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When to Plant Begonias in Comal County, TX

Comal County, Texas Zone 9a August

Your August planting checklist for Comal County, Texas

August is a pivotal month for Comal County, Texas gardens. Focus on these tasks first and you'll set up the rest of the season for success.

Avg. last frost March 6
Avg. first frost November 22
Soil temp (4") 90°F
Watering Low
Pest pressure High
Daylight 13.1 hrs
  1. Bring in the begonias

    The more you pick, the more the plant produces. Letting fruit overripen tells the plant it's time to stop.

September will be here before you know it — start on
  • First harvests: begonias

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Wax begonias (Begonia × semperflorens) are the workhorse shade bedding plant of American horticulture, offering continuous bloom from transplant to hard frost. Bronze or green-leaved varieties perform well from deep shade to full sun (in northern zones) and tolerate summer humidity better than most cool- season flowers. A staple of mass plantings, containers, and window boxes.

Comal County, Texas is in USDA Zone 9a. The average last spring frost is March 6 and the first fall frost is November 22, giving you a growing season of approximately 261 days.

At an elevation of 1,346 feet, Comal County receives approximately 58.6 inches of rainfall annually with predominantly clay soil. Summer highs average 91°F, providing good warmth for Begonias during the growing season. Clay soil retains moisture well for Begonias, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Begonias root diseases.

Annual Blooms in Multi-season Pollinator-friendly Deer-resistant
Comal County, TX (Zone 9a) Long season
261 days
Last Spring Frost March 6
261 growing days
First Fall Frost November 22

Comal County Soil Profile

Soil Type

Clay

Soil pH

6.7-7.7

Drainage

Well Drained

Begonias Planting Risk Windows

Early Start (70% safe) ✓ Fits season (32 days to spare)
Start indoors: Dec 16 Transplant: Feb 3 🌸 Bloom: Apr 14 – Oct 13
Recommended (50%) ✓ Fits season (30 days to spare)
Start indoors: Dec 26 Transplant: Feb 13 🌸 Bloom: Apr 24 – Oct 23
Safe Start (90%) ✓ Fits season (22 days to spare)
Start indoors: Jan 22 Transplant: Mar 12 🌸 Bloom: May 21 – Nov 19

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 Comal County

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

Soil pH

Your soil pH (6.7–7.7) is more alkaline than Begonias prefers (5.5–6.5). Add sulfur or peat moss to lower pH.

Soil Texture

Heavy clay soil (47% clay) in Comal County compacts easily and drains slowly. Amend with compost and avoid working soil when wet.

Drainage

Drainage is adequate for Begonias.

Organic Matter

Organic matter is moderate (3.3%). Annual compost additions will help Begonias.

How to Plant Begonias

8"
Between Plants
10"
Between Rows

Succession Planting Begonias

4
successive plantings in your 261-day season

Sow every 8 weeks. Last sowing by Aug 24 to harvest before frost.

Begonias Water Budget

Plant needs
1.0″/week
Rainfall provides
0.9″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Begonias

Begonias needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Begonias Needs Rainfall You Supplement Action
Jan 1.2" 0" ❄️ Dormant
Feb 2.1" 0" ❄️ Dormant
Mar 4.3" 3.8" 0.5" 💧 Light watering
Apr 4.3" 6.6" 0" ✅ Rainfall sufficient
May 4.3" 9.4" 0" ✅ Rainfall sufficient
Jun 4.3" 9.9" 0" ✅ Rainfall sufficient
Jul 4.3" 6.6" 0" ✅ Rainfall sufficient
Aug 4.3" 6.4" 0" ✅ Rainfall sufficient
Sep 4.3" 4.9" 0" ✅ Rainfall sufficient
Oct 4.3" 3.9" 0.4" 💧 Light watering
Nov 4.3" 2" 2.3" 🚿 Regular watering
Dec 1.6" 0" ❄️ Dormant

Water needs are for active growing months only (Mar–Nov in Comal County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Begonias 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.

Begonias needs ~1,460 GDD — county provides 4,763 GDD Excellent fit

Begonias Planting Timeline — Comal County, TX

Begonias Planting Calendar

Activity When Date Range
Start Indoors December 26 Dec 26 – Jan 9
Transplant Outdoors February 13 Feb 13 – Feb 27
Bloom April 24 Apr 24 – Oct 23

· 8" apart · Rows 10" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

1"/week · Natural rainfall sufficient

📅 Days to Maturity

70–90 days

🧪 Soil pH

Needs 5.5–6.5 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 9a

📆 Growing Season

261 days in Comal County

Growing Tips for Begonias in Comal County

Direct sow Begonias outdoors after March 06 in Comal County when soil has warmed and frost danger has passed.

With Comal County's clay soil (47% clay), work in 3-4 inches of compost before planting Begonias. Avoid tilling when soil is wet to prevent compaction.

General growing tips

Start seeds indoors 10–12 weeks before last frost — seed is dust-fine; surface-sow on moist mix under lights, do not cover. Bottom heat (70–75°F) speeds germination. Transplant after frost; begonias are not direct-sown in practice. Pinch seedlings once for branching. Keep soil evenly moist; avoid waterlogged conditions. Bronze-leaf types tolerate more sun; green- leaf types prefer shade to part-sun.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Begonias in Comal County, TX?

Comal County is in Zone 9a with an average last frost of March 6. Plan your Begonias planting based on this frost date — see the calendar above for exact timing.

What planting zone is Comal County, TX?

Comal County, Texas is in USDA Hardiness Zone 9a. The average last spring frost is March 6 and first fall frost is November 22.

🌱

Your Comal County Garden Planner — Free

A 22-page printable planner built for Comal 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.

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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 Comal County, TX. Local conditions may vary. Last updated: August 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.