When to Plant Cosmos in Hidalgo County, TX
Your June game plan for Hidalgo County, Texas
Your garden in Hidalgo County, Texas is working on a schedule, even when you're not. Here's where you should be this June.
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Basket week: cosmos
Check every 1–2 days. Many of these get tough or go to seed if you wait too long.
Looking ahead to July
- First harvests: cosmos
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.
Hidalgo County, Texas is in USDA Zone 10a. The average last spring frost is February 6 and the first fall frost is December 18, giving you a growing season of approximately 315 days.
At an elevation of 4,081 feet, Hidalgo County receives approximately 67 inches of rainfall annually with predominantly loam soil. Summer highs average 100°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.
Hidalgo County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.8
Drainage
Well Drained
Cosmos 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 Hidalgo County
How your county's soil matches Cosmos's growing requirements.
Soil pH
Your soil pH (6.2–7.8) is within Cosmos's preferred range (6.0–8.0).
Soil Texture
The loam soil in Hidalgo County is excellent for Cosmos — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.3%). Annual compost additions will help Cosmos.
How to Plant Cosmos
Succession Planting Cosmos
Sow every 6.9 weeks. Last sowing by Sep 19 to harvest before frost.
Cosmos Water Budget
Monthly Watering Guide for Cosmos
Cosmos 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 | Cosmos Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.4" | 0" | ❄️ Dormant |
| Feb | 2.2" | 2.1" | 0.1" | 💧 Light watering |
| Mar | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 6.7" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 10.1" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 9.4" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 9.3" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 8.7" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 6.9" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 4.5" | 0" | ✅ Rainfall sufficient |
| Nov | 2.2" | 2.5" | 0" | ✅ Rainfall sufficient |
| Dec | 2.2" | 1.8" | 0.4" | 💧 Light watering |
Water needs are for active growing months only (Feb–Dec in Hidalgo County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Cosmos 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.
Cosmos Planting Timeline — Hidalgo County, TX
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | January 9 | Jan 9 – Jan 23 |
| Transplant Outdoors | December 26 | Dec 26 – Jan 9 |
| Direct Sow | December 26 | Dec 26 – Jan 16 |
| Bloom | March 6 | Mar 6 – Sep 18 |
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
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–8 · Your soil: ideal
🗺️ USDA Zone
Zone 10a
📆 Growing Season
315 days in Hidalgo County
Growing Tips for Cosmos in Hidalgo County
Direct sow Cosmos outdoors after February 06 in Hidalgo County when soil has warmed and frost danger has passed.
With summer highs reaching 100°F in Hidalgo County, provide afternoon shade for Cosmos and water deeply in the morning.
Common pests for Cosmos 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; 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 Hidalgo County, TX?
Hidalgo County is in Zone 10a with an average last frost of February 6. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Hidalgo County, TX?
Hidalgo County, Texas is in USDA Hardiness Zone 10a. The average last spring frost is February 6 and first fall frost is December 18.
Your Hidalgo County Garden Planner — Free
A 22-page printable planner built for Hidalgo 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.