When to plant Cosmos in Modoc County, CA
In Modoc County, Cosmos is a single-season spring crop — there's no second fall window. Plant May 31–June 21 for an 60–90-day harvest, finishing well before the September 21 first frost.
When to Plant Cosmos in Modoc County, CA
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.
Modoc County, California is in USDA Zone 6b. The average last spring frost is May 31 and the first fall frost is September 21, giving you a growing season of approximately 113 days.
At an elevation of 2,205 feet, Modoc County receives approximately 28.3 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Cosmos to ensure they mature before fall.
Modoc County Soil Profile
Soil Type
Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Cosmos Planting Timeline — Modoc County, CA
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | May 3 | May 3 – May 17 |
| Transplant Outdoors | May 31 | May 31 – Jun 14 |
| Direct Sow | May 31 | May 31 – Jun 21 |
| Bloom | August 9 | Aug 9 – Nov 22 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Start Indoors Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Bloom |
| September | Bloom |
| October | Bloom |
| November | Bloom |
| 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 6b
📆 Growing Season
113 days in Modoc County
Growing Tips for Modoc 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 Modoc County, CA?
Modoc County is in Zone 6b with an average last frost of May 31. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Modoc County, CA?
Modoc County, California is in USDA Hardiness Zone 6b. The average last spring frost is May 31 and first fall frost is September 21.
When should I plant Cosmos in Modoc County, CA?
In Modoc County, CA, plant Cosmos after the last frost (around May 31) and before the first frost (around September 21). Best results when soil holds above 50°F.
What growing zone is Modoc County, CA for Cosmos?
Modoc County sits in USDA Zone 6b. Cosmos grows reliably in zones 2a through 11b, so it's a good fit here.
Can Cosmos grow in Modoc County's climate?
Yes — Cosmos grows well in Modoc County's temperate climate. Modoc County averages a 113-day frost-free season, with last frost around May 31 and first frost around September 21.
Your Modoc County Garden Planner — Free
A 22-page printable planner built for Modoc County (Zone 6b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.