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When to plant Ageratum in Au Gres, MI

Au Gres's 147-day season only supports one Ageratum planting per year. Sow between May 19 and June 9 for the best chance at full maturity before October 6.

When to Plant Ageratum in Au Gres, MI

Arenac County, Michigan Zone 5b July

Arenac County, Michigan gardeners: here's your July plan

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

Avg. last frost May 12
Avg. first frost October 6
Soil temp (4") 78°F
Watering Moderate
Pest pressure High
Daylight 15 hrs
  1. Basket week: ageratum

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

A few tasks this July that'll pay off in August
  • 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.

Au Gres, Michigan is in USDA Zone 5b. The average last spring frost is May 12 and the first fall frost is October 6, giving you a growing season of approximately 147 days.

At an elevation of 1,015 feet, Arenac County receives approximately 30.5 inches of rainfall annually with predominantly silt loam soil. Summer highs average 86°F, providing good warmth for Ageratum during the growing season.

Annual Blooms in Multi-season Pollinator-friendly Good for cutting
Au Gres, MI (Zone 5b) Short season
147 days
Last Spring Frost May 12
147 growing days
First Fall Frost October 6

Au Gres Soil Profile

Soil Type

Silt Loam

Soil pH

6.2-7.1

Drainage

Well Drained

Ageratum Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 18 Transplant: May 13 🌸 Bloom: Jul 8 – Oct 7
Recommended (50%) ✗ May not fit
Start indoors: Mar 24 Transplant: May 19 🌸 Bloom: Jul 14 – Oct 13
Safe Start (90%) ✗ May not fit
Start indoors: Apr 6 Transplant: Jun 1 🌸 Bloom: Jul 27 – Oct 26

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 Au Gres

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

Soil pH

Your soil pH (6.2–7.1) overlaps with Ageratum's range (6.0–7.0), though not a perfect match.

Soil Texture

The silt loam soil in Arenac 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 (4.6%) — Ageratum will thrive.

How to Plant Ageratum

8"
Between Plants
10"
Between Rows

Succession Planting Ageratum

2
successive plantings in your 147-day season

Sow every 6.9 weeks. Last sowing by Jul 23 to harvest before frost.

Ageratum Water Budget

Plant needs
1.0″/week
Rainfall provides
0.9″/week
You supply
0.4″/week
Watering frequency 1-2 times/week
Season total 561 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 1.4" 0" ❄️ Dormant
Feb 1.3" 0" ❄️ Dormant
Mar 2.2" 0" ❄️ Dormant
Apr 2.6" 0" ❄️ Dormant
May 4.3" 3.9" 0.4" 💧 Light watering
Jun 4.3" 3.9" 0.4" 💧 Light watering
Jul 4.3" 3.6" 0.7" 💧 Light watering
Aug 4.3" 3.2" 1.1" 💧 Light watering
Sep 4.3" 2.6" 1.7" 💧 Light watering
Oct 4.3" 2.2" 2.1" 💧 Light watering
Nov 2" 0" ❄️ Dormant
Dec 1.7" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Arenac 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 ~979 GDD — county provides 2,131 GDD Excellent fit

Ageratum Planting Timeline — Au Gres, MI

Ageratum Planting Calendar

Activity When Date Range
Start Indoors March 24 Mar 24 – Apr 7
Transplant Outdoors May 19 May 19 – Jun 2
Direct Sow May 19 May 19 – Jun 9
Bloom July 14 Jul 14 – Oct 13

· 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 Bloom
November
December

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 5b

📆 Growing Season

147 days in Arenac County

Growing Tips for Ageratum in Au Gres

Direct sow Ageratum outdoors after May 12 in Arenac 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 →

When should I plant Ageratum in Au Gres, MI?

In Au Gres, MI, plant Ageratum after the last frost (around May 12) and before the first frost (around October 6). Best results when soil holds above 50°F.

What growing zone is Au Gres, MI for Ageratum?

Au Gres sits in USDA Zone 5b. Ageratum grows reliably in zones 3a through 11b, so it's a good fit here.

Can Ageratum grow in Au Gres's climate?

Yes — Ageratum grows well in Au Gres's temperate climate. Au Gres averages a 147-day frost-free season, with last frost around May 12 and first frost around October 6.

🌱

Your Arenac County Garden Planner — Free

A 22-page printable planner built for Arenac 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 Arenac County, MI. Local conditions may vary. Last updated: July 2026.