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When to plant Ageratum in Monroe County County,

Aim to plant Ageratum in Monroe County County on or after April 27; the window stays open through May 18. Monroe County County's 173-day frost-free season gives you a single solid spring crop with a brief fall option.

When to Plant Ageratum in Monroe County, MI

Monroe County, Michigan Zone 6b June

June in Monroe County, Michigan — your action list

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

Avg. last frost April 27
Avg. first frost October 17
Soil temp (4") 74°F
Watering Low
Pest pressure High
Daylight 15 hrs
  1. Indoor seed-starting week for ageratum

    Give them 6–8 weeks indoors before the last frost and you'll transplant into warm soil with seedlings that are already leaping.

  2. Bring in the ageratum

    Don't tug. Use scissors or pruners for clean cuts — torn stems invite disease.

July prep starts now
  • 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.

Monroe County, Michigan is in USDA Zone 6b. The average last spring frost is April 27 and the first fall frost is October 17, giving you a growing season of approximately 173 days.

At an elevation of 1,202 feet, Monroe County receives approximately 40.6 inches of rainfall annually with predominantly silt loam soil. Summer highs average 89°F, providing good warmth for Ageratum during the growing season.

Annual Blooms in Multi-season Pollinator-friendly Good for cutting
Monroe County, MI (Zone 6b) Moderate season
173 days
Last Spring Frost April 27
173 growing days
First Fall Frost October 17
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Monroe County Soil Profile

Soil Type

Silt Loam

Soil pH

5.8-7.2

Drainage

Well Drained

Ageratum Planting Risk Windows

Early Start (70% safe) ✓ Fits season (8 days to spare)
Start indoors: Mar 6 Transplant: Apr 24 🌸 Bloom: Jun 19 – Oct 2
Recommended (50%) ✓ Fits season (12 days to spare)
Start indoors: Mar 9 Transplant: Apr 27 🌸 Bloom: Jun 22 – Oct 5
Safe Start (90%) ✓ Fits season (9 days to spare)
Start indoors: Mar 25 Transplant: May 13 🌸 Bloom: Jul 8 – Oct 21

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 Monroe County

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

Soil pH

Your soil pH (5.8–7.2) overlaps with Ageratum's range (6.0–7.0), though not a perfect match.

Soil Texture

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

Drainage

Drainage is adequate for Ageratum.

Organic Matter

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

How to Plant Ageratum

8"
Between Plants
10"
Between Rows

Succession Planting Ageratum

3
successive plantings in your 173-day season

Sow every 6.9 weeks. Last sowing by Aug 03 to harvest before frost.

Ageratum Water Budget

Plant needs
1.0″/week
Rainfall provides
1.0″/week
You supply
0.3″/week
Watering frequency 1-2 times/week
Season total 484 gal / 100 sq ft

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 1.6" 0" ❄️ Dormant
Feb 1.9" 0" ❄️ Dormant
Mar 3.1" 0" ❄️ Dormant
Apr 4.3" 3.5" 0.8" 💧 Light watering
May 4.3" 4.7" 0" ✅ Rainfall sufficient
Jun 4.3" 5.6" 0" ✅ Rainfall sufficient
Jul 4.3" 4.3" 0" ✅ Rainfall sufficient
Aug 4.3" 4.5" 0" ✅ Rainfall sufficient
Sep 4.3" 3.3" 1" 💧 Light watering
Oct 4.3" 3.5" 0.8" 💧 Light watering
Nov 2.6" 0" ❄️ Dormant
Dec 2" 0" ❄️ Dormant

Water needs are for active growing months only (Apr–Oct in Monroe 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 ~1,131 GDD — county provides 2,897 GDD Excellent fit

Ageratum Planting Timeline — Monroe County, MI

Ageratum Planting Calendar

Activity When Date Range
Start Indoors March 9 Mar 9 – Mar 23
Transplant Outdoors April 27 Apr 27 – May 11
Direct Sow April 27 Apr 27 – May 18
Bloom June 22 Jun 22 – Oct 5

· 8" apart · Rows 10" apart

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · 1-2 times/week

📅 Days to Maturity

60–75 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 6b

📆 Growing Season

173 days in Monroe County

Growing Tips for Ageratum in Monroe County

Direct sow Ageratum outdoors after April 27 in Monroe 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 Monroe County, MI?

Monroe County is in Zone 6b with an average last frost of April 27. Plan your Ageratum planting based on this frost date — see the calendar above for exact timing.

What planting zone is Monroe County, MI?

Monroe County, Michigan is in USDA Hardiness Zone 6b. The average last spring frost is April 27 and first fall frost is October 17.

When should I plant Ageratum in Monroe County, ?

In Monroe County, , plant Ageratum after the last frost (around April 27) and before the first frost (around October 17). Best results when soil holds above 50°F.

What growing zone is Monroe County, for Ageratum?

Monroe County sits in USDA Zone 6b. Ageratum grows reliably in zones 3a through 11b, so it's a good fit here.

Can Ageratum grow in Monroe County's climate?

Yes — Ageratum grows well in Monroe County's temperate climate. Monroe County averages a 173-day frost-free season, with last frost around April 27 and first frost around October 17.

🌱

Your Monroe County Garden Planner — Free

A 22-page printable planner built for Monroe County (Zone 6b). 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 Monroe County, MI. 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.