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When to plant Ageratum in Mitchell County County,

In Zone 5a (Mitchell County County), direct-sow Ageratum between May 10 and May 31 for spring, after the May 3 last-frost mark.

When to Plant Ageratum in Mitchell County, IA

Mitchell County, Iowa Zone 5a June

Your June planting checklist for Mitchell County, Iowa

We've pulled the most time-sensitive tasks for Mitchell County, Iowa this June and put them front and centre. Tackle them in order.

Avg. last frost May 3
Avg. first frost October 7
Soil temp (4") 67°F
Watering Low
Pest pressure High
Daylight 15.2 hrs
  1. Sow ageratum in trays indoors

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

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

Mitchell County, Iowa is in USDA Zone 5a. The average last spring frost is May 3 and the first fall frost is October 7, giving you a growing season of approximately 157 days.

At an elevation of 506 feet, Mitchell County receives approximately 36.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Ageratum to ensure they mature before fall.

Annual Blooms in Multi-season Pollinator-friendly Good for cutting
Mitchell County, IA (Zone 5a) Moderate season
157 days
Last Spring Frost May 3
157 growing days
First Fall Frost October 7

Mitchell County Soil Profile

Soil Type

Silt Loam

Soil pH

5.9-7.3

Drainage

Well Drained

Ageratum Planting Risk Windows

Early Start (70% safe) ✓ Fits season (8 days to spare)
Start indoors: Mar 9 Transplant: May 4 🌸 Bloom: Jun 29 – Sep 21
Recommended (50%) ✓ Fits season (10 days to spare)
Start indoors: Mar 15 Transplant: May 10 🌸 Bloom: Jul 5 – Sep 27
Safe Start (90%) ✓ Fits season (7 days to spare)
Start indoors: Mar 27 Transplant: May 22 🌸 Bloom: Jul 17 – Oct 9

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 Mitchell County

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

Soil pH

Your soil pH (5.9–7.3) overlaps with Ageratum's range (6.0–7.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is excellent (5.1%) — Ageratum will thrive.

How to Plant Ageratum

8"
Between Plants
10"
Between Rows

Succession Planting Ageratum

3
successive plantings in your 157-day season

Sow every 6.9 weeks. Last sowing by Jul 24 to harvest before frost.

Ageratum Water Budget

Plant needs
1.0″/week
Rainfall provides
1.0″/week
You supply
0.0″/week
Watering frequency Only during dry spells
Season total 48 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 1.5" 0" ❄️ Dormant
Mar 2.7" 0" ❄️ Dormant
Apr 3.3" 0" ❄️ Dormant
May 4.3" 4" 0.3" 💧 Light watering
Jun 4.3" 5.1" 0" ✅ Rainfall sufficient
Jul 4.3" 3.9" 0.4" 💧 Light watering
Aug 4.3" 3.9" 0.4" 💧 Light watering
Sep 4.3" 2.9" 1.4" 💧 Light watering
Oct 4.3" 2.4" 1.9" 💧 Light watering
Nov 2.8" 0" ❄️ Dormant
Dec 2" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Mitchell 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 ~878 GDD — county provides 2,041 GDD Excellent fit

Ageratum Planting Timeline — Mitchell County, IA

Ageratum Planting Calendar

Activity When Date Range
Start Indoors March 15 Mar 15 – Mar 29
Transplant Outdoors May 10 May 10 – May 24
Direct Sow May 10 May 10 – May 31
Bloom July 5 Jul 5 – Sep 27

· 8" apart · Rows 10" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Only during dry spells

📅 Days to Maturity

60–75 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 5a

📆 Growing Season

157 days in Mitchell County

Growing Tips for Ageratum in Mitchell County

Direct sow Ageratum outdoors after May 03 in Mitchell 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 Mitchell County, IA?

Mitchell County is in Zone 5a with an average last frost of May 3. Plan your Ageratum planting based on this frost date — see the calendar above for exact timing.

What planting zone is Mitchell County, IA?

Mitchell County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is May 3 and first fall frost is October 7.

When should I plant Ageratum in Mitchell County, ?

In Mitchell County, , plant Ageratum after the last frost (around May 3) and before the first frost (around October 7). Best results when soil holds above 50°F.

What growing zone is Mitchell County, for Ageratum?

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

Can Ageratum grow in Mitchell County's climate?

Yes — Ageratum grows well in Mitchell County's temperate climate. Mitchell County averages a 157-day frost-free season, with last frost around May 3 and first frost around October 7.

🌱

Your Mitchell County Garden Planner — Free

A 22-page printable planner built for Mitchell County (Zone 5a). 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 Mitchell County, IA. Local conditions may vary. Last updated: June 2026.

Sources & credits

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