When to plant Cosmos in Linn County, MO
Spring Cosmos in Linn County goes in April 17–May 8, once nighttime temps stop dipping near freezing.
When to Plant Cosmos in Linn County, MO
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.
Linn County, Missouri is in USDA Zone 6a. The average last spring frost is April 17 and the first fall frost is October 20, giving you a growing season of approximately 186 days.
At an elevation of 880 feet, Linn County receives approximately 32.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Cosmos during the growing season.
Linn County Soil Profile
Soil Type
Silt Loam
Soil pH
5.5-6.8
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 | — | 1.4" | 0" | ❄️ Dormant |
| Feb | — | 1.7" | 0" | ❄️ Dormant |
| Mar | — | 2.4" | 0" | ❄️ Dormant |
| Apr | 4.3" | 2.8" | 1.5" | 💧 Light watering |
| May | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Jun | 4.3" | 3.7" | 0.6" | 💧 Light watering |
| Jul | 4.3" | 3.5" | 0.8" | 💧 Light watering |
| Aug | 4.3" | 3.8" | 0.5" | 💧 Light watering |
| Sep | 4.3" | 2.9" | 1.4" | 💧 Light watering |
| Oct | 4.3" | 2.4" | 1.9" | 💧 Light watering |
| Nov | — | 2.7" | 0" | ❄️ Dormant |
| Dec | — | 1.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Linn County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Cosmos Planting Timeline — Linn County, MO
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 20 | Mar 20 – Apr 3 |
| Transplant Outdoors | April 17 | Apr 17 – May 1 |
| Direct Sow | April 17 | Apr 17 – May 8 |
| Bloom | June 26 | Jun 26 – Oct 2 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Bloom |
| July | Bloom |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| 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 6a
📆 Growing Season
186 days in Linn County
Growing Tips for Linn 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 Linn County, MO?
Linn County is in Zone 6a with an average last frost of April 17. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Linn County, MO?
Linn County, Missouri is in USDA Hardiness Zone 6a. The average last spring frost is April 17 and first fall frost is October 20.
When should I plant Cosmos in Linn County, MO?
In Linn County, MO, plant Cosmos after the last frost (around April 17) and before the first frost (around October 20). Best results when soil holds above 50°F.
What growing zone is Linn County, MO for Cosmos?
Linn County sits in USDA Zone 6a. Cosmos grows reliably in zones 2a through 11b, so it's a good fit here.
Can Cosmos grow in Linn County's climate?
Yes — Cosmos grows well in Linn County's temperate climate. Linn County averages a 186-day frost-free season, with last frost around April 17 and first frost around October 20.
Your Linn County Garden Planner — Free
A 22-page printable planner built for Linn County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.