When to plant Cosmos in Grant County, AR
Grant County sits in USDA Zone 8a. Plant Cosmos between March 6 (after last frost on March 20) and March 27.
When to Plant Cosmos in Grant County, AR
This month in Grant County, Arkansas
Each item below is timed to Grant County, Arkansas's frost dates and soil temperatures. Skip nothing, stress about nothing.
-
It's harvest week for cosmos
Check every 1–2 days. Many of these get tough or go to seed if you wait too long.
July prep starts now
- 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.
Grant County, Arkansas is in USDA Zone 8a. The average last spring frost is March 20 and the first fall frost is November 11, giving you a growing season of approximately 236 days.
At an elevation of 498 feet, Grant County receives approximately 51.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 94°F, providing good warmth for Cosmos during the growing season. Ample rainfall means less supplemental watering, but ensure good drainage to prevent Cosmos root diseases.
Grant County Soil Profile
Soil Type
Silt Loam
Soil pH
5.3-6.6
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 Grant County
How your county's soil matches Cosmos's growing requirements.
Soil pH
Your soil pH (5.3–6.6) is more acidic than Cosmos prefers (6.0–8.0). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Grant County is excellent for Cosmos — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.7%). Annual compost additions will help Cosmos.
How to Plant Cosmos
Succession Planting Cosmos
Sow every 6.9 weeks. Last sowing by Aug 13 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 | — | 3.9" | 0" | ❄️ Dormant |
| Feb | — | 4.6" | 0" | ❄️ Dormant |
| Mar | 2.2" | 4.4" | 0" | ✅ Rainfall sufficient |
| Apr | 2.2" | 3.8" | 0" | ✅ Rainfall sufficient |
| May | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| Jun | 2.2" | 4.2" | 0" | ✅ Rainfall sufficient |
| Jul | 2.2" | 5" | 0" | ✅ Rainfall sufficient |
| Aug | 2.2" | 5.5" | 0" | ✅ Rainfall sufficient |
| Sep | 2.2" | 3.6" | 0" | ✅ Rainfall sufficient |
| Oct | 2.2" | 3.7" | 0" | ✅ Rainfall sufficient |
| Nov | 2.2" | 4.4" | 0" | ✅ Rainfall sufficient |
| Dec | — | 4.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in Grant 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 — Grant County, AR
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 20 | Feb 20 – Mar 6 |
| Transplant Outdoors | March 6 | Mar 6 – Mar 20 |
| Direct Sow | March 6 | Mar 6 – Mar 27 |
| Bloom | May 15 | May 15 – Oct 2 |
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
0.5"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–8 · Your soil: too_acidic
🗺️ USDA Zone
Zone 8a
📆 Growing Season
236 days in Grant County
Growing Tips for Cosmos in Grant County
Direct sow Cosmos outdoors after March 20 in Grant 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 Grant County, AR?
Grant County is in Zone 8a with an average last frost of March 20. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Grant County, AR?
Grant County, Arkansas is in USDA Hardiness Zone 8a. The average last spring frost is March 20 and first fall frost is November 11.
When should I plant Cosmos in Grant County, AR?
In Grant County, AR, plant Cosmos after the last frost (around March 20) and before the first frost (around November 11). Best results when soil holds above 50°F.
What growing zone is Grant County, AR for Cosmos?
Grant County sits in USDA Zone 8a. Cosmos grows reliably in zones 2a through 11b, so it's a good fit here.
Can Cosmos grow in Grant County's climate?
Yes — Cosmos grows well in Grant County's temperate climate. Grant County averages a 236-day frost-free season, with last frost around March 20 and first frost around November 11.
Your Grant County Garden Planner — Free
A 22-page printable planner built for Grant 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.