When to plant Cosmos in Alpine County, CA
In Alpine County, Cosmos is a spring-only crop. Plant May 19–June 9 once soil hits 50°F.
When to Plant Cosmos in Alpine 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.
Alpine County, California is in USDA Zone 6b. The average last spring frost is May 19 and the first fall frost is October 3, giving you a growing season of approximately 137 days.
At an elevation of 1,278 feet, Alpine County receives approximately 36.3 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Cosmos to ensure they mature before fall.
Alpine County Soil Profile
Soil Type
Loam
Soil pH
6.4-7.3
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 | — | 7.1" | 0" | ❄️ Dormant |
| Feb | — | 8.7" | 0" | ❄️ Dormant |
| Mar | — | 5.7" | 0" | ❄️ Dormant |
| Apr | — | 2.7" | 0" | ❄️ Dormant |
| May | 4.3" | 1" | 3.3" | 🚿 Regular watering |
| Jun | 4.3" | 0.2" | 4.1" | 🚿 Regular watering |
| Jul | 4.3" | 0" | 4.3" | 🚿 Regular watering |
| Aug | 4.3" | 0" | 4.3" | 🚿 Regular watering |
| Sep | 4.3" | 0.3" | 4" | 🚿 Regular watering |
| Oct | 4.3" | 1.6" | 2.7" | 🚿 Regular watering |
| Nov | — | 3.7" | 0" | ❄️ Dormant |
| Dec | — | 5.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Alpine County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Cosmos Planting Timeline — Alpine County, CA
Cosmos Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 21 | Apr 21 – May 5 |
| Transplant Outdoors | May 19 | May 19 – Jun 2 |
| Direct Sow | May 19 | May 19 – Jun 9 |
| Bloom | July 28 | Jul 28 – Nov 10 |
Plant 0.3" deep · 12" apart · Rows 18" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Start Indoors Transplant Outdoors Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | Bloom |
| 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
137 days in Alpine County
Growing Tips for Alpine 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 Alpine County, CA?
Alpine County is in Zone 6b with an average last frost of May 19. Plan your Cosmos planting based on this frost date — see the calendar above for exact timing.
What planting zone is Alpine County, CA?
Alpine County, California is in USDA Hardiness Zone 6b. The average last spring frost is May 19 and first fall frost is October 3.
When should I plant Cosmos in Alpine County, CA?
In Alpine County, CA, plant Cosmos after the last frost (around May 19) and before the first frost (around October 3). Best results when soil holds above 50°F.
What growing zone is Alpine County, CA for Cosmos?
Alpine 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 Alpine County's climate?
Yes — Cosmos grows well in Alpine County's temperate climate. Alpine County averages a 137-day frost-free season, with last frost around May 19 and first frost around October 3.
Your Alpine County Garden Planner — Free
A 22-page printable planner built for Alpine 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.