When to Plant Cosmos in Cameron 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.
Cameron County, Texas is in USDA Zone 10a. The average last spring frost is February 4 and the first fall frost is December 22, giving you a growing season of approximately 321 days.
At an elevation of 4,025 feet, Cameron County receives approximately 58.6 inches of rainfall annually with predominantly loam soil. Summer highs average 103°F, so Cosmos may need afternoon shade and extra watering during peak heat. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Cosmos root diseases.
Cameron County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.8
Drainage
Well Drained
Monthly Watering Guide for Cosmos
Cosmos needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Cosmos Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | 4.3" | 2.2" | 2.1" | 💧 Light watering |
| Mar | 4.3" | 3.1" | 1.2" | 💧 Light watering |
| Apr | 4.3" | 6.1" | 0" | ✅ Rainfall sufficient |
| May | 4.3" | 9.2" | 0" | ✅ Rainfall sufficient |
| Jun | 4.3" | 9.1" | 0" | ✅ Rainfall sufficient |
| Jul | 4.3" | 7.5" | 0" | ✅ Rainfall sufficient |
| Aug | 4.3" | 6.9" | 0" | ✅ Rainfall sufficient |
| Sep | 4.3" | 5.6" | 0" | ✅ Rainfall sufficient |
| Oct | 4.3" | 3.8" | 0.5" | 💧 Light watering |
| Nov | 4.3" | 2.1" | 2.2" | 🚿 Regular watering |
| Dec | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
Water needs are for active growing months only (Feb–Dec in Cameron County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Cosmos Planting Timeline — Cameron County, TX
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 7 | Jan 7 – Jan 21 |
| Transplant Outdoors | December 24 | Dec 24 – Jan 7 |
| Direct Sow | December 24 | Dec 24 – Jan 14 |
| Bloom | March 4 | Mar 4 – 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 | — |
| March | Bloom |
| April | Bloom |
| May | Bloom |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | — |
| November | — |
| December | Transplant Outdoors Direct Sow |
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 10a
📆 Growing Season
321 days in Cameron County
Growing Tips for Cameron 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 Cameron County, TX?
Cameron County is in Zone 10a with an average last frost of February 4. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Cameron County, TX?
Cameron County, Texas is in USDA Hardiness Zone 10a. The average last spring frost is February 4 and first fall frost is December 22.
Your Cameron County Garden Planner — Free
A 22-page printable planner built for Cameron County (Zone 10a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.