When to Plant Cosmos in San Jacinto County, TX
Cosmos (Cosmos bipinnatus) is an airy, feathery-foliaged cottage garden annual from Mexico that thrives on neglect. It produces delicate daisy-like blooms in shades of pink, white, and magenta from midsummer until frost. Cosmos is a prolific self-sower — once established in a garden it often returns year after year without replanting. Excellent habitat plant for beneficial insects.
San Jacinto 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 6 feet, San Jacinto County receives approximately 71.3 inches of rainfall annually with predominantly sandy loam soil. Summer highs average 94°F, providing good warmth for Cosmos during the growing season. Sandy soil warms quickly in spring — great for early planting — but Cosmos will need more frequent watering and organic matter to retain nutrients. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Cosmos root diseases.
San Jacinto County Soil Profile
Soil Type
Sandy Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Cosmos Planting Timeline — San Jacinto County, TX
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 21 | Jan 21 – Feb 4 |
| Transplant Outdoors | January 21 | Jan 21 – Feb 4 |
| Direct Sow | January 21 | Jan 21 – Feb 11 |
| Bloom | April 1 | Apr 1 – Sep 16 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors Direct Sow |
| February | Start Indoors 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
Low — drought tolerant
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–8 · Your soil: N/A
🗺️ USDA Zone
Zone 9a
📆 Growing Season
286 days in San Jacinto County
Growing Tips for San Jacinto County
Direct-sow after last frost; cosmos germinates readily at 65-80°F in 7-10 days. Avoid rich soil — excess fertility produces lush foliage at the expense of blooms. Cosmos tolerates poor, dry soil exceptionally well. Pinch seedlings at 8 inches to encourage branching. Self-sows freely; allow some seed heads to mature and drop for a no-fuss perennial effect in warm climates.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Cosmos in Other Locations
Frequently Asked Questions
When should I plant Cosmos in San Jacinto County, TX?
San Jacinto County is in Zone 9a with an average last frost of February 18. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is San Jacinto County, TX?
San Jacinto County, Texas is in USDA Hardiness Zone 9a. The average last spring frost is February 18 and first fall frost is December 1.
Your San Jacinto County Garden Planner — Free
A 22-page printable planner built for San Jacinto 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.