rare sky-blue and lavender tones difficult to find among warm-season annuals. Compact mounding habit makes it ideal as a front-of-border edging plant. Blooms from early summer through fall with minimal deadheading; heat and humidity tolerant once established.

Rolette County, North Dakota is in USDA Zone 3b. The average last spring frost is May 17 and the first fall frost is September 22, giving you a growing season of approximately 128 days.

At an elevation of 998 feet, Rolette County receives approximately 31.8 inches of rainfall annually with predominantly loam soil. Summer highs average 78°F, so choose short-season varieties of Ageratum to ensure they mature before fall.

Annual Blooms in Multi-season Pollinator-friendly Good for cutting
Rolette County, ND (Zone 3b) Short season
128 days
Last Spring Frost May 17
128 growing days
First Fall Frost September 22

Rolette County Soil Profile

Soil Type

Loam

Soil pH

6.5-7.8

Drainage

Well Drained

Ageratum Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 16 Transplant: May 25 🌸 Bloom: Jul 20 – Sep 21
Recommended (50%) ✗ May not fit
Start indoors: Mar 22 Transplant: May 31 🌸 Bloom: Jul 26 – Sep 27
Safe Start (90%) ✗ May not fit
Start indoors: Apr 2 Transplant: Jun 11 🌸 Bloom: Aug 6 – Oct 8

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 Rolette County

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

Soil pH

Your soil pH (6.5–7.8) is more alkaline than Ageratum prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (3.8%). Annual compost additions will help Ageratum.

How to Plant Ageratum

8"
Between Plants
10"
Between Rows

Succession Planting Ageratum

2
successive plantings in your 128-day season

Sow every 6.9 weeks. Last sowing by Jul 09 to harvest before frost.

Ageratum Water Budget

Plant needs
1.0″/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 Ageratum

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

Month Ageratum Needs Rainfall You Supplement Action
Jan 0.8" 0" ❄️ Dormant
Feb 1.3" 0" ❄️ Dormant
Mar 2.3" 0" ❄️ Dormant
Apr 3.5" 0" ❄️ Dormant
May 4.3" 4.4" 0" ✅ Rainfall sufficient
Jun 4.3" 5" 0" ✅ Rainfall sufficient
Jul 4.3" 4.3" 0" ✅ Rainfall sufficient
Aug 4.3" 3.7" 0.6" 💧 Light watering
Sep 4.3" 2.8" 1.5" 💧 Light watering
Oct 2.1" 0" ❄️ Dormant
Nov 0.9" 0" ❄️ Dormant
Dec 0.7" 0" ❄️ Dormant

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

Ageratum 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.

Ageratum needs ~574 GDD — county provides 1,088 GDD Excellent fit

Ageratum Planting Timeline — Rolette County, ND

Ageratum Planting Calendar

Activity When Date Range
Start Indoors March 22 Mar 22 – Apr 5
Transplant Outdoors May 31 May 31 – Jun 14
Direct Sow May 31 May 31 – Jun 21
Bloom July 26 Jul 26 – Sep 27

· 8" apart · Rows 10" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Natural rainfall sufficient

📅 Days to Maturity

60–75 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 3b

📆 Growing Season

128 days in Rolette County

Growing Tips for Ageratum in Rolette County

Direct sow Ageratum outdoors after May 17 in Rolette County when soil has warmed and frost danger has passed.

Common pests for Ageratum in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.

General growing tips

Start seeds indoors 6–8 weeks before last frost — do not cover seed; it needs light to germinate. Can be direct-sown after last frost once soil warms to 60°F. Transplant or thin to proper spacing after frost danger passes. Deadheading isn't strictly required but tidying spent clusters improves appearance. Provide consistent moisture; drought causes premature setting. Avoid deep shade — blooms best in full sun to light afternoon shade.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Ageratum in Rolette County, ND?

Rolette County is in Zone 3b with an average last frost of May 17. Plan your Ageratum planting based on this frost date — see the calendar above for exact timing.

What planting zone is Rolette County, ND?

Rolette County, North Dakota is in USDA Hardiness Zone 3b. The average last spring frost is May 17 and first fall frost is September 22.

🌱

Your Rolette County Garden Planner — Free

A 22-page printable planner built for Rolette County (Zone 3b). 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 Rolette County, ND. 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.