When to Plant Cosmos in Tillman County, OK
June in Tillman County, Oklahoma — your action list
Each item below is timed to Tillman County, Oklahoma's frost dates and soil temperatures. Skip nothing, stress about nothing.
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Start harvesting cosmos
Check every 1–2 days. Many of these get tough or go to seed if you wait too long.
July will be here before you know it — start on
- 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.
Tillman County, Oklahoma is in USDA Zone 8a. The average last spring frost is April 3 and the first fall frost is November 6, giving you a growing season of approximately 217 days.
At an elevation of 807 feet, Tillman County receives approximately 25.1 inches of rainfall annually with predominantly loam soil. Summer highs average 88°F, providing good warmth for Cosmos during the growing season.
Tillman County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.5
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 Tillman County
How your county's soil matches Cosmos's growing requirements.
Soil pH
Your soil pH (6.2–7.5) is within Cosmos's preferred range (6.0–8.0).
Soil Texture
The loam soil in Tillman County is excellent for Cosmos — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.6%). Annual compost additions will help Cosmos.
How to Plant Cosmos
Succession Planting Cosmos
Sow every 6.9 weeks. Last sowing by Aug 08 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 | — | 0.6" | 0" | ❄️ Dormant |
| Feb | — | 0.9" | 0" | ❄️ Dormant |
| Mar | — | 1.7" | 0" | ❄️ Dormant |
| Apr | 2.2" | 2.8" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 3.7" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 4" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 3.3" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 2.9" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 2" | 0.2" | 💧 Light watering |
| Oct | 2.2" | 1.6" | 0.6" | 💧 Light watering |
| Nov | 2.2" | 0.8" | 1.4" | 🚿 Regular watering |
| Dec | — | 0.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Nov in Tillman 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 — Tillman County, OK
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 6 | Mar 6 – Mar 20 |
| Transplant Outdoors | March 20 | Mar 20 – Apr 3 |
| Direct Sow | March 20 | Mar 20 – Apr 10 |
| Bloom | May 29 | May 29 – Oct 16 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors Transplant Outdoors Direct Sow |
| April | Transplant Outdoors Direct Sow |
| May | Bloom |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.5"/week · Only during dry spells
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–8 · Your soil: ideal
🗺️ USDA Zone
Zone 8a
📆 Growing Season
217 days in Tillman County
Growing Tips for Cosmos in Tillman County
Direct sow Cosmos outdoors after April 03 in Tillman County when soil has warmed and frost danger has passed.
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 Tillman County, OK?
Tillman County is in Zone 8a with an average last frost of April 3. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Tillman County, OK?
Tillman County, Oklahoma is in USDA Hardiness Zone 8a. The average last spring frost is April 3 and first fall frost is November 6.
Your Tillman County Garden Planner — Free
A 22-page printable planner built for Tillman County (Zone 8a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.