Blog

When to Plant Ageratum in Montgomery County, TX

Montgomery County, Texas Zone 9a June

Your June planting checklist for Montgomery County, Texas

A quick June briefing for Montgomery County, Texas gardeners — what's urgent, what's next, and what can wait.

Avg. last frost February 18
Avg. first frost December 1
Soil temp (4") 84°F
Watering Low
Pest pressure High
Daylight 13.9 hrs
  1. Bring in the ageratum

    Check every 1–2 days. Many of these get tough or go to seed if you wait too long.

Get ahead of July
  • First harvests: ageratum

Instant PDF download. No spam, unsubscribe any time.

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.

Montgomery County, Texas is in USDA Zone 9a. The average last spring frost is February 18 and the first fall frost is December 1, giving you a growing season of approximately 286 days.

At an elevation of 180 feet, Montgomery County receives approximately 62.1 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 96°F, so Ageratum may need afternoon shade and extra watering during peak heat. Sandy soil warms quickly in spring — great for early planting — but Ageratum will need more frequent watering and organic matter to retain nutrients. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Ageratum root diseases.

Annual Blooms in Multi-season Pollinator-friendly Good for cutting
Montgomery County, TX (Zone 9a) Year-round
286 days
Last Spring Frost February 18
286 growing days
First Fall Frost December 1

Montgomery County Soil Profile

Soil Type

Sandy Loam

Soil pH

5.5-6.7

Drainage

Well Drained

Ageratum Planting Risk Windows

Early Start (70% safe) ✓ Fits season (77 days to spare)
Start indoors: Dec 30 Transplant: Jan 27 🌸 Bloom: Mar 24 – Sep 8
Recommended (50%) ✓ Fits season (76 days to spare)
Start indoors: Jan 7 Transplant: Feb 4 🌸 Bloom: Apr 1 – Sep 16
Safe Start (90%) ✓ Fits season (73 days to spare)
Start indoors: Jan 26 Transplant: Feb 23 🌸 Bloom: Apr 20 – Oct 5

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 Montgomery County

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

Soil pH

Your soil pH (5.5–6.7) overlaps with Ageratum's range (6.0–7.0), though not a perfect match.

Soil Texture

Sandy soil in Montgomery County warms quickly in spring but drains fast. Ageratum will need more frequent watering and regular compost additions to retain nutrients.

Organic Matter

Organic matter is low (1.8%). Add 2-3 inches of compost before planting Ageratum.

How to Plant Ageratum

8"
Between Plants
10"
Between Rows

Succession Planting Ageratum

5
successive plantings in your 286-day season

Sow every 6.9 weeks. Last sowing by Sep 17 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 233 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 4.3" 2.1" 2.2" 🚿 Regular watering
Mar 4.3" 4.5" 0" ✅ Rainfall sufficient
Apr 4.3" 6.5" 0" ✅ Rainfall sufficient
May 4.3" 8.2" 0" ✅ Rainfall sufficient
Jun 4.3" 11" 0" ✅ Rainfall sufficient
Jul 4.3" 8" 0" ✅ Rainfall sufficient
Aug 4.3" 7.1" 0" ✅ Rainfall sufficient
Sep 4.3" 5.3" 0" ✅ Rainfall sufficient
Oct 4.3" 4.2" 0.1" 💧 Light watering
Nov 4.3" 2" 2.3" 🚿 Regular watering
Dec 4.3" 1.6" 2.7" 🚿 Regular watering

Water needs are for active growing months only (Feb–Dec in Montgomery 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 ~1,485 GDD — county provides 6,314 GDD Excellent fit

Ageratum Planting Timeline — Montgomery County, TX

Ageratum Planting Calendar

Activity When Date Range
Start Indoors January 7 Jan 7 – Jan 21
Transplant Outdoors February 4 Feb 4 – Feb 18
Direct Sow February 4 Feb 4 – Feb 25
Bloom April 1 Apr 1 – Sep 16

· 8" apart · Rows 10" apart

Month-by-Month Timeline

MonthActivities
January Start Indoors
February Transplant Outdoors Direct Sow
March
April Bloom
May Bloom
June Bloom
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 9a

📆 Growing Season

286 days in Montgomery County

Growing Tips for Ageratum in Montgomery County

Direct sow Ageratum outdoors after February 18 in Montgomery County when soil has warmed and frost danger has passed.

Sandy soil in Montgomery County dries quickly — mulch Ageratum with 2-3 inches of straw and water deeply 2-3 times per week rather than lightly every day.

With summer highs reaching 96°F in Montgomery County, provide afternoon shade for Ageratum and water deeply in the morning.

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 Montgomery County, TX?

Montgomery County is in Zone 9a with an average last frost of February 18. Plan your Ageratum planting based on this frost date — see the calendar above for exact timing.

What planting zone is Montgomery County, TX?

Montgomery County, Texas is in USDA Hardiness Zone 9a. The average last spring frost is February 18 and first fall frost is December 1.

🌱

Your Montgomery County Garden Planner — Free

A 22-page printable planner built for Montgomery County (Zone 9a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

Instant PDF download. No spam, unsubscribe any time.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Montgomery County, TX. 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.