When to Plant Zinnia in Tarrant County, TX
Zinnia (Zinnia elegans) is a fast-growing, heat-loving annual that produces bold, dahlia-like blooms from early summer until hard frost. One of the easiest flowers to grow from direct-sown seed, zinnias thrive in hot, dry conditions and are magnets for butterflies and beneficial insects. They make excellent companion plants alongside marigolds in the vegetable garden.
Tarrant County, Texas is in USDA Zone 8b. The average last spring frost is March 18 and the first fall frost is November 12, giving you a growing season of approximately 239 days.
At an elevation of 3,487 feet, Tarrant County receives approximately 63.1 inches of rainfall annually with predominantly clay soil. Summer highs average 92°F, providing good warmth for Zinnia during the growing season. Clay soil retains moisture well for Zinnia, but amend with compost to improve drainage and prevent root rot. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Zinnia root diseases.
Tarrant County Soil Profile
Soil Type
Clay
Soil pH
7.3-8.1
Drainage
Well Drained
Monthly Watering Guide for Zinnia
Zinnia needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Zinnia Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.8" | 0" | ❄️ Dormant |
| Feb | — | 2.2" | 0" | ❄️ Dormant |
| Mar | 4.3" | 3.8" | 0.5" | 💧 Light watering |
| Apr | 4.3" | 7" | 0" | ✅ Rainfall sufficient |
| May | 4.3" | 9.8" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 10.1" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 7.2" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 8.1" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 5.5" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 4.1" | 0.2" | 💧 Light watering |
| Nov | 4.3" | 2.2" | 2.1" | 💧 Light watering |
| Dec | — | 1.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Tarrant County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Zinnia Planting Timeline — Tarrant County, TX
Zinnia Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 18 | Feb 18 – Mar 4 |
| Transplant Outdoors | March 4 | Mar 4 – Mar 18 |
| Direct Sow | March 4 | Mar 4 – Mar 25 |
| Bloom | May 13 | May 13 – Oct 14 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors Transplant Outdoors Direct Sow |
| April | — |
| May | Bloom |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Low — drought tolerant
📅 Days to Maturity
60–70 days
🧪 Soil pH
Needs 5.5–7.5 · Your soil: N/A
🗺️ USDA Zone
Zone 8b
📆 Growing Season
239 days in Tarrant County
Growing Tips for Tarrant County
Direct-sow after last frost when soil reaches 60°F; seeds germinate in 5-7 days. In zones 3-5 a brief indoor start (4 weeks) is worthwhile but transplant carefully — zinnias dislike root disturbance. Deadhead frequently to extend bloom. Excellent cut flower; harvesting regularly encourages branching. Avoid overhead watering to reduce powdery mildew.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Zinnia in Other Locations
Frequently Asked Questions
When should I plant Zinnia in Tarrant County, TX?
Tarrant County is in Zone 8b with an average last frost of March 18. Plan your Zinnia planting based on this frost date — see the calendar above for exact timing.
What planting zone is Tarrant County, TX?
Tarrant County, Texas is in USDA Hardiness Zone 8b. The average last spring frost is March 18 and first fall frost is November 12.
Your Tarrant County Garden Planner — Free
A 22-page printable planner built for Tarrant County (Zone 8b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.