When to Plant Sunflower in Guadalupe County, TX
Sunflowers are tall, cheerful annuals grown for their edible seeds and as pollinator magnets. They come in sizes from 2-foot dwarfs to 12-foot giants.
Guadalupe County, Texas is in USDA Zone 8b. The average last spring frost is March 7 and the first fall frost is November 21, giving you a growing season of approximately 259 days.
At an elevation of 3,679 feet, Guadalupe County receives approximately 63 inches of rainfall annually with predominantly clay soil. Summer highs average 93°F, providing good warmth for Sunflower during the growing season. Clay soil retains moisture well for Sunflower, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Sunflower root diseases.
Guadalupe County Soil Profile
Soil Type
Clay
Soil pH
6.9-8.2
Drainage
Well Drained
Plant Planting Risk Windows
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 Guadalupe County
How your county's soil matches Sunflower's growing requirements.
Soil pH
Your soil pH (6.9–8.2) is more alkaline than Sunflower prefers (6.0–7.5). Add sulfur or peat moss to lower pH.
Soil Texture
Your clay soil in Guadalupe County is workable for Sunflower. Add compost annually to improve structure.
Organic Matter
Organic matter is moderate (2.7%). Annual compost additions will help Sunflower.
How to Plant Sunflower
Succession Planting Sunflower
Sow every 8 weeks. Last sowing by Aug 13 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Sunflower
Sunflower needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Sunflower Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 2.1" | 0" | ❄️ Dormant |
| Mar | 2.2" | 4.4" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 6.5" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 9.5" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 9.3" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 8" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 7.1" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 6.4" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 4.5" | 0" | ✅ Rainfall sufficient |
| Nov | 2.2" | 1.9" | 0.3" | 💧 Light watering |
| Dec | — | 1.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Guadalupe County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Sunflower 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.
Sunflower Planting Timeline — Guadalupe County, TX
Sunflower Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 17 | Jan 17 – Jan 31 |
| Transplant Outdoors | March 21 | Mar 21 – Apr 4 |
| Direct Sow | March 14 | Mar 14 – Apr 4 |
| Harvest | May 30 | May 30 – Jul 18 |
Plant 1" deep · 18" apart · Rows 30" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors |
| February | — |
| March | Transplant Outdoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | Harvest |
| June | Harvest |
| July | Harvest |
| August | — |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
70–100 days
🧪 Soil pH
Needs 6–7.5 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 8b
📆 Growing Season
259 days in Guadalupe County
Growing Tips for Sunflower in Guadalupe County
Direct sow Sunflower outdoors after March 07 in Guadalupe County when soil has warmed and frost danger has passed.
With Guadalupe County's clay soil (40% clay), work in 3-4 inches of compost before planting Sunflower. Avoid tilling when soil is wet to prevent compaction.
Common pests for Sunflower in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
General growing tips
Direct sow after last frost. Stake tall varieties in windy areas. Harvest seed heads when the back turns brown and seeds are plump. Dry heads upside down.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Sunflower in Other Locations
Frequently Asked Questions
When should I plant Sunflower in Guadalupe County, TX?
Guadalupe County is in Zone 8b with an average last frost of March 7. Plan your Sunflower planting based on this frost date — see the calendar above for exact timing.
What planting zone is Guadalupe County, TX?
Guadalupe County, Texas is in USDA Hardiness Zone 8b. The average last spring frost is March 7 and first fall frost is November 21.
Plan Your Garden with Confidence
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