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When to Plant Ageratum in Thomas County, NE

Thomas County, Nebraska Zone 5b June

June in the garden — Thomas County, Nebraska

Your garden in Thomas County, Nebraska is working on a schedule, even when you're not. Here's where you should be this June.

Avg. last frost May 10
Avg. first frost October 5
Soil temp (4") 64°F
Watering High
Pest pressure High
Daylight 15 hrs
  1. Start ageratum indoors

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

Coming up in July — start thinking about
  • 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.

Thomas County, Nebraska is in USDA Zone 5b. The average last spring frost is May 10 and the first fall frost is October 5, giving you a growing season of approximately 148 days.

At an elevation of 1,062 feet, Thomas County receives approximately 31.2 inches of rainfall annually with predominantly 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
Thomas County, NE (Zone 5b) Short season
148 days
Last Spring Frost May 10
148 growing days
First Fall Frost October 5

Thomas County Soil Profile

Soil Type

Loam

Soil pH

6.2-7.4

Drainage

Well Drained

Ageratum Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 16 Transplant: May 11 🌸 Bloom: Jul 6 – Oct 5
Recommended (50%) ✗ May not fit
Start indoors: Mar 22 Transplant: May 17 🌸 Bloom: Jul 12 – Oct 11
Safe Start (90%) ✗ May not fit
Start indoors: Apr 3 Transplant: May 29 🌸 Bloom: Jul 24 – Oct 23

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 Thomas County

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

Soil pH

Your soil pH (6.2–7.4) overlaps with Ageratum's range (6.0–7.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is moderate (3.6%). Annual compost additions will help Ageratum.

How to Plant Ageratum

8"
Between Plants
10"
Between Rows

Succession Planting Ageratum

2
successive plantings in your 148-day season

Sow every 6.9 weeks. Last sowing by Jul 22 to harvest before frost.

Ageratum Water Budget

Plant needs
1.0″/week
Rainfall provides
0.9″/week
You supply
0.1″/week
Watering frequency Only during dry spells
Season total 181 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 2" 0" ❄️ Dormant
Feb 1.8" 0" ❄️ Dormant
Mar 3" 0" ❄️ Dormant
Apr 3.1" 0" ❄️ Dormant
May 4.3" 3.3" 1" 💧 Light watering
Jun 4.3" 2.1" 2.2" 🚿 Regular watering
Jul 4.3" 2.9" 1.4" 💧 Light watering
Aug 4.3" 3.8" 0.5" 💧 Light watering
Sep 4.3" 2.4" 1.9" 💧 Light watering
Oct 4.3" 2.5" 1.8" 💧 Light watering
Nov 2.6" 0" ❄️ Dormant
Dec 1.8" 0" ❄️ Dormant

Water needs are for active growing months only (May–Oct in Thomas 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 1,924 GDD Excellent fit

Ageratum Planting Timeline — Thomas County, NE

Ageratum Planting Calendar

Activity When Date Range
Start Indoors March 22 Mar 22 – Apr 5
Transplant Outdoors May 17 May 17 – May 31
Direct Sow May 17 May 17 – Jun 7
Bloom July 12 Jul 12 – Oct 11

· 8" apart · Rows 10" apart

Month-by-Month Timeline

MonthActivities
January
February
March Start Indoors
April Start Indoors
May Transplant Outdoors Direct Sow
June Direct Sow
July Bloom
August Bloom
September Bloom
October Bloom
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 5b

📆 Growing Season

148 days in Thomas County

Growing Tips for Ageratum in Thomas County

Direct sow Ageratum outdoors after May 10 in Thomas 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 Thomas County, NE?

Thomas County is in Zone 5b with an average last frost of May 10. Plan your Ageratum planting based on this frost date — see the calendar above for exact timing.

What planting zone is Thomas County, NE?

Thomas County, Nebraska is in USDA Hardiness Zone 5b. The average last spring frost is May 10 and first fall frost is October 5.

🌱

Your Thomas County Garden Planner — Free

A 22-page printable planner built for Thomas 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 Thomas County, NE. Local conditions may vary. Last updated: June 2026.

Sources & credits

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